This PDF file contains the front matter associated with SPIE Proceedings Volume 8988 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

In this paper, we demonstrate recent progress in graphene-based photonic waveguide devices such as polymer waveguide polarizer, thermo-optic mode extinction modulator and plasmonic photodetector for graphene-based photonic integrated circuits.

Electro-optical printed circuit board technology (EOCB) based on integrated planar polymer optical waveguides has been the subject of research and development for many years to provide a cost viable, fully integrated system embedded optical interconnect solution, however a number of constraints of this technology have yet to be overcome. Optical coupling loss at the input and output of the waveguides is one of the major issues and waveguide end facet roughness is one of the main sources of the coupling loss which is investigated in this paper. The results of a comprehensive investigation of the end facet roughness of multimode polymer waveguides, fabricated on FR4 printed circuit boards, PCBs, and its effect of optical loss are presented theoretically and experimentally. The waveguide end facet roughness was measured using an atomic force microscope, AFM, when the waveguides were cut using a milling router with various numbers of cutting edges called flutes. The optimized cutting parameters are derived and the optical coupling loss, between the laser source and the waveguide, due to the different roughness magnitudes is measured by experiment for the first time. To improve the surface quality and decrease the waveguide optical loss, a new fabrication technique for reducing the end facet roughness after cutting is proposed and demonstrated. The insertion loss was reduced by 2.60 dB ± 1.3 dB which is more than that achieved by other conventional methods such as index matching fluid.

Photonic integrated circuits based on III-V semiconductor polarization-maintaining waveguides were designed and fabricated for the first time for application in a compact cold-atom gravimeter^1,2 at an operational wavelength of 780 nm. Compared with optical fiber-based components, semiconductor waveguides achieve very compact guiding of optical signals for both passive functions, such as splitting and recombining, and for active functions, such as switching or modulation. Quantum sensors, which have enhanced sensitivity to a physical parameter as a result of their quantum nature, can be made from quantum gases of ultra-cold atoms. A cloud of ultra-cold atoms may start to exhibit quantum-mechanical properties when it is trapped and cooled using laser cooling in a magneto-optical trap, to reach milli-Kelvin temperatures. The work presented here focuses on the design and fabrication of optical devices for a quantum sensor to measure the acceleration of gravity precisely and accurately. In this case the cloud of ultra-cold atoms consists of rubidium (⁸⁷Rb) atoms and the sensor exploits the hyperfine structure of the D1 transition, from an outer electronic state of 5 ²S _½ to 5 ²P_3/2 which has an energy of 1.589 eV or 780.241 nm. The short wavelength of operation of the devices dictated stringent requirements on the Molecular Beam Epitaxy (MBE) and device fabrication in terms of anisotropy and smoothness of plasma etch processes, cross-wafer uniformities and alignment tolerances. Initial measurements of the optical loss of the polarization-maintaining waveguide, assuming Fresnel reflection losses only at the facets, suggested a loss of 8 dB cm^-1, a loss coefficient, α, of 1.9 (±0.3) cm^-1.

High-index-contrast optical devices form the backbone of densely integrated photonic circuits. While these devices are traditionally fabricated using lithography and etching, their performance is often limited by defects and sidewall roughness arising from fabrication imperfections. This paper reports a versatile, roll-to-roll and backend compatible technique for the fabrication of high-performance, high-index-contrast photonic structures in composition-engineered chalcogenide glass (ChG) thin films. Thin film ChG have emerged as important materials for photonic applications due to their high refractive index, excellent transparency in the infrared and large Kerr non-linearity. Both thermally evaporated and solution processed As-Se thin films are successfully employed to imprint waveguides and micro-ring resonators with high replicability and low surface roughness (0.9 nm). The micro-ring resonators exhibit an ultra-high quality-factor of 4 × 10⁵ near 1550 nm wavelength, which represents the highest value reported in ChG micro-ring resonators. Furthermore, sub-micron nanoimprint of ChG films on non-planar plastic substrates is demonstrated, which establishes the method as a facile route for monolithic fabrication of high-index-contrast devices on a wide array of unconventional substrates.

Complex interconnection patterns in electrical PCBs have to use multiple layers of copper tracks. However, the same interconnections can be made in a single layer using optical waveguides as they cross on the same layer. Waveguide crossings where two waveguides intersect in the same optical layer are particularly important components as they offer OPCB layout designers additional flexibility to solve layout problems such as routing around cutout areas, electrical components and other obstacles on an OPCB. Use of waveguide crossings can also help to avoid sharp bends in the design as these bends are an important cause of optical loss. Despite all of the advantages of waveguide crossings, and although most of the light travels along the intended waveguide, a proportion of the optical power in one waveguide will couple into the crossing waveguide at each intersection point or couple out of the original waveguide and into the cladding. This coupling phenomenon causes optical loss and crosstalk in the system. In this paper, the results of an investigation of the optical loss due to the crossing of multimode polymer waveguide, fabricated on FR4 printed circuit boards, PCBs, as a function of crossing angles are presented theoretically and experimentally. The results from ray tracing simulation is compared with the experiment results and the contrast is discussed.

