This PDF file contains the front matter associated with SPIE Proceedings Volume 10526, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

GaAs-based quantum dot (QD) semiconductor lasers at 1300 nm exhibit a number of benefits for use in metropolitan and local area networks. Low modulation-induced chirp attributed to small linewidth enhancement factor (LEF) in QDs overcomes some limitations in a directly-modulated laser compared to quantum well counterparts. Along with the temperature-insensitive low threshold current, these QD lasers demonstrate considerable prospects towards Peltier-free direct-modulation operation. In this work, we experimentally investigate the temperature-dependence of the LEF as a function of injection current and wavelength in state-of-the-art 1300 nm In(Ga)As/GaAs QD lasers grown by molecular beam epitaxy. These structures demonstrate a large state separation and a comparatively small inhomogeneous linewidth. Gain is measured using the Hakki-Paoli method and carrier related mode shift is extracted by correcting for thermal effects. Previous reports have described LEF values of 1-5 over smaller temperature ranges (20-85°C) than the GPON commercial specifications in 1300 nm In(Ga)As/GaAs QD structures. Here, at temperature range of -10 to 85°C extending beyond GPON commercial window, it is shown that even at higher temperatures where contribution from the excited state transition is expected to increase the LEF, the measured LEF remains essentially zero. This is ascribed to the large gain from the ground state transition. Such a low LEF at elevated temperatures bodes well for the use of such structures in applications where feedback insensitivity may be important. By analyzing individual modes as a function of their individual lasing thresholds, we also describe an interplay of mode position and lasing linewidth.

The design of electrically driven quantum light sources based on semiconductor quantum dots, such as singlephoton emitters and nanolasers, asks for modeling approaches combining classical device physics with cavity quantum electrodynamics. In particular, one has to connect the well-established fields of semi-classical semiconductor transport theory and the theory of open quantum systems. We present a first step in this direction by coupling the van Roosbroeck system with a Markovian quantum master equation in Lindblad form. The resulting hybrid quantum-classical system obeys the fundamental laws of non-equilibrium thermodynamics and provides a comprehensive description of quantum dot devices on multiple scales: It enables the calculation of quantum optical figures of merit (e.g. the second order intensity correlation function) together with the spatially resolved simulation of the current flow in realistic semiconductor device geometries in a unified way.

An analytical model for operating characteristics of a novel type of semiconductor lasers, quantum dot (QD) lasers with asymmetric barrier layers (ABLs), is discussed. In such lasers, the ABLs (one on each side of the active layer with QDs) should ideally keep the electron-injecting side of the structure completely devoid of holes and the hole-injecting side devoid of electrons thus eliminating the parasitic electron-hole recombination there. In actual structures, however, the ABLs will only partly fulfill this function; as a result, there will be a certain fraction of electrons on the hole-injecting side and holes on the electron-injecting side and, hence, the parasitic electron-hole recombination will still occur outside QDs in addition to the useful electron-hole recombination in QDs. In this work, the effect of non-ideality of ABLs on threshold and high-power characteristics of ABL QD lasers is theoretically studied. The extent, to which the laser operating characteristics are affected, is quantified by deriving and analyzing closed-form expressions for the threshold current density, characteristic temperature, internal differential quantum efficiency, and output optical power as functions of non-ideality of ABLs. Approaches for optimizing the ABL QD lasers performance are discussed.

We present an analysis of Quantum Dot (QD) based Push-Pull modulated DFB (PP-DFB) laser, showing enhanced small and large signal modulation bandwidth thanks to the interaction between two longitudinal cavity modes. Using an analysis of the cavity modes at threshold, we propose a simple yet effective design technique which allow to select the cavity length and the coupling coefficient to obtain the desired extension of the modulation bandwidth. The design is validated using a Time Domain Travelling Wave (TDTW) model including a proper description of the Quantum Dot material and of the standing wave pattern generated by the cavity field. Our results show that QD PP-DFB can effectively take advantage of the Push-Pull modulation scheme to increase their modulation bandwidth.

This work theoretically investigates the four-level pulse-amplitude modulation characteristics of quantum dot lasers subject to optical injection. The rate equation model takes into account carrier dynamics in the carrier reservoir, in the excited state, and in the ground state, as well as photon dynamics and phase dynamics of the electric field. It is found that the optical injection significantly improves the eye diagram quality through suppressing the relaxation oscillation, while the extinction ratio is reduced as well. In addition, both the adiabatic chirp and the transient chirp of the signal are substantially suppressed.

We propose a method to use artificial neural networks to approximate light scattering by multilayer nanoparticles. We find the network needs to be trained on only a small sampling of the data in order to approximate the simulation to high precision. Once the neural network is trained, it can simulate such optical processes orders of magnitude faster than conventional simulations. Furthermore, the trained neural network can be used solve nanophotonic inverse design problems by using back-propogation - where the gradient is analytical, not numerical.

Localized surface plasmons (LSP) can be excited in metal nanoparticles (NP) by UV, visible or NIR light and are described as coherent oscillation of conduction electrons. Taking advantage of the tunable optical properties of NPs, we propose the realization of a plasmonic structure, based on the LSP interaction of NP with an embedding matrix of amorphous silicon. This study is directed to define the characteristics of NP and substrate necessary to the development of a LSP proteomics sensor that, once provided immobilized antibodies on its surface, will screen the concentration of selected antigens through the determination of LSPR spectra and peaks of light absorption. Metals of interest for NP composition are: Aluminium and Gold. Recent advances in nanoparticle production techniques allow almost full control over shapes and size, permitting full control over their optical and plasmonic properties and, above all, over their responsive spectra. Analytical solution is only possible for simple NP geometries, therefore our analysis, is realized recurring to computer simulation using the Discrete Dipole Approximation method (DDA). In this work we use the free software DDSCAT to study the optical properties of metal nanoparticles embedded in an amorphous silicon matrix, as a function of size, shape, aspect-ratio and metal type. Experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.

Porous TiO₂ films are a crucial part of mesostructured solar cells (MSCs), both dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). However, the literature does not provide a clear description of the optical properties especially of the refractive index and scattering for those films relevant to MSCs. In DSSCs, two different porous TiO₂ layers are included, the mesoporous active layer and the blocking layer. While the first is essential for the charge separation, electron collection and ion conduction, the second is intended for suppressing the loss of generated electrons to the electrolyte. Both layers consist of the same chemical compound, TiO₂, but they have different porosities. For PSCs, the perovskite is deposited on a mesoporous TiO₂ structure for enhancing the I–V characteristics

This paper investigates TiO₂ films really used in fabricated MSCs. We utilize a technique allowing the determination of the effective refractive index and the film porosity for two different film kinds fabricated using sol-gel methods, discussed in our previous work, to determine the thickness of TiO₂ films typically used in fabricating MSCs.

Recent advances in sub-wavelength nanoscale platforms have afforded the control of light from first principles, with impact to ultrafast sciences, optoelectronics and precision measurements. In this talk we will describe recent advances in chip-scale Kerr frequency comb oscillators, where we have achieved sub-100-fs mode-locking, stabilization down to a tooth-to-tooth relative frequency uncertainty of 50 mHz and 2.7×10^{−16}, and single-mode broadband frequency comb generation. Each of these are supported by linear and nonlinear numerical modeling. In this first chip-scale realization, coherent mode-locking is observed in the normal dispersion regime, verified by phase-resolved ultrafast spectroscopy at sub-100-attojoule sensitivities. The normal dispersion architecture uncovers the mode-locking mechanisms in Kerr frequency combs, matched with first-principles coupled-mode theory. In the second realization, we examine the noise limits in the full stabilization of chip-scale optical frequency combs. The microcomb’s two degrees of freedom, one of the comb lines and the native 18-GHz comb spacing, are simultaneously phase-locked to known optical and microwave references. Active comb spacing stabilization improves long-term stability by six orders of magnitude, reaching a record instrument-limited residual instability of 3.6 mHz per root tau. Comparing 46 nitride frequency comb lines with a benchmark fiber laser frequency comb, we demonstrate the unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7×10^{−16}. In the third realization, we report a novel design of Si3N4 microresonator in which single-mode operation, high quality factor, and anomalous dispersion are attained simultaneously. The novel microresonator consists of uniform single-mode waveguides in the semi-circle region, to eliminate bending induced mode coupling, and adiabatically tapered waveguides in the straight region, to avoid excitation of higher order modes. With this microresonator, we demonstrate broadband phase-locked frequency combs. This supports the focus towards chip-scale precision spectroscopy, timing, coherent communications, and astronomical spectrography.

