This PDF file contains the front matter associated with SPIE Proceedings Volume 10814, including the Title Page, Copyright information, Table of Contents, Introduction, Author and Committee lists

Semiconductor laser diodes have been widely used for digital optical signal processing and microwave photonics. Most of the applications using semiconductor laser diodes use optical injection locking techniques with positive wavelength detuning. Recently, injection locking with negative wavelength detuning is getting attention for various applications. In this paper, we analyzed injection locking in single mode Fabry-Pérot laser diode with both positive and negative wavelength detuning. Based on the analysis, applications of both injection-locking techniques are identified in the field of digital photonics and microwave photonics. As an application of injection locking with positive wavelength detuning, we propose a memory accessing technique, which includes digital blocks such as decoder, switch and a SR latch using positive injection locking whereas microwave generation technique is proposed using negative injection locking.

Quantum dot (QD) solids are promising materials for the development of optoelectronic devices, in particular solar cells. The efficiency of such devices depends strongly on the energetic disorder within QD solid due to QD size variance and matching the energy of the components. Here, we studied optical properties, such as absorption, luminescence, timeresolved luminescence spectra, and electrical conductivity of QD solid layers made of PbS QDs of different sizes (2.9 nm, 4.1 nm and 5.1 nm) as well as QD solid layers with QD size gradient. We discussed the efficiency of energy and charge transfer in layers with QD size gradient by performing theoretical estimates of the appropriate parameters. Additionally, we fabricated photovoltaic solar cells based on the QD solids and investigated an influence the energy disorder on the conductivity and the efficiency of solar cells.

We present a silicon-on-insulator (SOI) based device that exhibits Fano resonance with high extinction slope rate (SR) and extinction ratio (ER). It is constructed by using two cascaded tunable Mach–Zehnder interferometers (MZIs). The first MZI is used to adjust the power splitting ratio of the second MZI. In the second MZI, two add-drop microring resonators (MRRs) are located in each arm of the second MZI, respectively. The MRRs are used to generate a high-Q and low-Q resonance respectively. Due to the interference between these two resonances, a Fano resonance could be implemented. Considering that the optical power splitting ratio and phase difference between the two resonances can be finely adjusted, the ER can be greatly increased. In the experiment, the measured Fano resonance of the fabricated device exhibits simultaneous ER of 41.5 dB and SR of 3388.1 dB/nm. To the best of our knowledge, this is the first time to achieve a Fano resonance with such high ER and SR simultaneously. By adjusting the bias voltage in the fabricated device, a pair of complementary Fano resonance line shapes can be achieved.

We developed a novel lab-on-a-chip device with the capability of rapidly antibody determination that use nano-beads as the solid carriers. The device combines a plasmon-assisted optical conveyor belt in the main microfluidic channel, which is made of gold nano-ellipses perpendicular to each other. In the presence of an external uniform electric field, the hot spots in the belt function as optical tweezers can trap and transport properly sized nano-beads with target antibody combined along a fix direction through rotating the polarization. Several branch channels intersecting the main microfluidic channel at right angles are used to transport smaller antigen modified nano-beads, which can be labeled with fluorescent dyes. When arriving at the crossings, the smaller nano-beads would be trapped by hotspots on the surface of two-dimensional ellipses arrays around the conveyor belt and can’t be transported between two ellipses due to their smaller size. So, the antibody modified nano-beads would be transported along the optical conveyor belt and encounter the trapped antigen modified ones in the ellipses arrays successively. Only those ones with specific antigen combined that stick to the antibody to be measured can be dragged by bigger nano-beads and transport with it. In light of that, we can determinate the antibody by identifying the fluorescence-labelled nano-beads at the exit of the main channel. With the capacity for parallel detection, our design offers an attractive scheme for rapid, high throughput determination of antibody in microfluidic channels, which are also ease to operate.

Publisher's Note: This paper, originally published on 11/5/2018, was replaced with a corrected/revised version 11/15/2018. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.

We present some recent developments using smart optical tools, such as optical fiber tweezers (OFTs) and plasmonic optical antennas, to explore the biological world. Using OFTs, which act as a smart light touch, we realized the stable trapping and flexible manipulation of single particles, bacteria, and cells. The trapping and multifunctional manipulation is demonstrated using different samples varying from mammalian cells to bacteria, nanotubes and to biomolecules, with sizes changing from several tens of micrometer to a few nanometer. The OFTs is also used for the stable trapping and patterning of multiple particles and cells, with the ability of biophotonic waveguides formation based on bacteria. In addition to the trapping and manipulation of cell individuals, we also demonstrated that smart optical tools, such as plasmonic optical antennas, are capable of cellular exploration.