A detailed study of the fabrication and continuous-wave laser operation of Ti:sapphire channel waveguides written with femtosecond (fs) and picosecond (ps) laser pulses in the bulk of a Ti:sapphire crystal is presented. The waveguides were produced using the double-line approach and the effect of parameters such as the laser pulse duration, repetition rate and interline spacing were investigated for optimizing the laser operation. Structures fabricated by fs-laser pulses (180 fs) exhibited superior performance delivering output powers up 143 mW with a slope efficiency of 23.5% and producing laser emission above a threshold of 84 mW. The emission wavelength was tuned over a wavelength range spanning from 700 to 920 nm using cavity optics with broadband transmission at the lasing wavelength in combination with a birefringent filter in an external cavity.

Tellurite waveguides are promising candidates for high gain with broad-bandwidth, especially with Er-doping, which covers the telecommunications band and important spectral absorption features of atmospheric CO2. This study aimed at developing new Er,Yb-doped tellurite waveguide power amplifier modules suited to LIDAR measurements from space that will enable improved mapping of the concentration and distribution of CO2 in our atmosphere. A comparison of the optical properties of bulk and waveguide samples has been made, with double-clad waveguide devices, suited for high power diode pumping, currently under test.

Pulsed sources based on approaches that employ only photonic components and no RF components will be discussed in this talk. Several technologies have been explored to generate actively mode-locked sources using electronically driven fiber ring cavities. However, for these sources the pulse repetition rate is usually limited by the bandwidth of the intracavity modulator. Filtering of highly-stable low repetition rate optical combs utilizing cavities such as Fabry-Perot etalons can be used to overcome this limitation. This scheme is not flexible as it requires highly precise control of ultrahigh finesse etalons which limits the repetition rate to the free spectral range of the filter. Pulsed sources based on semiconductor devices offer many advantages, including large gain bandwidth, rapid tunability, long-term stability. In this work we introduce a novel, simple method to generate optical clock with wavelength tunability using two continuous wave (CW) lasers. The lasers are injected into a conventional SOAs-based fiber ring laser. The beating signal generated by these two lasers causes the modulation of the SOA gain saturation inside the cavity. Thus, the SOA provides gain and functions as the modulator as well as the gain medium. When the lasing mode inside the cavity is amplified, it also results in gain-induced four wave mixing. The proposed technique is particularly versatile, overcoming the bandwidth limitation of other techniques, which require RF sources. Moreover, this technique provides the possibility for hybrid integration as it is comprised of semiconductor chips that can be heterogeneously integrated on a Si platform.

The nonreciprocal phase shift caused by the first-order magneto-optical effect is effective in realizing optical nonreciprocal devices such as optical isolators and circulators in silicon waveguide platforms. The low refractive index of the buried oxide layer in a Silicon-On-Insulator (SOI) waveguide enhances the magneto-optical phase shift, which reduces the device footprints. In order to obtain the magneto-optical phase shift, it is required to integrate a magnetooptical material on the silicon waveguide. A surface activated direct bonding technique was developed to integrate a magneto-optical garnet single crystal on the silicon waveguides. Using this technique, a silicon waveguide optical isolator based on the magneto-optical phase shift was demonstrated with an optical isolation of 30 dB at a wavelength of 1548 nm. Furthermore, a four port optical circulator was demonstrated with maximum isolations of 33.5 and 29.1 dB in cross and bar ports, respectively, at a wavelength of 1543 nm. Excess insertion losses were 13 and 12.5 dB in the isolator and circulator, respectively.

Femtosecond laser direct writing (FLDW) is developing rapidly but to date, there is no native optical isolator (needed to mitigate reflections in any optical system) for the platform. As a step towards integrated glass isolators, we have investigated FLDW in kHz and MHz pulse rate regimes for two magneto-optical glasses (TG20 and MR3-2) to ultimately create one-way structures based on the Faraday effect. Previously, we fabricated basic waveguides obtaining single-mode guidance at 632 nm (the Faraday effect is strongest near the Tb³⁺ resonance at 485 nm) in both regimes. kHz regime waveguides were isotropic but had high propagation loss due to associated photodarkening (which could be post-annealed). The propagation loss of the MHz regime waveguides was acceptable due to lower photodarkening, but the waveguides were too narrow to confine light properly because of the very strong focus of the writing beam. To try to combine the lower loss with larger waveguide width, we created overlapping structures using a series of superposed waveguides arranged in rings in MHz regime. The confinement in these multi-ring structures was indeed improved and the structure propagation loss was intermediate between that of one-path waveguides created in kHz and MHz regimes. For most other glasses, MHz FLDW systems operate in a heat-accumulation regime, producing waveguide diameters much larger than the writing laser spot size and superposed waveguides that merge into one by melting. Here, the sub-unit waveguides maintained their individual identity indicating that the heat-accumulation effect was absent.