Extreme events are characterized by rare and high amplitude excursions of a given variable characterizing a physical system with respect to its long time average. Its study in optics has been primarily motivated by the analogy with rogue waves in hydrodynamics and includes ingredients such as spatial instabilities, nonlinearities and noise. Here we consider a spatially extended microcavity laser with integrated saturable absorber in the self-pulsing regime. This system, thanks to its short typical timescales, allows large recordings and accurate statistics. Moreover, it does not display irregular or aperiodic dynamics without spatial coupling. Hence, the role of spatial coupling in the emergence of extreme events can be studied. With the help of a model and of numerical analysis together with the experimental observations, we unveil the dynamical origin of the extreme events in the occurrence of spatiotemporal chaos [1], rather than through collisions of coherent structures. Moreover, by investigating the fine structure of the maximum Lyapunov exponent, of the Lyapunov spectrum and of the Kaplan-Yorke dimension of the chaotic attractor, we are able to deduce that intermittency plays a key role in the proportion of extreme events measured. We assign the observed mechanism of generation of extreme events to quasi-periodic extended spatiotemporal intermittency [2]. The understanding of the formation mechanism of these extreme phenomena is an important step to devise strategies to control them. [1] Selmi et al, Phy. Rev. Lett. 116, 013901 (2016). [2] Coulibaly et al, Phys. Rev. A 95, 023816 (2017).

An inordinate amount of time, effort (and paper) has been spent trying to find a way to stabilize laser-diode frequencies, but our research team has been working on the premise, that frequency instability can, in fact, have its up-sides. In the present work, we focus on a method that uses laser diodes’ own noise to generate physical random numbers. Introducing a frequency discriminator as a reference, we control and stabilize the difference between the frequency reference and the laser frequency, thereby generating random numbers at a suitable point.

Directly-modulated lasers remain excellent candidates for the development of efficient and low-cost short communication links. While the modulation bandwidth of semiconductor lasers is inherently limited by the relaxation oscillations due carrier-photon interaction, it is possible to further enhance the modulation dynamics by using nonlinear architectures. Our recent studies has revealed the high potential of the optically injection-locked semiconductor laser operating under gain lever effect. Modulation bandwidth as large as 85 GHz namely four times larger than that of the free-running semiconductor laser has been unveiled. In this work, we numerically investigate the large-signal capabilities of this transmitter by evaluating eye diagrams and bit error rates. The results confirm its high potential for short communication links operating at high-speeds.

We present a theoretical study of a many-emitter phonon laser based on optically driven semiconductor quantum dots placed within an acoustic nanocavity. A transformation of the phonon laser Hamiltonian leads to a Tavis-Cummings type interaction with an unexpected additional many-emitter energy shift. This many-emitter interaction with the cavity mode results in a variety of phonon resonances which dependent strongly on the number of participating emitters. These collective resonances show the highest phonon output. Furthermore, we show that the output can be increased even more via lasing at the two phonon resonance.

In this paper, we see a strong effect of the injected current on the light emission from the polariton condensate in an n-i-n structure, when we monitor the luminescence intensity under applied bias at various pump powers. We present here three thresholds for nonlinear increase of the intensity. We show that small changes of the incoherent injected current lead to stimulated enhancement of the coherent light emission from free carriers. We conclude that the polariton condensatecurrent system is a highly nonlinear electro-optical system.

The development and physical understanding of high-beta nanolasers operating in regime of cavity-quantum-electrodynamics (cQED) is a highly interdisciplinary field of research, involving important aspects of nanotechnology, quantum optics, and semiconductor physics. Of particular interest is the quantum limit of operation, in which a few or even a single emitter act as gain material. The regime of strong light-matter coupling is typically associated with weak excitation. With current realizations of cQED systems, strong coupling may persevere even at elevated excitation levels sufficient to cross the threshold to lasing. In the presence of stimulated emission, the vacuum-Rabi doublet in the emission spectrum is modified and the established criterion for strong coupling no longer applies. Based on an analytic approach, we provide a generalized criterion for strong coupling and the corresponding emission spectrum that includes the influence of higher Jaynes-Cummings states. The applicability is demonstrated in a theory-experiment comparison of a state-of-the-art few-emitter quantum-dot (QD)–micropillar laser as a particular realization of the driven dissipative Jaynes-Cummings model [1]. Furthermore, we address the question if and for which parameters true single-emitter lasing can be achieved. By using a master-equation approach for up to 8 QDs coupled to the mode, we provide evidence for the coexistence of strong coupling and lasing in our system in the presence of background emitter contributions by identifying signatures in the mean-photon number, the photon-autocorrelation function, and the emission linewidth. [1] C. Gies et al., accepted for publication in PRA, arxiv:1606.05591

The formation of half-light half-matter quasiparticle exciton polariton and its condensation in semiconductor microcavities are striking phenomena for the macroscopically quantum coherence at elevated temperature. The matter constituent of exciton polariton dictates the interacting behaviors of these bosonic particles primarily via exciton-exciton interactions. However, these interactions are all limited to the ground state exciton, although they are expected to be much stronger at Rydberg states with higher principal numbers. Here, for the first time, we observe the spontaneous formed Rydberg exciton polaritons (REPs) in a high quality Fabry-Perot cavity embedded with single crystal inorganic perovskite. Such REPs exhibit strong nonlinear behavior and anisotropic, enabling an anomalous dynamic process that leads to a coherent polariton condensate with prominent blue shift. This discovery presents a unique platform to study quantum coherent many-body physics, and enables unprecedented manipulation of these Rydberg states by new means such as chemical composition engineering, structural phase control, and external gauge fields. The solid state REP and its condensates also hold great potential for important applications, such as sensing, communication, and quantum computing.

This talk will present a tutorial discuss of several important aspects of recent progress on semiconductor nanolasers. After some general introduction, the talk will be divided into the discussions of two types of nanolasers: 1) nanolasers based on plasmonic structures or metallic cavities and 2) nanocavities integrated with two-dimensional (2D) monolayer of transition metal dichalcogenides (TMCs). In the first part, we discuss the nanolasers with a metallic or plasmonic cavities. The inclusion of metallic structures or cavities allows reduction of laser sizes significantly below the those of typical pure semiconductor cavities. Such lasers might be potentially important for applications where laser size is the primary concerns, such as in future integrated photonic systems or optical interconnects on the chip. After the review of past progress, we will present some of our recent work on nano-membrane lasers and on plasmonic nano-disk lasers. The second part will deal with the most recent progress in integrating the thinnest gain medium, the 2D monolayer TMCs, with nanolaser cavities. The most exciting aspect of this type of new materials is their strong exciton bonds with binding energy exceeding 0.5 eV, allowing robust excitonic light emission well above room temperature. Integration of such monolayer with a silicon nanobeam cavity has resulted in our recent demonstration of room temperature lasing based on a single layer of TMCs, because of strong excitonic emission and high optical gain. Such silicon compatible lasers might provide an important alternative for high energy-efficiency applications in silicon integrated photonics.