A cantilever-based microring laser structure was proposed for easily integrating III-V active layer into mechanically stretchable substrates. Local strain gauges were demonstrated by embedding cantilever-based microring lasers in a deformable polymer substrate. The characterizations of microscale local strain gauges had been studied from both simulated and experimental results. The lasing wavelength of strain gauges was blue-shift and linear tuned by stretching the flexible substrate. Gauge factor being ~11.5 nm per stretching unit was obtained for a cantilever-based microring laser with structural parameters R=1.25 μm, W₁=450 nm and W₂=240 nm. Such microring lasers embedded in a flexible substrate are supposed to function not only as strain gauges for monitoring the micro- or nano-structured deformation, but also tunable light sources for photonic integrated circuits

Hybrid plasmonic waveguide (HPW) has received extensive attention recently due to its excellent performance of tight field confinement and low propagation loss. In this work, the transmission spectra of hybrid plasmonic waveguide Bragg gratings (HPWBGs) composed of two alternately arranged low refractive index dielectric materials are studied, combining the finite element method (FEM) and transfer matrix method (TMM). Meanwhile, by changing the width of the outermost layer of the waveguide, the influence on transmission spectra under different optical admittance matching conditions are discussed through admittance matching theory. Theoretical calculations and simulation results show that a specific thickness of the matching layer has a specific influence on the pass band or the forbidden band of a specific frequency range on the transmission spectrum. The transmission characteristics of the low-frequency or high-frequency pass band and the band gap can be optimized by adjusting the thickness of matching layer to obtain the admittance match or mismatch conditions. This result provides a good theoretical basis and design method for preparing photonic devices for requirements in different wavebands.

Photonic integrated circuits suffer from a thermal drift of device performance, which is a key obstacle to the development of commercial optoelectronic products. Temperature-insensitive integrated waveguides and resonators have been demonstrated at a single wavelength, using materials with a negative TOC, which are not suitable for WDM devices and wideband nonlinear devices. Here, we propose two waveguides to realize the generation of broadband athermal features. For one of them, the temperature-insensitivity over a bandwidth of 780 nm (1280 to 2060 nm) with an ultra-small effective-TOC within is ±1×10^-6/K. Uniquely, the waveguide has small anomalous dispersion (from 66 to 329 ps/nm/km) over the same band and is suitable for frequency comb generation without being affected by intra-cavity thermal dynamics. We also show another waveguide design with an effective-TOC variation of ±1×10^-6/K over a bandwidth of 1060 nm, from 1220 to 2280 nm. The obtained dispersion varies from -232 to -502 ps/nm/km over the same band, which can be used in nonlinear devices.

We present an analysis of the effects of lateral misalignment on the performance of butt-coupling between a 6-mode step-index circular-core fiber and a matched 6-mode square-core waveguide. For a typical 6-mode fiber with a core index of 1.4540, a cladding index of 1.4440, and a core diameter of 13.1 μm, low modal crosstalk (–20 dB) butt-coupling can be achieved with a lateral misalignment smaller than about 0.4 μm.

A three-dimensional tapered silicon-based spot-size converter is studied to improve the butt-jointed efficiency between the laser diode and the single-mode silicon waveguide. This kind of the spot-size converter can be fabricated while the ridge waveguide is etched. There is no need to regrow SiN or SiON on silicon. The optimized coupling efficiency between the spot-size converter and laser diode is over 0.8 at the wavelength of 1550 nm. This spot-size converter is useful for silicon photonics.

Q-factor in optical resonators is important issue that quality the device and the type of applications. Due to the advantages of optical resonators in terms of reproducibility on chip (that are designed of various topologies and integration with optical devices), it is very important to get a highest Qfactor. To increase this factor from the lower rang [10⁴ - 10⁶] to higher one [10⁸ -10¹⁰] we use crystalline resonators. In practice, it is more complicated to couple an optical signal from a tapered fiber to crystalline resonator than from a defined ridge to a resonator designed on a chip. In this work, we will focus on the simulation and optimization of the crystalline resonators under straight wave guide and subject also to technological constraints of manufacturing. The coupling problem at the Nano scale makes our optimizations problem more dynamics in term of design space.