In this paper we analyze the optical and transversal magnetooptical (MO) response of magnetoplasmonic (MP) nanostructures. The MP structure is a 1D periodic gold grating fabricated by lift-off technique on the MO dielectric substrate (Bi-substituted yttrium iron garnet Bi_xY_3−xFe₅O₁₂). Following our recent theoretical work (Opt. Express 21, pp. 2174121755, Sep 2013.), we confirm here experimentally the predicted dependence of the MO response on the geometry of the grating, that is directly attributed to the anticrossing behavior of the Fabry-Perot (FP) resonance in the grating’s slits and the surface plasmon resonances (SPPs) at its interfaces. The experimental results were achieved by Mueller matrix spectroscopic ellipsometry. Observed fine tuning of the transverse magneto-optic Kerr opens up new possibilities for the design of compact nonreciprocal devices.

The integration of magneto-optical materials to realize non-reciprocal functions is still a difficult problem, because classical magneto-optical materials require an annealing temperature as high as 700°C. In this framework, this study shows how it is possible to realize efficient magneto-optical mode converter using the association of a magnetic nanoparticles silica/zirconia composite with an ion-exchanged glass waveguide. Using a sol gel process, a silica/zirconia matrix is doped by magnetic nanoparticles (CoFe2O4) and coated on a glass substrate containing straight channel waveguides made by a silver/sodium ion exchange. The extremities of the guides were previously buried using electric field-assisted burial in order to facilitate light injection. Soft annealing (90°C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Depending on the amount of nanoparticles in the composite, on the spatial distribution of the field in the guide and on the modal birefringence of the hybrid structure, the TE-TM conversion varies from several degrees to several tens of degrees.

We describe an immersion grating (IG) with both low polarization-dependent loss (PDL) and high diffraction efficiency. Our immersion grating consists of a silicon (Si) prism and a Si grating coated with dielectric film. We analyze the effect of the refractive index of dielectric film and clarify the refractive index ratio between a Si grating and dielectric film. Selecting an adequate material for the dielectric film, we design the diffraction efficiency of TM polarization without changing that of TE polarization. The simulation results for the optimized IG show a PDL of 0.2 dB and diffraction efficiency of -0.4 dB. A prototype with high dispersion power provides a low PDL of 0.6 dB, while maintaining a high diffraction efficiency of -0.4 dB.

For selected device concepts that are members of an evolving class of photonic devices enabled by guided-mode resonance (GMR) effects, we review physics of operation, design, fabrication, and characterization. We summarize the application potential of this field and provide new and emerging aspects. Our chosen examples include resonance elements with extremely wide reflection bands. Thus, in a multilevel structure with conformal germanium (Ge) films, reflectance exceeds 99% for spectral widths approaching 1100 nm. A simpler design, incorporating a partially etched single Ge layer on a glass substrate, exhibits a high-reflectance bandwidth close to 900 nm. We present a couple of interesting new device concepts enabled by GMRs coexisting with the Rayleigh anomaly. Our example Rayleigh reflector exhibits a wideband high-efficiency flattop spectrum and extremely rapid angular transitions. Moreover, we show that it is possible to fashion transmission filters by excitation of leaky resonant modes at the Rayleigh anomaly in a subwavelength nanograting. A unique transmission spectrum results, which is tightly delimited in angle and wavelength as experimentally demonstrated. We update our application list with new developments including GMR-based coherent perfect absorbers, multiparametric biosensors, and omnidirectional wideband absorbers.

A planar metamaterial Lüneburg lens that enables Fourier optics on-a-chip can be implemented in an SOI slab waveguide structure by patterning the silicon core with variable sized holes. The subwavelength patterning of binary nanocomposite material to form the metamaterial offers the major advantage of fabrication by a single etch step while demanding feature sizes that can be accessed by deep UV lithography in addition to e-beam lithography. A numerical calibration procedure is described that is used to find the relation between fill factor and the local homogenised effective refractive index and which improves upon the predictions of analytic effective media theory used by other researchers. The concept and designs were verified by the 2D FDTD simulation of a two lens telescope system with waveguide feeds implemented in a metamaterial that shows a low insertion loss of -0.45 dB with a reliable field profile at exit. A 3D FDTD simulation of the same two lens telescope system that takes full account of the SOI layers, their finite thickness, and the ridge waveguide feeds also predicts a low loss of -0.83 dB. Less reliance however can be placed on this result due to the coarseness of the computational grid that was necessary. Nevertheless both results are encouraging for planned fabrication trials. This structure can be used in optical transpose interconnection systems in optical switching architectures with the advantage of avoiding large number crossover waveguides in optical communication systems.

A numerical investigation of a two dimensional integrated fiber grating coupler capable of exciting several LP fiber modes in both TE and TM polarization is presented. Simulation results and an assessment of the numerical complexity of the 3D, fully vectorial finite element model of the device are shown.