Photonic crystal surface emitting lasers (PCSEL) are of interest in order to achieve large area single mode operation, excellent beam quality, and high output powers. Coherent PCSEL arrays have also been realised and lasing mode control of PCSELs has been demonstrated by using external in-plane feedback. However, the design and analysis of PCSELs has been limited by current modelling techniques. The plane wave expansion method is only applicable to infinite structures whilst the finite difference time domain method is computationally intensive especially when modelling large area, three dimensional finite devices. Other analytical approach, such as coupled mode analysis, leads to significant mathematical complication. None of these are well suited to accurately describing complex PCSEL devices, nor the effect of in-plane feedback. We introduce a general quasi-analytical model based on the separation of variables and a quasi-scalar field distribution. The multilayer planar structure in the growth direction is accounted for by computing the effective indices corresponding to the in-plane bound guided modes. This operation results in a sculpted, periodic index distribution. Next, by first assuming index uniformity along the z-axis, a piecewise constant multilayer periodic media results. An effective wave impedance of the waves supported in this structure are then computed and used to construct the 3D device. In this way, the final device characteristics account for the 2D periodic photonic crystal media. We compare our modelling to other methods, and various experimental reports. In particular we focus upon the effect of external in-plane feedback on PCSELs.

The optical mode properties of an anisotropic nano-layered aluminum-doped zinc oxide rectangular waveguides at the epsilon-near-zero spectral point are numerically investigated. The finite element method is used for a numerical study of the optical resonance frequencies for a square Al:ZnO/ZnO waveguide (1 μm width/height). Optical permittivity for multilayered Al:ZnO/ZnO is described using an effective medium approximation. Our numerical finite element method calculations predict a significant spectral shift, a modified free spectral range, and an asymmetric electric field distribution for lower order optical modes. Those modes have resonance wavelengths at the epsilon-near-zero point (~ 1800 nm). We show that the resonant frequency for the lower order TE₁₁ mode increases dramatically compared to the non-doped zinc-oxide waveguides, while the higher order modes (e.g, TE₂₁) remain almost at the same frequency. This results in less than a 5% difference in resonance frequencies for these two modes for Al:ZnO/ZnO square waveguide.

Bragg mirrors are 1D photonic crystals made of a periodic stack of high and low refractive thin film materials that reflect only a small bandwidth of the spectrum. Such high-reflective devices are commercially available in the visible spectrum at relatively low costs. Functional Bragg mirrors for IR applications are greatly desired, but there exist challenges due to the limited availability of inexpensive, high refractive index, and transparent IR materials. Here, we present the design of high reflectivity Bragg mirrors working in the near and mid-IR range. Our mirror designs use the refractive index values of novel ultrahigh refractive index IR materials known as chalcogenide hybrid inorganic/organic polymers (CHIPs). CHIPs are synthetized from an inverse vulcanization process for elemental sulfur and selenium as reported by the Pyun group [1]. We integrate the optical properties of these materials and those of different low refractive index materials to generate various Bragg mirror designs. The extinction coefficients derived from absorption plots are also taken into account to increase accuracy. The theoretical values for reflectivity, physical thickness, and optical bandwidth are reported, as well as preliminary experimental results. We also present changes in reflectivity and bandwidth due to layer thickness variability. These IR Bragg mirrors have applications in devices and industries which require the use of specific wavelengths in the near and mid-IR range, such as beam-splitters, filters, anti-reflection coatings, etc.

The propagation of electromagnetic fields through inhomogeneous media is an essential requirement in the modeling and design of optoelectronic devices. In the most general case, this requires the application of finite-difference techniques in frequency or time domain, or other rigorous solutions of Maxwell’s equations, which often results in too high a numerical effort for practical applications. However, if the inhomogeneity is represented by a smoothly varying refractive index, e.g. in a GRIN lens, fiber, or acousto-optic modulator, the propagation of the electromagnetic fields can be modeled by fast algorithms. They are based on recent major achievements in fast physical optics and make use of the identification of the diffractive and geometric zones of electromagnetic fields. Dependent on the situation, this can enable vectorial propagation through graded-index media in seconds, including even the crosstalk between polarization directions. The theory and the resulting algorithms include established beam propagation techniques as special cases, e.g. the popular paraxial split-step technique.

A novel Digital Micromirror Device (DMD) based beam steering enables a single chip Light Detection and Ranging (LIDAR) system for discrete scanning points. We present increasing number of scanning point by using multiple laser diodes for Multi-beam and Single-chip DMD-based LIDAR.

Conventional theories of electromagnetic waves in a medium assume that only the energy of the field propagates inside the medium. Consequently, they neglect the transport of mass density by the medium atoms. We have recently presented foundations of a covariant theory of light propagation in a nondispersive medium by considering a light wave simultaneously with the dynamics of the medium atoms driven by optoelastic forces [Phys. Rev. A 95, 063850 (2017)]. In particular, we have shown that the mass is transferred by an atomic mass density wave (MDW), which gives rise to mass-polariton (MP) quasiparticles, i.e., covariant coupled states of the field and matter having a nonzero rest mass. Another key observation of the mass-polariton theory of light is that, in common semiconductors, most of the momentum of light is transferred by moving atoms, e.g., 92% in the case of silicon. In this work, we generalize the MP theory of light for dispersive media and consider experimental measurement of the mass transferred by the MDW atoms when an intense light pulse propagates in a silicon fiber. In particular, we consider optimal intensity and time dependence of a Gaussian pulse and account for the breakdown threshold irradiance of the material. The optical shock wave property of the MDW, which propagates with the velocity of light instead of the velocity of sound, prompts for engineering of novel device concepts like very high frequency mechanical oscillators not limited by the acoustic cutoff frequency.

While standard laser range finders use modulation signals, such as sharp pulses, the method we devised employs laser diode's frequency noise, and a frequency discriminator, to produce the intensity noise signal, which we use to generate fast physical random numbers. Observed through a frequency discriminator, beams traveling along two different paths share intensity noise patterns, i.e., the same fast physical random numbers, but with a time lag. We compared the two, and calculated their cross-correlation. By sweeping their time lags, we confirmed the length of the two optical paths, up to 50m.

Sensors based on fiber optics are irreplaceable wherever immunity to strong electro-magnetic fields or safe operation in explosive atmospheres is needed. Furthermore, it is often essential to be able to monitor high temperatures of over 500°C in such environments (e.g. in cooling systems or equipment monitoring in power plants). In order to meet this demand, we have designed and manufactured a fiber optic sensor with which temperatures up to 900°C can be measured. The sensor utilizes multi-core fibers which are recognized as the dedicated medium for telecommunication or shape sensing, but as we show may be also deployed advantageously in new types of fiber optic temperature sensors. The sensor presented in this paper is based on a dual-core microstructured fiber Michelson interferometer. The fiber is characterized by strongly coupled cores, hence it acts as an all-fiber coupler, but with an outer diameter significantly wider than a standard fused biconical taper coupler, which significantly increases the coupling region’s mechanical reliability. Owing to the proposed interferometer imbalance, effective operation and high-sensitivity can be achieved. The presented sensor is designed to be used at high temperatures as a result of the developed low temperature chemical process of metal (copper or gold) coating. The hermetic metal coating can be applied directly to the silica cladding of the fiber or the fiber component. This operation significantly reduces the degradation of sensors due to hydrolysis in uncontrolled atmospheres and high temperatures.

Extinction ratio is an inherent limiting factor that has a direct effect on the detection performance of phase-OTDR based distributed acoustics sensing systems. In this work we present a model based analysis of Rayleigh scattering to simulate the effects of extinction ratio on the received signal under varying signal acquisition scenarios and system parameters. These signal acquisition scenarios are constructed to represent typically observed cases such as multiple vibration sources cluttered around the target vibration source to be detected, continuous wave light sources with center frequency drift, varying fiber optic cable lengths and varying ADC bit resolutions. Results show that an insufficient ER can result in high optical noise floor and effectively hide the effects of elaborate system improvement efforts.