Modeling of waveguide AlInAs avalanche photodiodes is reported in this work. Based on beam propagation method analyses, the waveguide design and evanescent coupling are investigated at first. The APD dark- and photo-response and multiplication gain are further simulated based on a drift-diffusion method. The frequency response and bandwidth are also evaluated based on carrier transit analysis formalism. Modeling results of I-V curves, multiplication gain, breakdown voltage, excess noise factor, -3dB bandwidth and gain-bandwidth product are presented with some consistently compared with reported experimental demonstration.

We propose a freestanding GaN-based integrated photonics chip with ultra-micro LED and straight waveguide for visible light communication on GaN-on-silicon platform realized by double-side process. The ultra-micro LED and waveguide is prepared by dry etching for GaN, electron beam evaporation for metal electrode, plasma enhanced chemical vapor deposition (PECVD) and wet etching for SiO2. The silicon substrate under chip is totally removed by deep inductive coupled plasma (ICP) etching to realize the freestanding membrane. The ultra-micro LED emits visible light signal in blue range. The visible light signal is coupled into straight waveguide connected to ultra-micro LED, and transmitted to tip of waveguide end. The communication performance of chip is significantly influenced by the active area of LED. Ultra-micro LED could well confine the visible light signal in waveguide, and achieve greater modulation bandwidth. The technical difficulty of chip with ultra-micro LED is to make p-electrode pad on active area with ultramicro size. We realize p-electrode pad with relatively large size on ultra-micro LED with SiO2 isolation layer. Light transmission performance of chip verse current is quantitatively analyzed by measuring intensity of visible light transmitted to waveguide tip. Most of the light emitted from ultra-micro LED is well confined in straight waveguide. The light intensity of waveguide tip is strongly modulated by the geometric parameters of straight waveguide. Freespace visible light communication (VLC) test with 120Mbps random binary sequence is carried out to achieve high speed data transmission. This study provides a potential approach for GaN-based integrated photonics chip as ultramicro light source and passive optical device in visible range.

A vital signs monitor based on few-mode fiber (FMF) is presented in this paper. Two types of FMF, dual-mode fiber (DMF) and four-mode fiber are respectively utilized for vital signs monitoring. For DMF, core-offset distance between lead-in single mode fiber (SMF) and DMF was optimized numerically, the results of which agree very well with experiments and respiration ratio can be measured successfully with acceptable extinction ratio. For four-mode fiber, core-offset mode excitation method with optimized parameters is also utilized to excite four types of modes, LP01, LP11, LP21 and LP02, which realizes the modal interference enhancement and the extinction ratio can reach 10 dB. Breath signals can be also detected using this structure. As demonstrated in this paper, FMF-based sensor could provide a promising candidate for fiber-optic biomedical application.

A new type of fiber acoustic sensor (hydrophone) is exhibited here with two fiber Bragg gratings (FBG) and a unique demodulation method. Almost all former FBG sensors had separated detecting and demodulating components while this FBG hydrophone has an idiomatic structure for both detecting and demodulating method, it utilizes a couple of same cascaded FBGs, as well as a barrel shaped structure. The physical form of the hydrophone helps us to overcome the effects of temperature noises and it will even help us for localization purposes in future works. We successfully reached more than 0.5nm/MPa sensitivity which is appropriate for environments with less than 200dB pressure.

The self-sweeping laser is the simplest sort of tunable laser without use of optical elements and electrical drivers for frequency tuning. Owing to broad sweeping range (more than 10 nm) and simplicity, self-sweeping fiber lasers are attractive sources for applications demanding tunable radiation such as sensors interrogation, spectral analysis, optical frequency domain reflectometry and so on. Currently the self-sweeping effect in fiber lasers was observed in different spectral regions covering range from 1 to 2.1 μm. In the paper, linearly-polarized Tm-doped fiber laser with sweeping range of more than 20 nm in the region of 1.92 μm has been experimentally demonstrated. The laser is based on singlemode polarization-maintaining Tm-doped fiber and pumped by home-made Er-doped fiber laser with wavelength of 1540 nm. The cavity is formed by highly-reflective fiber loop mirror and right-angle cleaved fiber end. The main feature of the laser is generation of periodic μs-scale pulses where each of them contains practically only single longitudinal mode radiation with linewidth of ~1 MHz. The laser frequency is changed from pulse to pulse by one intermode beating frequency of the laser ~8 MHz. The sweeping rate is increased with pump power up to 10 nm/sec. The average output power exceeds 400 mW. The developed laser source can be used for atmospheric remote sensing as well as for interrogation of the sensors based on fiber Bragg gratings and is applied to measure spectrum of water absorption lines in air.