TeraXion started silicon photonics activities aiming at developing building blocks for new products and customized solutions. Passive and active devices have been developed including MMI couplers, power splitters, Bragg grating filters, high responsivity photodetectors, high speed modulators and variable optical attenuators. Packaging solutions including fiber attachment and hybrid integration using flip-chip were also developed. More specifically, a compact packaged integrated coherent receiver has been realized. Good performances were obtained as demonstrated by our system tests results showing transmission up to 4800 km with BER below hard FEC threshold. The package size is small but still limited by the electrical interface. Migrating to more compact RF interface would allow realizing the full benefit of this technology.

A new photonic integration technique is presented, based on the use of an indium phosphide membrane on top of a silicon chip. This can provide electronic chips (CMOS) with an added optical layer (IMOS) for resolving the communication bottleneck. A major advantage of InP is the possibility to integrate passive and active components (SOAs, lasers) in a single membrane. In this paper we describe progress achieved in both the passive and active components. For the passive part of the circuit we succeeded to bring the propagation loss of our circuits close to the values obtained with silicon; we achieved propagation loss as low as 3.3 dB/cm through optimization of the lithography and the introduction of C₆₀ (fullerene) in an electro resist. Further we report the smallest polarisation converter reported for membrane waveguides ( <10 μm) with low-loss (< 1 dB from 1520- 1550 nm), > 95% polarisation conversion efficiency over the whole C-band and tolerant fabrication. We also demonstrate an InP-membrane wavelength demultiplexer with a loss of 2.8 dB, a crosstalk level of better than 18 dB and a uniformity over the 8 channels of better than 1.2 dB. For the integration of active components we are testing a twin guide integration scheme. We present our design based on optical and electrical simulations and the fabrication techniques.

Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the work piece. Providing closer integration of metrology upon the manufacturing platform can lead to the better control and increased throughput. In this work we present the development of a high precision hybrid optical chip interferometer metrology device. The complete metrology sensor system is structured into two parts; optical chip and optical probe. The hybrid optical chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. The key structure in the device is a tunable laser module based upon an external-cavity diode laser (ECDL). Within the cavity is a multi-layer thin film filter which is rotated to select the longitudinal mode at which the laser operates. An optical probe, which uses a blazed diffracting grating and collimating objective lens, focuses light of different wavelengths laterally over the measurand. Incident laser light is then tuned in wavelength time to effectively sweep an ‘optical stylus’ over the surface. Wavelength scanning and rapid phase shifting can then retrieve the path length change and thus the surface height. We give an overview of the overall design of the final hybrid photonic chip interferometer, constituent components, device integration and packaging as well as experimental test results from the current version now under evaluation.

We demonstrate the feasibility of producing advanced silicon photonic devices for future data communication nodes at 40Gbps using CMOS compatible processes in a 300mm wafer fab. Basic building blocks are shown together with various wavelength division multiplexing solutions. All the devices presented are integrated on 220nm SOI or locally grown epitaxial germanium.

Indium phosphide and associated epitaxially grown alloys is a material system of choice to make photonic integrated circuits for microwave to terahertz signal generation, processing and detection. Fabrication of laser emitters, high speed electro-optical modulators, passive waveguides and couplers, optical filters and high speed photodetectors is well mastered for discrete devices. But monolithic integration of them while maintaining good performances is a big challenge. We have demonstrated a fully integrated tunable heterodyne source designed for the generation and modulation of sub-Terahertz signals. This device is to be used for high data-rate wireless transmissions. DFB lasers, SOA amplifiers, passive waveguides, beam combiners, electro-optic modulators and high speed photodetectors have been integrated on the same InP-based platform. Millimeter wave generation at up to 120 GHz based on heterodyning the optical tones from two integrated lasers in an also integrated high bandwidth photodetector has been obtained.

Mid-infrared (MIR, 2-6 μm wavelength) transparent metal oxides are attractive materials for planar integrated photonic devices for sensing applications. In this study, we present reactive sputtering deposited ZrO₂-TiO₂ (ZTO) thin films as a new material candidate for integrated MIR photonics. We demonstrate that amorphous ZTO thin films can be achieved with Ti concentration of 40 at.%. With increasing Ti concentration, the optical band gap decreases monotonically from 4.34 eV to 4.11 eV, while the index of refraction increases from 2.14 to 2.24 at 1 μm wavelength. MIR micro-disk resonators on MgO substrates are demonstrated using Ge₂₃/Sb₇S₇₀/Zr_0.6Ti_0.4O₂ strip-loaded waveguides with a loaded quality factor of ~11,000 at 5.2 μm wavelength. By comparing with a reference device of Ge₂₃Sb₇S₇₀ resonator on MgO and simulating the optical confinement factors, the ZTO thin film loss is estimated to be below 10 dB/cm. Single mode shallow ridge waveguides with a ridge height of 400 nm and a slab height of 1.7 μm are also demonstrated using ZrO₂ thin films on MgO substrates. The low loss, relatively high index of refraction, superior stability and proven CMOS compatibility of ZTO thin films make them highly attractive for MIR integrated photonics.