Single-photon avalanche diodes (SPADs) have been widely used to push the frontier of scientific research (e.g., quantum science and single-molecule fluorescence) and practical applications (e.g., Lidar). However, there is a typical compromise between photon detection efficiency and jitter distribution. The light-trapping SPAD has been proposed to break this trade-off by coupling the vertically incoming photons into a laterally propagating mode while maintaining a small jitter and a thin Si device layer. In this work, we provide a 3D-based optical and electrical model based on practical fabrication conditions and discuss about design parameters, which include surface texturing, photon injection position, device area, and other features.

Applying the Darboux transformation in the optical-depth space allows building infinite chains of exact analytical solutions of the electromagnetic (EM) fields in planar 1D-graded dielectrics. As a matter of fact, infinite chains of solvable admittance profiles (e.g. refractive-index profiles, in the case of non-magnetic materials), together with the related EM fields are simultaneously and recursively obtained. The whole procedure has received the name “PROFIDT method” for PROperty and FIeld Darboux Transformation method. By repeating the Darboux transformations we can find out progressively more complex profiles and their EM solutions. An alternative is to stop after the first step and settle for a particular class of four-parameter admittance profiles that were dubbed of “sech(ξ)-type”. These profiles are highly flexible. For this reason, they can be used as elementary bricks for building and modeling profiles of arbitrary shape. In addition, the corresponding transfer matrix involves only elementary functions. The sub-class of “sech(ξ)-type” profiles with horizontal end-slopes (S-shaped function) is particularly interesting: these can be used for high-level modeling of piecewise-sigmoidal refractive-index profiles encountered in various photonic devices such as matchinglayers, antireflection layers, rugate filters, chirped mirrors and photonic crystals. These simple analytical tools also allow exploring the fascinating properties of a new kind of structure, namely smooth quasicrystals. They can also be applied to model propagation of other types of waves in graded media such as acoustic waves and electric waves in tapered transmission lines.

In this work, we first proposed a comprehensive numerical simulation for luminescent coupling efficiency (LCE) in a complete multi-junction (MJ) configuration and discussed its dependencies on temperature, incident light spectrum and bias voltage. We used finite difference time domain (FDTD) method and detailed balance principle to establish an optical transfer model. Based on that, we revealed the predominant influence factors of the simulation results in detail. This work will certainly fill a knowledge gap in understanding LCE and provide guidance to MJ photovoltaic device design and optimization as well.

We propose a rectangular resonator sensor structure with butterfly MMI coupler using SOI. It consists of the rectangular resonator, total internal reflection (TIR) mirror, and the butterfly MMI coupler. The rectangular resonator is expected to be used as bio and chemical sensors because of the advantages of using MMI coupler and the absence of bending loss unlike ring resonators. The butterfly MMI coupler can miniaturize the device compared to conventional MMI by using a linear butterfly shape instead of a square in the MMI part. The width, height, and slab height of the rib type waveguide are designed to be 1.5 μm, 1.5 μm, and 0.9 μm, respectively. This structure is designed as a single mode. When designing a TIR mirror, we considered the Goos-Hänchen shift and critical angle. We designed 3:1 MMI coupler because rectangular resonator has no bending loss. The width of MMI is designed to be 4.5 μm and we optimize the length of the butterfly MMI coupler using finite-difference time-domain (FDTD) method for higher Q-factor. It has the equal performance with conventional MMI even though the length is reduced by 1/3. As a result of the simulation, Qfactor of rectangular resonator can be obtained as 7381.

The Berreman matrix method has been previously used to model electromagnetic plane wave propagation through a hyperbolic metamaterial, and to determine transmission and reflection coefficients as a function of wavelength and varying angles of incidence. The Berreman matrix approach is now used to derive the propagation transfer function matrix in such materials. The eigenvalues of the Berreman matrix, which determine the transfer function, depend on the anisotropy. Beam propagation in such anisotropic materials are simulated using the transfer functions of all components of the electric (and magnetic) fields. Implications of this on negative refraction and the self-lensing of beams are explored.

The continuing controversy regarding the validity of assuming different photon lifetimes for counterpropagating modes in whistle-geometry ring resonators has led us to re-examine the commonly held view that coupling coefficients between any two ports in Y-junction couplers (regardless of their symmetry) do not depend on the direction of propagation. Rigorous three-dimensional finite-difference time-domain simulations show that the common assumptions about the operation o three-port couplers are sometimes grossly incorrect, as they arise from an oversimplified analytical model. An explanation is given why our results do not violate the Helmholtz reciprocity principle.

We demonstrate an efficient coupling of guided light of 1550 nm from a standard single-mode optical fiber to a silicon waveguide using the finite-difference time-domain method and propose a fabrication method of tapered optical fibers for efficient power transfer to silicon-based photonic integrated circuits. Adiabatically-varying fiber core diameters with a small tapering angle can be obtained using the tube etching method with hydrofluoric acid and standard single-mode fibers covered by plastic jackets. The optical power transmission of the fundamental HE11 and TE-like modes between the fiber tapers and the inversely-tapered silicon waveguides was calculated with the finite-difference time-domain method to be more than 99% at a wavelength of 1550 nm. The proposed method for adiabatic fiber tapering can be applied in quantum optics, silicon-based photonic integrated circuits, and nanophotonics. Furthermore, efficient coupling within the telecommunication C-band is a promising approach for quantum networks in the future.

The Building Block (BB) approach has recently emerged in photonic as a suitable strategy for the analysis and design of complex circuits. Each BB can be foundry related and contains a mathematical macro-model of its functionality. As well known, statistical variations in fabrication processes can have a strong effect on their functionality and ultimately affect the yield. In order to predict the statistical behavior of the circuit, proper analysis of the uncertainties effects is crucial. This paper presents a method to build a novel class of Stochastic Process Design Kits for the analysis of photonic circuits. The proposed design kits directly store the information on the stochastic behavior of each building block in the form of a generalized-polynomial-chaos-based augmented macro-model obtained by properly exploiting stochastic collocation and Galerkin methods. Using this approach, we demonstrate that the augmented macro-models of the BBs can be calculated once and stored in a BB (foundry dependent) library and then used for the analysis of any desired circuit. The main advantage of this approach, shown here for the first time in photonics, is that the stochastic moments of an arbitrary photonic circuit can be evaluated by a single simulation only, without the need for repeated simulations. The accuracy and the significant speed-up with respect to the classical Monte Carlo analysis are verified by means of classical photonic circuit example with multiple uncertain variables.

We propose adiabatic elimination (AE) to suppress the cross-talk in ultra-dense optical waveguides with sub-wavelength spacing. AE in atomic system is caused by a strong coupling nearby levels and a large detuning between them. Analogous to a three-level atomic system, in a set of three AE waveguides the outer waveguides function as an effective two-mode system like ground- and excited- states and the middle waveguide is same as dark state. While decomposition of three level system to two plus one has been reported previously, thanks to the “critical-point” three waveguides could be fully decomposed into three separate waveguides. Here we calculated the power profile using combination of three-dimensional (3D) finite difference time domain (FDTD) and 3D eigen-mode expansion method. At the input waveguide, initial amplitude of super-eigen-modes are obtained with 3D FDTD and the optical power in the three arms is then simulated with the overlap integral of the propagating super-eigen-modes with the fundamental transverse-electric (TE) of the isolated three waveguides. In the conventional coupled waveguides, sufficient inversion length at the telecommunication wavelength (1530 nm to 1565 nm) requires lambda spacing. Thanks to the critical point in our proposed waveguide, ultra-dense packaging with spacing as low as lambda/6, inversion length of several millimeters and cross-talk as low as 1 dB is obtained. Our preliminary experimental results are in good-agreement with the design. This concept can be extended to numerous number of optical waveguides. This AE waveguides will pave the way to ultra-dense multiplexing system as well as optical short-reach interconnects.