In this paper, the forward Brillouin scattering frequency shifts of step-index fibers and photonic crystal fibers (PCFs) with different core diameters is investigated by numerical simulation. The multiple Brillouin scattering peaks with the range from 20 to 800 MHz are generated in the step-index fibers. We find that there are no changes in Brillouin scattering frequency shifts when the core diameter is changed, but the scattering efficiency is different. In the PCFs with periodic air holes, there are a few dominant peaks and the frequency shifts vary with the core diameter changing. For the core diameter of 11.6 μm, there are three peaks at 327.39, 556.48 and 824.14 MHz, respectively. When the core diameter decreases to 2.32 μm, the frequency shifts of the forward Brilloun scattering are 1.619, 2.779 and 4.123 GHz, respectively. The core diameter of the PCFs can affect the frequency shifts of the forward Brilloun scattering and the frequency shifts increase with the core diameter decreasing. The difference between the step-index fibers and PCFs results from the influence of the fiber microstructure on the guided acoustic wave. Our simulated results will be instructive for the design of fiber microstructure.

The evolution of the degenerate four-wave mixing (DFWM) effect in tellurite photonic crystal fiber (PCF) is investigated systematically. The influence of the pitch distance Λ 1 to 10μ) and the diameter-to-pitch ratio p (from 0.2 to 0.99) on the phase matching condition is analyzed numerically. The evolution of DFWM parameters including the output signal power, signal gain, output idler power and idler conversion efficiency is investigated by changing the fiber length Z (from 2 to 10 m), signal wavelength (from 1.26951 to 1.27012μm idler wavelength (from 1.9980 to 1.9995 μm), initial pump power (from 5 to 15 W) and initial signal power (from -10 to 30 dBm). The pump, signal and idler waves propagate in the fiber with a gradually decreasing period. Based on DFWM occurring in the proposed tellurite PCF (=3.3 μm p =0.75), the signal (anti-Stokes wave) is efficiently amplified and the idler (Stokes wave) is efficiently generated at the mid-infrared (mid-IR) wavelength with the pump wavelength of 1.553 μm. The signal gain can be increased by increasing the initial pump power. The idler conversion efficiency has an upper limit of 25.95%. The simulated results will be instructive for the experimental FWM process to generate mid- infrared lasing.

Femtosecond control of electron spin not only promises the capability of satisfying the ever-increasing demand of storage information and ultrafast manipulation of magnetization in mediums, but also delivering controllable, highlyefficient, cost-effective and compact terahertz sources. Femtosecond spin dynamics have been extensively investigated these years with the methods of ultrafast magnetic-optical Kerr effect, inverse Faraday effect, inverse spin Hall effect and so on. Recently emerged coherent terahertz emission spectroscopy can also be employed to study this ultrafast spin dynamics with its unique advantages. For example, terahertz emission spectroscopy is a coherent, time-resolved, contactless Ampere-meter, which can be used to deduce the spin-charge conversion. However, femtosecond laser interaction with magnetic mediums is a rather complex process, there are still lots of physical mechanisms waiting to be unveiled. Here, we systematically investigate the femtosecond spin dynamics in ferromagnetic materials via polarization-resolved terahertz emission spectroscopy. We obtain detectable electromagnetic field radiation with its polarization parallel to the external magnetic field direction, which was not observed in the same materials in previous work. Inverse spin-orbit torque tilting is responsible for the observed phenomenon. Based on this mechanism, the efficiency and polarization of the generated terahertz waves can be coherently controlled and manipulated not only by the external magnetic fields, but also by the sample structures and the pumping femtosecond laser pulses. Our work not only helps further deepen understanding of the physical mechanism of all-optical magnetization reversal, boosting future spin recording technology, but also offers a very promising way for developing novel and efficient terahertz functional sources and devices.

The break-down voltage is critical for the reliability and the impact ionization of the 4H-SiC avalanche photodiodes (APDs). In this paper, we report a simulation for 4H-SiC p⁺-n APDs, study the effect of the doping concentration and thickness of the absorption and multiplication region on break-down voltage and gain. We find that with the doping concentration increasing, the break-down voltage decreases, the gain firstly increases and then decreases. When the thickness increases, the break-down voltage firstly increases and then keeps constant due to the width of the depletion region. By adjusting the break-down voltage, the performance of the 4H-SiC APDs can be optimized.