We consider a gold nanoparticle chain integrated on a dielectric waveguide. With appropriate geometrical parameters, such a chain behaves as a waveguide. We show that the spatial harmonics generated in the sub-wavelength periodic structure can be locally separated or extracted. This is done by playing with the phase matching condition of the coupling with the dielectric waveguide: only the fundamental component is locally cancelled in the periodic structure, resulting in a non-monotone phase evolution along the structure. Additionnally we show that the analysis of spatial harmonics allows extracting more information on the localized surface plasmon mode generation.

An ultra-compact TE-pass polarizer with an ultra-broad band is proposed theoretically and demonstrated experimentally by utilizing a silicon hybrid plasmonic waveguide. The metal layer of the silicon hybrid plasmonic waveguide is designed to have an F-P cavity as well as a Bragg grating so that the TM-polarized light is reflected efficiently while the TE-polarized light goes through with very low loss. By utilizing the present structure with a metal Bragg grating, the designed TE-pass polarizer is with a size of as small as 0.5 × 3.1 μμm² and the theoretical extinction ratio is as high as 15 dB over a broad band of >200 nm.

In this paper, we introduce slow-light enhanced nanoscale plasmonic waveguide devices for manipulating light at the nanoscale. In particular, we investigate nanoplasmonic metal-dielectric-metal (MDM) waveguide structures for highsensitivity sensors. Such plasmonic waveguide systems can be engineered to support slow-light modes. We find that, as the slowdown factor increases, the sensitivity of the effective index of the mode to variations of the refractive index of the material filling the structures increases. Such slow-light enhancements of the sensitivity to refractive index variations lead to enhanced performance of active plasmonic devices such as sensors. We consider Mach-Zehnder interferometer (MZI) sensors in which the sensing arm consists of a slow-light waveguide based on a plasmonic analogue of electromagnetically induced transparency (EIT). We show that a MZI sensor using such a waveguide leads to approximately an order of magnitude enhancement in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, compared to a MZI sensor using a conventional MDM waveguide.

We propose an integrated power divider/combiner at the interface between silicon nanowire and plasmonic slot waveguide (PSW). The proposed configuration facilitates light access and manipulation in planar nano-plasmonic circuits. The light is incident from a standard silicon nanowire to be accessed by a nano-plasmonic circuit providing subwavelength confinement. The structure overcomes the losses associated with long distance light propagation in nanoplasmonic splitters as coupling and splitting are performed at the same interface with minimal losses. Two PSWs placed orthogonally to the silicon nanowire forming hybrid junctions are exploited for the power dividing/combining functionality. The power splitter has been analyzed using the finite difference time domain (FDTD) numerical method. The ultra-compact proposed device provides wide-band power splitting functionality. A splitting of 34.7%, over most of the wavelength spectrum from 0.8 μm – 2.5 μm, is demonstrated.

Using plasmonic waveguide for interconnects application is very promising direction to achieve high density integration a good size compatibility with electronic devices. Thus, proposing compact and efficient functional plasmonic devices is or prime essential to achieve the required system functionalities. Power splitters are widely used as one of the important component of the optical interconnects and integrated photonic and plasmonics devices. We propose a simple, ultra compact and wideband balanced power divider. The advantage of this device is compactness and ability to split the power over wideband with negligible imbalance. The device is based on plasmonic slot waveguide configuration and has submicron total foot print. To achieve the proposed optimized design, a simple and novel analytical model is utilized for modelling the behavior or any plasmonic structure using circuit model.

We review our recent results on using Atomic Layer Deposition (ALD) in fabrication of nanophotonic waveguide devices. ALD is a unique thin film deposition method providing atomic level control of film composition and thickness, perfect step coverage, and large-area uniformity. We employ the advantages of ALD in connection with Sinanophotonics. We present several new structures based on filling silicon slot waveguides or coating the silicon strip waveguides with ALD-grown materials. Also ALD grown TiO₂ strip waveguides are introduced.

We present easy-to-implement technologies to produce LiNbO3 PhCs in confined optical waveguides. Ti-indiffusion or Annealed Proton Exchange (APE) are combined with optical grade dicing to fabricate ridge waveguides with propagation losses that can be lower than 0.2 dB/cm. Firstly we show how a PhC inscribed in a confined ridge waveguide can be exploited as a temperature sensor with an unexpectedly high 8 nm/°C temperature sensitivity. LiNbO3 PhCs with high aspect ratio are also demonstrated. The performance is achieved by properly tilting the ridge before patterning its walls by Focused Ion Beam (FIB). A eight micrometer long 1D-PhC on a Ti:LiNbO₃ ridge waveguide has been fabricated and its reflectivity has been evaluated using an optical coherence tomography (OCT) system: it is measured to be 53 % for the TM wave and 47 % for the TE wave. The period can be optimized in order to increase the reflection of the 1D-PhC up to 80 %. These developments open the way to the dense integration of compact dynamic devices such as modulators, spectral filters or electric field sensors.