Relativistic Dirac and Weyl fermions were extensively studied in quantum field theory. Recently they emerged in the nonrelativistic condensed-matter setting as gapless quasiparticle states in some types of crystals. Notable examples of 2D systems include graphene and surface states in topological insulators such as Bi2Se3. Their 3D reincarnation is Dirac and Weyl semimetals that were recently discovered experimentally. Most of the research has been focused on their topological properties and electron transport. However, their optical and plasmonic properties are no less exciting. Optical phenomena can provide valuable insight into the fascinating physics of these materials. Moreover, their unique optical properties can be utilized in future optoelectronic devices. I will discuss several examples illustrating these points. They include plasmons and polaritons in Weyl semimetals, nonlinear optical response of graphene and topological insulators in the infrared and THz range, nonlinear generation of THz plasmons, and optical properties of chiral Dirac/Weyl fermions in a quantizing magnetic field.

Periodic arrays of proximate but noncontacting noble metal nanoparticles provide the ability to electromagnetically couple the surface plasmons on various nanoparticles to produce collective delocalized surface-plasmon-polariton modes with well characterized mode structure. Such structures provide intrinsic interest as well as provides an attractive concept for optical sensing in potentially open structures permitting gas or liquid to percolate through the structure. In this talk, I review our work on modeling the surface-plasmon-polariton modes of various nanoparticle arrays. I discuss one-dimensional chains and two-dimensional nanoparticle slabs. Ways of dealing with losses will be discussed. Provided the ratio of nanoparticle spacing to nanoparticle diameter (for spherical nanoparticles) exceeds a critical value, the electromagnetic interactions between nanoparticles are dominated by dynamic dipole-dipole coupling. In other words, one nanoparticle acts on the others (and on itself) by means of the retarded electromagnetic dipole-dipole interactions between all nanoparticles. The resulting collective modes delocalized over the structure are surface-plasmon polaritons. We consider various structures including infinite and finite chains, ring-shaped arrangements of nanoparticles, and two-dimensional slab arrays. Given the dispersion of surface-plasmon polaritons, we can then obtain the linear optical properties (e.g., reflection and transmission spectra, angle-dependence of reflectivity and transmittivity), which in turn provide important information on the design of nanoparticle-array-based devices. Surface-plasmon polaritons are strongly attenuated by homogeneous and inhomogenous broadening as well as by intrinsic radiative loss. We discuss strategies for mitigating these losses.

Classical electrodynamics and quantum mechanical models of quantum dots and molecules interacting with plasmonic systems are discussed. Calculations show that just one quantum dot interacting with a plasmonic system can lead to interesting optical effects, including optical transparencies and more general Fano resonance features that can be tailored with ultrafast laser pulses. Such effects can occur in the limit of moderate coupling between quantum dot and plasmonic system. The approach to the strong coupling regime is also discussed. In cases with two or more quantum dots within a plasmonic system, the possibility of quantum entanglement mediated through the dissipative plasmonic structure arises.

Optical polarization from AlGaN quantum well (QW) is crucial for realizing high-efficiency deep-ultraviolet (UV) light-emitting diodes (LEDs) because it determines the light emission patterns and light extraction mechanism of the devices. As the Al-content of AlGaN QW increases, the valence bands order changes and consequently the light polarization switches from transverse-electric (TE) to transverse-magnetic (TM) owing to the different sign and the value of the crystal field splitting energy between AlN (-169meV) and GaN (10meV). Several groups have reported that the ordering of the bands and the TE/TM crossover Al-content could be influenced by the strain state and the quantum confinement from the AlGaN QW system. In this work, we investigate the influence of QW thickness on the optical polarization switching point from AlGaN QW with AlN barriers by using 6-band k∙p model. The result presents a decreasing trend of the critical Al-content where the topmost valence band switches from heave hole (HH) to crystal field spilt-off (CH) with increasing QW thicknesses due to the internal electric field and the strain state from the AlGaN QW. Instead, the TE- and TM-polarized spontaneous emission rates switching Al-content rises first and falls later because of joint consequence of the band mixing effect and the Quantum Confined Stark Effect. The reported optical polarization from AlGaN QW emitters in the UV spectral range is assessed in this work and the tendency of the polarization switching point shows great consistency with the theoretical results, which deepens the understanding of the physics from AlGaN QW UV LEDs.

We present finite difference thermal modeling to predict temperature distribution, heat flux, and thermal resistance inside lasers with different waveguide geometries. We provide a quantitative experimental and theoretical comparison of the thermal behavior of shallow-ridge (SR) and buried-heterostructure (BH) lasers. We investigate the influence of a split heat source to describe p-layer Joule heating and nonradiative energy loss in the active layer and the heat-sinking from top as well as bottom when quantifying thermal impedance. From both measured values and numerical modeling we can quantify the thermal resistance for BH lasers and SR lasers, showing an improved thermal performance from 50K/W to 30K/W for otherwise equivalent BH laser designs.

The effect of current spreading on the lateral far–field divergence of high–power broad–area lasers is investigated with a time–dependent model using different descriptions for the injection of carriers into the active region. Most simulation tools simply assume a spatially constant injection current density below the contact stripe and a vanishing current density beside. Within the drift–diffusion approach, however, the injected current density is obtained from the gradient of the quasi–Fermi potential of the holes, which solves a Laplace equation in the p–doped region if recombination is neglected. We compare an approximate solution of the Laplace equation with the exact solution and show that for the exact solution the highest far–field divergence is obtained. We conclude that an advanced modeling of the profiles of the injection current densities is necessary for a correct description of far–field blooming in broad–area lasers.

Military requirements demand both single and dual-color infrared (IR) imaging systems with both high resolution and sharp contrast. To quantify the performance of these imaging systems, a key measure of performance, the modulation transfer function (MTF), describes how well an optical system reproduces an objects contrast in the image plane at different spatial frequencies. At the center of an IR imaging system is the focal plane array (FPA). IR FPAs are hybrid structures consisting of a semiconductor detector pixel array, typically fabricated from HgCdTe, InGaAs or III-V superlattice materials, hybridized with heat/pressure to a silicon read-out integrated circuit (ROIC) with indium bumps on each pixel providing the mechanical and electrical connection. Due to the growing sophistication of the pixel arrays in these FPAs, sophisticated modeling techniques are required to predict, understand, and benchmark the pixel array MTF that contributes to the total imaging system MTF. To model the pixel array MTF, computationally exhaustive 2D and 3D numerical simulation approaches are required to correctly account for complex architectures and effects such as lateral diffusion from the pixel corners. It is paramount to accurately model the lateral di_usion (pixel crosstalk) as it can become the dominant mechanism limiting the detector MTF if not properly mitigated. Once the detector MTF has been simulated, it is directly decomposed into its constituent contributions to reveal exactly what is limiting the total detector MTF, providing a path for optimization. An overview of the MTF will be given and the simulation approach will be discussed in detail, along with how different simulation parameters effect the MTF calculation. Finally, MTF optimization strategies (crosstalk mitigation) will be discussed.

We have developed ultra-low noise quadrant InGaAs photoreceivers for multiple applications ranging from Laser Interferometric Gravitional Wave Detection, to 3D Wind Profiling. Devices with diameters of 0.5 mm, 1mm, and 2 mm were processed, with the nominal capacitance of a single quadrant of a 1 mm quad photodiode being 2.5 pF. The 1 mm diameter InGaAs quad photoreceivers, using a low-noise, bipolar-input OpAmp circuitry exhibit an equivalent input noise per quadrant of <1.7 pA/√Hz in 2 to 20 MHz frequency range. The InGaAs Quad Photoreceivers have undergone the following reliability tests: 30 MeV Proton Radiation up to a Total Ionizing Dose (TID) of 50 krad, Mechanical Shock, and Sinusoidal Vibration.