Embedding polymer optical waveguides (WGs) into printed circuit boards (PCBs) for intra-board or board-to-board high speed data communications requires polymer materials that are compatible and inert when exposed to common PCB manufacturing processes. Ensuring both WG functionality after chemical exposure and maintaining PCB manufacturing integrities within the production process is crucial for successful implementation. The PCB manufacturing flow is analyzed to expose major requirements that would be required for the successful implementation of polymer materials for embedded WG development. Chemical testing and analysis were performed on Dow Corning ® OE-4140 UV-Cured Optical Elastomer Core and Dow Corning® OE-4141 UV-Cured Optical Elastomer Cladding which are designed for low loss embedded optical WGs. Contamination testing was conducted to demonstrate polymer compatibility in both cured and uncured form. Various PCB chemicals were treated with uncured polymer material and tested for effective contamination. Fully polymerized multimode WGs were fabricated and exposed to PCB chemicals at temperatures and durations comparable to PCB manufacturing conditions. Chemical analysis shows that the chosen polymer is compatible and inert with most common PCB manufacturing processes.

The development of pulsed lasers allows increasing the power density into integrated waveguides to a level compatible with the generation of nonlinear phenomena, opening the route to the realization of integrated supercontinuum sources. In this paper, we investigate the spectral broadening of a laser pulse through Raman scattering processes in normal dispersion regime with nanosecond pumping. The obtained experimental results are compared to an experimental model based on a single fiber with the same confinement and perspectives in terms of integrated broadband sources are presented.

Ductile regime dicing has been used to machine a variety of optical materials to produce waveguides for lasers, multimode interference devices and non-linear devices. However, few papers discuss the properties of the machining, either qualitatively or quantitatively. In this work ductile regime dicing of germanium, Yttrium Aluminum Garnet (YAG), lithium niobate and silicon for photonic applications are reported. Machining parameters are discussed, surface micrographs shown, and surface roughnesses are calculated for each sidewall machined. The sidewall average surface roughnesses (Sa) were measured to be 2.1 nm for germanium, 3.5 nm for YAG, 7.9 nm for lithium niobate and 8.6 nm for silicon.

Nowadays, in the modern optical communications systems, channel waveguides represent the core of many active and passive integrated devices, such as amplifiers, lasers, couplers and splitters. Different materials and fabrication processes were investigated in order to achieve the aforementioned optoelectronic circuits with low costs and high performance and reproducibility. Nevertheless, the 2D guiding structures fabrication continues to be a challenging task in some of optical materials due to their susceptibility to mechanical and/or chemical damages which can occur during the different steps of the fabrication process. Here we report on channel waveguides demonstration in erbium doped Tungsten – Tellurite (Er³⁺:TeO₂-WO₃) glasses and BGO crystals by means of a masked ion beam and/or direct writing processes performed at different energy MeV and ions species. The evidence of the waveguides formation was investigated by microscopy techniques and micro Raman spectroscopy.

An optofluidic hybrid platform based on hybrid liquid core ARROW waveguides has been fabricated and tested. Solid core hybrid ARROW was integrated in a self-aligned optical configuration with the ARROW optofluidic channel for an improved collection efficiency. The platform was fabricated using a modular approaches. The microfluidic system was completely realized with PDMS using a layered structure while the optical part was realized developing a hybrid silicon/PDMS solution. The performance of the system has been tested by carrying out fluorescence measurements on Cy5 water solutions, obtaining an LOD of 2.5 nM.

An integrated optical sensor is developed for measuring gas concentration for subsea and atmospheric applications. The optical sensor is based on a waveguide Mach-Zehnder interferometer (MZI). In MZI, the light is spilt into a sensing and a reference arm and after a certain distance the branches are recombined. The sensing branch is covered with a sensitive layer that has high affinity towards a specified gas. The presence of the gas gives a change in the refractive index of the sensing arm, which is translated into a change in the output signal. With a prior calibration, the change in the output signal is correlated to the gas concentration. The waveguide should be single-mode and it is desirable to have high intensity in the evanescent field. By using a high refractive index material and a thin waveguide core, the intensity of the evanescent field can be enhanced. Simulations are performed to obtain waveguide parameters with low losses and high sensitivity. The maximum sensitivity at wavelength 785 nm was obtained for a waveguide of core thickness 150 nm, rib height 5 nm and width 1 m for TM polarization. The first measurements of phase sensitivity of 12456π rad/RIU was obtain by the Hydrogen Chlorine (HCl) measurement. This is comparable to the phase sensitivity of 14268π rad/RIU obtained by the simulation.μ

We present the development of a novel semiconductor chip-based spectrometer for calibration of Earth observation instruments. The chip follows the Solo spectroscopy approach utilising an array of microdisk resonators evanescently coupled to a central waveguide. Each resonator is tuned to select out a specific wavelength from the incoming spectrum, and forms a p-i-n junction in which current is generated when light of the correct wavelength is present. In this paper we discuss important design aspects including the choice of semiconductor material, design of semiconductor quantum well structures for optical absorption, and design and optimisation of the waveguide and resonators.

Realization of single-mode waveguides is essential for ultra-sensitive biosensing in the mid-infrared molecular “fingerprint” region for biomedical lab-on-chip applications. High contrast (Δn ≈ 1) germanium telluride (GeTe₄) single mode rib waveguides were fabricated on zinc selenide (ZnSe) substrates for evanescent field based sensing to detect analytes at low concentration. Amorphous GeTe4 thin films were deposited by RF-sputtering and were found to transmit over the spectral range from 2μm - 20μm. Photolithography followed by reactive ion etching was carried out to etch the film, forming rib waveguide structures with minimum surface roughness and vertical sidewalls. It was found that films deposited at room temperature have average roughness of about 5nm. Optical constants were determined by IR-VASE ellipsometry.

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, EMI immunity, high sensitivity, and multiple multiplexing schemes, as compared to conventional electricity based strain sensors. FBG sensors written in Polarization Maintaining (PM) optical fiber offer an additional dimension of strain measurement simplifying sensor implementation within a structure. This simplification however, adds complexity to the detection of the sensor’s optical response to its corresponding applied strain. We propose a modified Transfer Matrix Method model to simulate a fiber Bragg grating (FBG) in a polarization maintaining optical fiber. We study the effects of the reflected Bragg wavelength to the changes in shape of the optical fiber core waveguide and compare the results to the existing literature.

Two types of optical sensor based on one-dimensional Photonic Crystal (PhC) stack nanobeam cavity has been designed, fabricated and characterized. One-dimensional PhC stack nanobeam cavity with measured Q-factors up to 27000 and a sensitivity of 270nm/RIU has been demonstrated. Then, we introduce a finite width slot between two periodic arrays of the dielectric stacks. Thus, the majority of optical field distributes in the slotted low-index area and the light matter interaction with the analytes has been enhanced. A sensitivity of 410nm/RIU has been achieved while maintaining the Q-factors near 10⁴.

We discuss heterogeneous integrations and their impacts on computing, networking, and imaging applications. We will review photonic integration technologies including silicon, InP, GaAs, SiO₂, Si₃N₄, and magneto-optical materials such as YIG and BIG. We will address new architectures, new capabilities, and performance enhancement brought into computing, networking, and imaging architectures through heterogeneous photonic integration.

Mesoscopic photonic crystal based mirrors are exploited to theoretically conceive and analyse a novel high-Q factor Fabry-Perot-like cavity. Thanks to a beam focussing effect in reflection these mirrors efficiently confine and stabilise a mode inside a planar cavity, even for non-paraxial small beam sizes, mimicking the behaviour of curved mirrors. Furthermore, these mirrors show a higher reflectivity with respect to their standard distributed Bragg reflector counterparts, which allow these cavities to reach a maximum Q factor higher than 10⁴ when 5-period-long mirrors are considered. Moreover, these cavities show other intriguing features as a beamforming behaviour and transverse translational invariance offered by the planar geometry. The latter opens interesting possibilities for lasing and biodetection. The optimization of the cavity size and the performances in terms of Q factor, energy storage and confinement are detailed.

A modified SAG technique is reported for the fabrication of DWDM MWLAs. The 20-channel DFB laser arrays with 0.22nm and 0.44nm channel spacings are respectively obtained, which is promising for fabrication of low cost MWLAs.

A waveguide sensor using a gapped optical fiber for measurements of refractive index and absorptance of liquid has been theoretically investigated. The gap formed in the single mode optical fiber is filled with the liquid whose optical characteristics are to be measured. An optical loss of the gapped optical fiber depends on the refractive index and absorptance of the liquid in the gap. The optical loss becomes smaller with the refractive index of the liquid as the light beam greatly expands in the media with smaller refractive index because of diffraction. On the other hand, the optical loss becomes larger with the absorptance of the liquid. Therefore, the refractive index and absorptance can be measured by using two waveguide sensors with different gap width. In the previous work, we investigated the theoretical characteristics of the sensors by using the two-dimensional slab waveguide for simplification. In this work, we have derived an equation for evaluation of the optical losses by approximating the fundamental mode in the optical fiber by a Gaussian function for practical use. And we clearly show the relationship between the optical loss and the refractive index of liquid filled into the gap for various gapped optical waveguides. The optical loss more greatly changes in the gaped optical fiber in comparison with the gaped slab waveguide. We have designed a saccharimeter for the liquid with Brix scale 0–20% by using the gapped waveguide. For example, the optimum gap widths are evaluated as 1.8 mm for the spot sizes of 0.01 mm. We have also designed waveguide sensor for measurements of not only refractive index but also absorptance of liquid.