PureB silicon photodiodes have nm-shallow p+n junctions with which photons/electrons with penetration-depths of a few nanometer can be detected. PureB Single-Photon Avalanche Diodes (SPADs) were fabricated and analysed by 2D numerical modeling as an extension to TCAD software. The very shallow p+ -anode has high perimeter curvature that enhances the electric field. In SPADs, noise is quantified by the dark count rate (DCR) that is a measure for the number of false counts triggered by unwanted processes in the non-illuminated device. Just like for desired events, the probability a dark count increases with increasing electric field and the perimeter conditions are critical. In this work, the DCR was studied by two 2D methods of analysis: the “quasi-2D” (Q-2D) method where vertical 1D cross-sections were assumed for calculating the electron/hole avalanche-probabilities, and the “ionization-integral 2D” (II-2D) method where crosssections were placed where the maximum ionization-integrals were calculated. The Q-2D method gave satisfactory results in structures where the peripheral regions had a small contribution to the DCR, such as in devices with conventional deepjunction guard rings (GRs). Otherwise, the II-2D method proved to be much more precise. The results show that the DCR simulation methods are useful for optimizing the compromise between fill-factor and p-/n-doping profile design in SPAD devices. For the experimentally investigated PureB SPADs, excellent agreement of the measured and simulated DCR was achieved. This shows that although an implicit GR is attractively compact, the very shallow pn-junction gives a risk of having such a low breakdown voltage at the perimeter that the DCR of the device may be negatively impacted.

The conventional phenomenological approach describes the response time of semiconductor photodiodes to short laser pulses as time required for collection of non-equilibrium carriers via processes of drift and diffusion. The effect of displacement currents due to dielectric relaxation of majority carriers in the charge-neutral region of semiconductor photodiode is usually neglected. This paper shows that dielectric relaxation of majority carriers may dominate the slow response of not fully depleted photodiodes and has to be taken into account for correct analysis of silicon photodiode response to a brief laser pulse. A phenomenological expression for the photodiode response time that accounts for the displacement current effects is proposed and used to compare with experimental results.

In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the quantum efficiency in the conventional photodetectors is overcome. In RCE-PDs, large bandwidth can be achieved using a thin absorption layer while the use of a resonant cavity allows for multiple passes of light in the absorption which boosts the quantum efficiency. In this paper, a complete bias-dependent model for the Resonant Cavity Enhanced-Separated Absorption Graded Charge Multiplication-Avalanche Photodetector (RCE-SAGCM-APD) is presented. The proposed model takes into account the case of drift velocities other than the saturation velocity, thus modeling this effect on the photodetector different design parameters such as Gain, Bandwidth and Gain-Bandwidth product.

In nitride ternary alloys, natural compositional disorder induces strong electronic localization effects. We present a new experimental approach which allows a direct probing at nanometer scale of disorder-induced localization effects in InGaN/GaN quantum wells (QWs). In this experiment, samples are p-type heterostructures incorporating an InGaN/GaN QW nearby the surface. The electrons are locally injected from a scanning tunneling microscope (STM) tip into the conduction band of the thin cladding top GaN layer and captured in the InGaN QW where they radiatively recombine. The injected current is maintained constant by the STM feedback loop and the injection electron energy is controlled by the bias voltage applied to the tip-sample tunnel junction. The luminescence onset voltage coincides with electron injection above the bottom of the conduction band in the bulk GaN (beyond the band bending region). Thereby, scanning the tip allows the high-resolution mapping of the luminescence process in the InGaN QW. Spatial fluctuations of the luminescence peak energy and linewidth are observed on the scale of a few nanometers, which are characteristic of disorder-induced carrier localization. A model based on the so-called localization landscape theory is developed to take into account the effect of alloy disorder into simulations of the structure properties. The localization landscape notably describes an effective confining potential, whose basins and crests define the localization regions of carriers. This theory accounts well for the observed nanometer scale carrier localization and the energy-dependent luminescence linewidth observed for the quantum electron states in the disordered energy band.

As doping material rare-earth elements are widely used changing considerably semiconductor’s optical, electrical and radiative properties. This work describes influence of the gadolinium on radiative and optical properties of the ZnSe. Single crystals were grown by physical transport method and were doped during growth. GdSe compound were doping source. X-ray diffraction, photoluminescent properties and optical transmission in the wide spectral range were analyzed. Radiative bands corresponded to intracentered transition of the doping impurity have not been registered. Gadolinium ions contribute to the background impurity activation creating radiative transitions from conduction band to the Cu2+ levels and intracentered transitions of the Cr2+ ions. However, edge band intensity has strong dependence from impurity concentration and is very less to the intensity of the undoped ZnSe. Edge band decay changes from bimolecular to the monomolecular recombination. Optical transparency is decreasing, but fundamental absorption band position is stable. X-ray diffraction shows that single crystals have zinc blende crystal structure and there is no GdSe phase formation. However, crystalline grain calculus reveals its growth with the impurity increase. Weak shift of the peak direction (331) is detected, while peaks directions (311) and (111) are stable. Hence, complex analysis of the ZnSe:Gd has determined that the Gd impurity is present in the single crystals and creates associates. Composition of these associates could be background impurities copper and chromium, which activates with crystal’s free energy captured by gadolinium ions.

The absorption of type-II nanostructures is often weaker than type-I counterpart due to spatially separated electrons and holes. We model the bound-to-continuum absorption of type-II quantum rings (QRs) using a multiband source-radiation approach using the retarded Green function in the cylindrical coordinate system. The selection rules due to the circular symmetry for allowed transitions of absorption are utilized. The bound-tocontinuum absorptions of type-II GaSb coupled and uncoupled QRs embedded in GaAs matrix are compared here. The GaSb QRs act as energy barriers for electrons but potential wells for holes. For the coupled QR structure, the region sandwiched between two QRs forms a potential reservoir of quasi-bound electrons. Electrons in these states, though look like bound ones, would ultimately tunnel out of the reservoir through barriers. Multiband perfectly-matched layers are introduced to model the tunneling of quasi-bound states into open space. Resonance peaks are observed on the absorption spectra of type-II coupled QRs due to the formation of quasi-bound states in conduction bands, but no resonance exist in the uncoupled QR. The tunneling time of these metastable states can be extracted from the resonance and is in the order of ten femtoseconds. Absorption of coupled QRs is significantly enhanced as compared to that of uncoupled ones in certain spectral windows of interest. These features may improve the performance of photon detectors and photovoltaic devices based on type-II semiconductor nanostructures.

Optical filters are required to have narrow band-pass filtering in the spectral C-band for applications such as signal tracking, sub-band filtering or noise suppression. These requirements lead to a variety of filters such as Mach-Zehnder interferometer inter-leaver in silica, which offer thermo-optic effect for optical switching, however, without proper thermal and optical efficiency. In this paper we propose tunable thermo-optic filtering device based on coated silicon slab resonator with increased Q-factor for the C-band optical switching. The device can be designed either for long range wavelength tuning of for short range with increased wavelength resolution. Theoretical examination of the thermal parameters affecting the filtering process is shown together with experimental results. Proper channel isolation with an extinction ratio of 20dBs is achieved with spectral bandpass width of 0.07nm.

A code is said to be an error-correcting, if the correct code word can always be deducted from an erroneous word. Hamming code is most suitable for error detection and correction for digital data. It facilitate error detection and correction in code information. Here 7 bit Hamming code convertor is proposed. In this code, to each group of m information bits, n parity checking bits are located at positions 2^(n-1) from left are added to form an (m+n)-bit code word. Code convertor device is designed using Mach-Zehnder interferometer (MZI). MZI is an optical switch, able to transfer signal from one port to other.

Not so long ago, pseudo random numbers generated by numerical formulae were considered to be adequate for encrypting important data-files, because of the time needed to decode them. With today’s ultra high-speed processors, however, this is no longer true. So, in order to thwart ever-more advanced attempts to breach our system’s protections, cryptologists have devised a method that is considered to be virtually impossible to decode, and uses what is a limitless number of physical random numbers. This research describes a method, whereby laser diode’s frequency noise generate a large quantities of physical random numbers. Using two types of photo detectors (APD and PIN-PD), we tested the abilities of two types of lasers (FP-LD and VCSEL) to generate random numbers. In all instances, an etalon served as frequency discriminator, the examination pass rates were determined using NIST FIPS140-2 test at each bit, and the Random Number Generation (RNG) speed was noted.