Gradient index (GRIN) structures have attracted great interests since their invention. Especially, the recent advance in the fields of transformation optics, plasmonics, and nanofabrication techniques has opened new directions for the applications of GRIN structures in nano-photonic devices. In this paper, we apply Luneburg lens and its transformed counterpart to realize efficient coupling to plasmonic nano-waveguides. We first briefly present the general structures of Luneburg lens and generalized Luneburg lens, as well as the design process of flattened Luneburg lens applying quasiconformal mapping techniques. After that, we study the performance of these lenses for coupling electromagnetic signals to nano-waveguides (the metal-insulator-metal (MIM) nano-waveguide), and different schemes are investigated.

A silicon optical modulator operating at high speed and low voltage is proposed by using a Schottky diode. The optical modulation is achieved by the intensity change of guiding light due to free-carrier absorption, not conventional interference effects. The rib waveguide structure of the modulator has a height of 340 nm, a etch depth of 150 nm, a width of 4.8 μm, and a modulation length of 500 μm. It was designed to maximize the free carrier injection by a Schottky contact on the rib waveguide center. The center of the rib waveguide is lightly doped with phosphorus of 10¹⁶ cm⁻³, and the sides are heavily doped with phosphorus of 10²⁰ cm⁻³ to improve modulation depth by injecting free carriers into the center of the rib waveguide. This design allowed a high overlap between the optical mode and carrier density variations in the center of the waveguide. To achieve high speed operation, travelling-wave type electrodes were designed to allow co-propagation of electrical and optical signals along the waveguide. The device simulated results demonstrate a 3.3 dB modulation depth for a 500 μm modulation length with 3 V_pp driving voltages. We demonstrated a Schottky modulator operating Si EAM at 3 V_pp with a 3 dB bandwidth of 7 GHz.

For small radius ring resonators, the estimation of the resonance wavelength and Free Spectral Range FSR using the group index fails to give accurate results consistent with the FDTD calculation. In this work we present a new formula for the calculation of these parameters. The formula is based on the expansion of the ring effective index as a function of the wavelength and then solving the resonance equation to get the resonant wavelength and the FSR. Using this form, the error in estimating the resonance wavelength is reduced from 5.7% to less than 0.3% when compared with the FDTD calculation.

We use an inverse-scattering (IS) approach to design single-mode waveguides with controlled linear and higher-order dispersion. The technique is based on a numerical solution to the Gelfand-Levitan-Marchenko integral equation, for the inversion of rational reflection coefficients with arbitrarily large number of leaky poles. We show that common features of dispersion-engineered waveguides such as trenches, rings and oscillations in the refractive index profile come naturally from the IS algorithm without any a priori assumptions. Increasing the leaky-pole number increases the dispersion map granularity and allows design of waveguides with identical low order and differing higher order dispersion coefficients.

Waveguide Mach-Zehnder interferometers (MZI) have been successfully used for a number of sensing applications due to their high sensitivity. As the MZI-sensors have a built-in reference, they are ideally not dependent on temperature variations. However, due to their high sensitivity, a temperature difference or an imbalance between the two arms, can give an unwanted temperature dependence of the output signal. Here, we present an experimental study of the temperature sensitivity of waveguide MZI. Three designs, balanced MZI, unbalanced MZI and tapered MZI are studied. In order to investigate the temperature sensitivity of the interferometer, we measure the phase shift at the output of the interferometer as function of temperature. It is found that the balanced MZI is very stable with temperature. For an unbalanced MZI having a 1 mm length difference between the two arms, a small phase shift is observed. The phase shift was less than one period for a 10°C change. The phase shift can be precisely determined for the tapered MZI. Initial measurements of the temperature sensitivity for a balanced, tapered MZI, gave output variations of some 150° for the phase, for a temperature change of 10°C. This corresponds to a temperature difference of 2.6 mK within the oil covering the two arms and demonstrates how sensitive the device is to temperature differences between the sensing and the reference arms.

Broadband nanostructured metallic-dielectric absorbers and reflectors are of great interest in integrated optics and they have a great potential for applications like polarizers or reflectors for nanoantennas applications operating in optical frequencies, covering the interval of the O-E-S-C-L-U bands. In this work, novel geometric and optical configurations are numerically analyzed. The absorber or reflected central frequencies of the analyzed devices can be easily tuned over the entire communications wavelength band by varying their geometrics and optical parameters Peaks of absorption larger than 80% were obtained in optical wavelengths by using metals like silver and gold in combination with silica substrates.

In this paper, we present a detailed analysis about the electro-optic (EO) polymer modulators using a full vectorial finite difference (FVFD) mode solver for an optical waveguide and a finite-element method (FEM) for a microwave electrode. A detailed discussion has been presented to describe a modulator about performance parameters: V_πL, ΔfL with the design parameters, where V_πL is the product of the half-wave voltage V_π and the electrode interaction length L, the parameter ΔfL is the product of the 3 dB optical bandwidth Δf and the electrode interaction length L.