Thermal poling, a technique to create permanently effective second-order susceptibility in silica optical fibers, has a wide range of applications, such as frequency conversion, electro-optic modulation, switching and polarization-entangled photon pairs generation. After many works where a conventional configuration anode-cathode was used, in 2009 a new electrode configuration (double-anode) was adopted, which allows for a more temperature-stable depletion region formation and a higher value of effective Chi2^{1, 2}. In this work we demonstrate, via numerical simulations realized in COMSOL® Multiphysics, that in a double-anode configuration the effective value of Chi2 strongly depends on the relative position of the core with respect to the electrodes, requiring an accurate and precisely tailored geometry of the fiber, while in a single-anode configuration this value, for standard poling conditions¹ is almost independent of the position of the core, offering the possibility of relaxing the manufacturing constraint of the fiber fabrication. We also demonstrate that, in the same experimental conditions, the maximum value of effective Chi2 induced by thermal poling in double-anode configuration is smaller than the one obtained in single-anode configuration for any position of the core in the range between the anodic surface and the geometric center of the fiber. Finally, we report the experimental observation of depletion region formation in a twin-hole fused silica fiber poled in single-anode configuration. Using a QPM SHG experimental set-up, we demonstrate that the value of Chi2 obtained in the single anode configuration is at least as large as for the double anode one.

In recent years, food safety issues caused by contamination of chemical substances or microbial species have raised a major area of concern to mankind. The conventional chromatography-based methods for detection of chemical are based on human-observation and slow for real-time monitoring. The surface plasmon resonance (SPR) sensors offers the capability of detection of very low concentrations of adulterated chemical and biological agents for real-time by monitoring. Thus, adulterant agent in food gives change in refractive index of pure food result in corresponding phase change. These changes can be detected at the output and can be related to the concentration of the chemical species present at the point.

The signal-to-noise ratio (SNR) of filtered incoherent light can be approximated from the product of the coherence time of the light and the equivalent (electrical) noise bandwidth of the detector. This approximation holds only for the light with very short coherence time, that is in the case where the optical bandwidth of the light is much larger than the electrical bandwidth. We present here an expression for accurate evaluation of the SNR of the filtered incoherent light, which computes SNR from arbitrary shapes of optical and electrical filter power spectral densities (PSD). The PSDs of the filters can be measured using optical and electrical spectrum analyzers. Using our expression, we show that the SNR reaches unity when the electrical filter bandwidth is becoming larger than the optical filter bandwidth. To prove the theory, we evaluate and directly measure SNR of an incoherent light source filtered with several optical filters with bandwidths larger and commensurate with the bandwidth of the detector. For later we used optical and electrical filters with 3-dB bandwidths of 15 GHz and 10 GHz, respectively. Using our expression to evaluate SNR we obtained results in a good agreement with directly measured SNR. The results also prove that the approximation for evaluating SNR does not provide accurate results. The PSD of the detector with large noise bandwidth is difficult to measure using spectrum analyzer. There- fore, we report here a method for measuring the electrical noise bandwidth of the detector using the heterodyne linewidth measurement technique with tunable laser.

An optical modulator based on the racetrack resonator configuration is introduced. The structure of the resonator modulator is built from silicon nanowires on silica. The cladding and voids between the silicon nanowires are filled with an electro-optic polymer. The proposed modulator is fully CMOS compatible. When the resonance is tuned to the 1.55μm wavelength, it experiences a wavelength shift upon voltage application, which is measured at the output as a change in the power level.

In this paper, we propose an efficient approach to solve the BPM equation. By splitting the complex field into real and imaginary parts, the method is proved to be at least 30% faster than the conventional BPM. This method was tested on several optical components to test the accuracy.

High performance optical structures based on new platform for the design of photonic structures are proposed in this work. The platform is previously proposed and is based on the design of an ultra thin waveguide with narrow lateral thickness with low confined field inside the core waveguide which enables using this waveguide for building high performance photonic based sensors and modulators. An MZI based modulator is reported with extinction ratio of 20.36 dB. These values resulted in high performance photonic structures as compared to the conventional waveguide based structures delimiting some of the constraints when using photonic structures. Keywords: interference, modulation, sensing, photonic structures, Mach-Zehnder

The ease of fabrication and compactness of devices based on tapered optical fibers contribute to its potential using in several applications ranging from telecommunication components to sensing devices. In this work, we proposed, fabricated, and characterized a spectral filter made of biconical taper from a coaxial optical fiber. This filter is defined by adiabatically tapering a depressed-cladding fiber. The adiabatic taper profile obtained during fabrication prevents the interference of other modes than HE₁₁ and HE₁₂ ones, which play the main role for the beating phenomenon and the filter response. The evolution of the fiber shapes during the pulling was modeled by two coupled partial differential equations, which relate the normalized cross-section area, and the axial velocity of the fiber elongation. These equations govern the mass and axial momentum conservation. The numerical results of the filter characteristics are in good accordance with the experimental ones. The filter was packaged in order to let it ready for using in optical communication bands. The characteristics are: free spectral range (FSR) of 6.19 nm, insertion loss bellow 0.5 dB, and isolation > 20 dB at C-band. Its transmission spectrum extends from 1200 to 1600 nm where the optical fiber core supports monomode transmission. Such characteristics may also be interesting to be applied in sensing applications. We show preliminary numerical results assuming a biconic taper embedded into a dielectric media, showing promising results for electro-optic sensing applications.

Recently, non-circular microresonators have been studied mainly due to their ability to provide long interaction length and ease the air-gap spacing tolerance. The use of rectangular, square-shaped, and/ or polygonal optical microresonators with sharp corners can be limited by severe energy loss at the corners. By incorporating optimum fillet (rounding of corners) design at sharp corners of such optical microresonators optical loss can be eliminated at sharp corners. This results in significantly increasing the quality factor of the round-cornered square-shaped microresonators in comparison to the conventional circular-ring resonator systems. The enhanced quality factor makes the microresonator a promising system that can be used in advanced measurement and detection applications. The two dimensional finite element analysis of the electromagnetic frequency presented in this study quantifies the effect of rotation of round-cornered square-shaped resonators about the coupling region on the quality factor of single-mode resonances in a add-drop configuration system. It is found that the quality factor of these resonators steadily increases with the rotation (0-45° angle) of resonator about the coupling point.

The Group IV Photonics (GFP) which include an alloy of Si, Ge & Sn that gives a direct bandgap material (GeSn, SiGeSn) in near and mid-IR region used as an active material in photonics devices. The multiple quantum well SiGeSn/GeSn transistor laser structure is considered in this paper and performance parameters are evaluated for the same. The result shows that the threshold base current density (2.6 kA/cm²) for the proposed device initially decreases with increasing number of quantum well (QW) and later on it saturates. The current gain and output photon density of the device decreases and increases respectively, with increasing number of QW.

A non-mechanical refractive laser beam steering device has been developed to provide continuous, two-dimensional steering of infrared beams. The technology implements a dielectric slab waveguide architecture with a liquid crystal (LC) cladding. With voltage control, the birefringence of the LC can be leveraged to tune the effective index of the waveguide under an electrode. With a clever prism electrode design a beam coupled into the waveguide can be deflected continuously in two dimensions as it is coupled out into free space. The optical interaction with LC in this beamsteerer is unique from typical LC applications: only the thin layer of LC (100s of nm) near the alignment interface interacts with the beam’s evanescent field. Whereas most LC interactions take place over short path lengths (microns) in the bulk of the material, here we can interrogate the behavior of LC near the alignment interface over long path lengths (centimeters). In this work the beamsteerer is leveraged as a tool to study the behavior of LC near the alignment layer in contrast to the bulk material. We find that scattering is substantially decreased near the alignment interface due to the influence of the surface anchoring energy to suppress thermal fluctuations. By tracking the position of the deflected beam with a high speed camera, we measure response times of the LC near the interface in off-to-on switching (~ms) and on-to-off switching (~100ms). Combined, this work will provide a path for improved alignment techniques, greater optical throughput, and faster response times in this unique approach to non-mechanical beamsteering.

The large majority of surface plasmon resonance based devices use noble metals, namely gold or silver, in their manufacturing process. These metals present low resistivity, which leads to low optical losses in the visible and near infrared spectrum ranges. Gold shows high environmental stability, which is essential for long-term operation, and silver’s lower stability can be overcome through the deposition of an alumina layer, for instance. However, their high cost is a limiting factor if the intended target is large scale manufacturing.

In this work, it is considered a cost-effective approach through the selection of aluminum as the plasmonic material and hydrogenated amorphous silicon instead of its crystalline counterpart. This surface plasmon resonance device relies on Fano resonance to improve its response to refractive index deviations of the surrounding environment. Fano resonance is highly sensitive to slight changes of the medium, hence the reason we incorporated this interference phenomenon in the proposed device.

We report the results obtained when conducting Finite-Difference Time Domain algorithm based simulations on this metal-dielectric-metal structure when the active metal is aluminum, gold and silver. Then, we evaluate their sensitivity, detection accuracy and resolution, and the obtained results for our proposed device show good linearity and similar parameter performance as the ones obtained when using gold or silver as plasmonic materials.

Most modern systems of the optical image registration are based on the matrices of photosensitive semiconductor heterostructures. However, measurement of radiation intensities up to several MW/cm² -level using such detectors is a great challenge because semiconductor elements have low optical damage threshold. Reflecting or absorbing filters that can be used for attenuation of radiation intensity, as a rule, distort beam profile. Furthermore, semiconductor based devices have relatively narrow measurement wavelength bandwidth.

We introduce a novel matrix method of optical image registration. This approach doesn’t require any attenuation when measuring high radiation intensities. A sensitive element is the matrix made of thin transparent piezoelectric crystals that absorb just a small part of incident optical power. Each crystal element has its own set of intrinsic (acoustic) vibration modes. These modes can be exited due to the inverse piezoelectric effect when the external electric field is applied to the crystal sample providing that the field frequency corresponds to one of the vibration mode frequencies. Such piezoelectric resonances (PR) can be observed by measuring the radiofrequency response spectrum of the crystal placed between the capacitor plates. PR frequencies strongly depend on the crystal temperature. Temperature calibration of PR frequencies is conducted in the uniform heating conditions. In the case a crystal matrix is exposed to the laser radiation the incident power can be obtained separately for each crystal element by measuring its PR frequency kinetics providing that the optical absorption coefficient is known. The operating wavelength range of such sensor is restricted by the transmission bandwidth of the applied crystals.

A plane matrix constituting of LiNbO₃ crystals was assembled in order to demonstrate the possibility of application of the proposed approach. The crystal elements were placed between two electrodes forming a capacitor which was interconnected to the lock-in detection system. The radiofrequency response to the applied voltage from the generator was measured simultaneously for all elements.

In this paper, we analyze the influence of the crosstalk level and the dynamic range on the basic characteristics of a silicon solid-state photomultiplier and demonstrate their importance for detecting of optical signals with backlight illumination, in particular, for LIDAR application. Experimental results obtained in the study of threshold and fluctuation parameters of detectors with different levels of crosstalk and dynamic range are presented. It is shown that the detector design combining a high dynamic range with a small crosstalk gives a noticeable advantage in such applications.

We analyze the characteristics of plasmonics-based enhancement of a wire-grid polarizer (WGP) by rigorous coupledwave analysis (RCWA). We consider blazed WGP (bWGP) for improvement of polarimetric performance based on plasmonic momentum-matching in the metal/dielectric interface. The analysis used a model of triangular wire-grids approximated with five graded layers of identical thickness. We have compared the performance to that of a conventional WGP (cWGP) with a corresponding lamellar grating shape profile. As a performance measure, we calculated transmittance (TR) and extinction ratio (ER). It was found that TR in both cases tends to decrease monotonically with a longer period (Λ). The maximum TR of bWGPs is lower than cWGPs. On the other hand, maximum ER of bWGPs is much higher than that of cWGPs, particularly at a longer period, with an extinction peak peaked at Λ = 800 nm. For cWGPs, an extinction peak is observed at Λ = 200 nm with comparable enhancement (~42 dB). We have also computed relative TR (RTR) and relative ER (RER) for assessment of performance relative to cWGP. RTR decreases slowly in a manner similar to TR, however, RER increases exponentially with a longer wire-grid period. The results suggest that strong localization of near-fields observed with bWGPs can be used to improve polarimetric performance of a WGP.

Raman spectroscopy is commonly used in chemistry and biology. As vibrational information is specific to the chemical bonds, Raman spectroscopy provides fingerprints to identify the type of molecules in the sample. In this paper, we simulate the Raman spectrum of organic and inorganic materials by GAMESS and GAUSSIAN on our high- performance cluster. By using MPI (message passing interface), we are able to run the codes in parallel. From our simulations, we will set up a database that allows search algorithms to quickly identify N-H and O-H bonds in different materials.

Coupled Mode theory and Variational methods are the most extensively used analytical methods for the study of coupled optical waveguides. In this paper we have discussed a variation of the Ritz Galerkin Variational method (RGVM) wherein the trial field is a superposition of an orthogonal basis set which in turn is generated from superposition of the individual waveguide modal fields using Gram Schmidt Orthogonalization Procedure (GSOP). The conventional coupled mode theory (CCMT), a modified coupled mode theory (MCMT) incorporating interaction terms that are neglected in CCMT, and an RGVM using orthogonal basis set (RG-GSOP) are compared for waveguide arrays of different materials. The exact effective indices values for these planar waveguide arrays are also studied. The different materials have their index-contrasts ranging between the GaAs/ AlGaAs system to Si/SiO2 system. It has been shown that the error in the effective indices values obtained from MCMT and CCMT is higher than RGVM-GSOP especially in the case of higher index-contrast. Therefore, for accurate calculations of the modal characteristics of planar waveguide arrays, even at higher index-contrasts, RGVM-GSOP is the best choice. Moreover, we obtain obviously orthogonal supermode fields and Hermitian matrix from RGVM-GSOP.

We use a coaxial fiber, which is a cylindrical coupled waveguide structure consisting of two concentric cores, the inner rod and an outer ring core as a first order dispersive media to achieve temporal Talbot effect for pulse repetition rate multiplication (PRRM) in high bit rate optical fiber communication. It is observed that for an input Gaussian pulse train with pulse width, 2τ0=1ps at a repetition rate of 40 Gbps (repetition period, T=25ps), an output repetition rate of 640 Gbps can be achieved without significant distortion at a length of 40.92 m.

In this work we report the modelling of the emissivity of micromachined black silicon structure based on treating the black silicon as an array of cone-shaped textured silicon structure. The geometrical ray optics is used to calculate the reflection and transmission coefficient for each ray hitting the silicon surface with a certain incidence angle. The coherence length is assumed to be much smaller than the travelled distance by the rays such that their contribution is summed incoherently. The validity of the geometrical optics holds since the modeled structure dimensions are much larger than the wavelength. The model is applied on experimental data reported in the literature for black silicon structure fabricated using femtosecond laser pulses. The height of the structure is in the order of 20 μm, the cone angle is about 20 degrees and silicon doping level is about 10¹⁹ cm^-3. The model results are compared to the measured emissivity in the wavelength range of 500 nm to 2000 nm good matching within 0.5 % to 5 % is obtained for smaller to longer wavelengths, respectively.