A wavelength-tunable small form-factor pluggable (SFP) optical module is proposed and implemented, which is based on a self-designed 4-channel DFB laser array. The module adopts the widely used SFP packaging standard so that it is convenient to connect with other devices. It has an I2C interface for receiving wavelength tuning commands and downloading digital diagnostics monitoring information to the host processor. Three parts are included: the receiver, the transmitter and the microcontroller unit, to complete the conversion of optical-electro, electro-optical. A large range and high precision wavelength tuning is realized through innovative tuning methods. Two wavelength tuning methods are utilized: channel switching of 4-channel for coarse tuning and temperature tuning combined with current tuning for fine tuning to actualize the tunable output of the DFB laser array. This wavelength-tunable SFP optical module can replace several fixed wavelength optical modules in a traditional WDM system, thus greatly reducing costs and improving the utilization ratio of resources. Experimental results show the SFP optical module can achieve the continuity of wavelength tuning covering 1539.0 nm to 1551.0 nm. It can switch over 16 channels in a 100G-DWDM system or 31 channels in a 50G-DWDM system. The side mode suppression ratios (SMSRs) of most channels are above 40dB over the wavelength tuning range of 12 nm. The optical signal transmission rate is up to 1.25Gbps.

To overcome existing limitations in sensitivity and cost of state-of-the-art systems, new-style device structures and composite material systems are needed with low-cost fabrication and high performance. Vertical field effect photodetectors are fabricated with Au/Ag nanowires as the transparent source electrode and with vertically stacked layers of CsPbBr₃ and lead sulfide quantum dots, which formed heterojunctions. The built-in electric field in the layered heterojunction aids the separation of photoinduced excitons, while the short channel enables efficient carrier transport across the active region. Both of these benefits enable a high photo performance and fast photoresponse. This vertical phototransistors exhibit a wide response spectrum from 400 to 2100 nm, a high photoresponsivity of more than 9 × 10⁸ AW⁻¹, and a high detectivity of up to 2 × 10¹⁷ Jones (cm Hz^1/2 W⁻¹) under infrared illumination. Additionally, this vertical phototransistor had a response time of 3 μs. The solution –based fabrication process and excellent device performances strongly underscore vertical architecture combined with the layered heterojunction as a promising approach for future photodetection field.

Silicon photonics is poised to revolutionize many application areas, such as telecommunication, date centers, biosensing, high performance computing, etc. A whole silicon photonics process flow based on 200mm CMOS platform and the performance of photonics devices were described in this paper. A series of optimized process, including photolithography, etching, hydrogen annealing, ion implantation, epitaxial growth, etc., are implemented to fabricate low-loss passive devices and high-speed active devices. The propagation loss is sensitive to sidewall roughness originated from the waveguide-patterning process. Hydrogen annealing is an effective method to reduce the propagation loss of waveguides. Every level of implantation in top silicon layer is performed respectively, including the p++, p+, p, n++, n+ and n doping for the modulators, p++, p+, n++ and n+ implants for Ge photodetector. Epitaxial Ge is considered to be an excellent material for photodetectors. High-quality Ge on silicon is grown via selective epitaxy using SiO2 as growth mask, followed by a CMP process to planarize the top of the selectively grown Ge. In our platform, the propagation loss of waveguide is measured to be 2.5dB/cm, the insertion loss of grating coupler at 1550nm is 4.5dB/facet, the crosstalk of cross waveguide is lower than -30dB, the insertion loss of 8 channels 200GHz AWG is approximately 3.3dB, the 3dB bandwidth of MZ modulator achieves higher than 20GHz, and the Ge photodetector operates at high data rate exceeding 40Gbps.

Publisher’s Note: This manuscript, originally published on 5 November 2018, has been withdrawn by the publisher for editorial reasons.

Reported for the first time is study of a femtosecond Er:fibre laser with recently proposed drop-shaped cavity allowing spectral tuning of output across 78 nm. The developed configuration ensures reliable (without mode locking collapse or output power glitches) and high-quality (signal-to-noise ratio of intermode beats >58 dB) mode locking over the entire tuning range with low variation of output pulse duration (535–770 fs), making this laser a promising tool in applications that require broad-range continuous spectral tuning of femtosecond pulses. An additional feature is the possibility of continuous adjustment of the output pulse repetition rate, important in metrological applications.

The results of optical designs of objectives for budget light microscopes are presented, including for providing special methods of contrasting. For the design, original optical constructions are applied.

We report three kinds of surface passivation for AlxInyAsSb APD, which are SiO₂, SiO₂ after sulfuration and SU8 2005 treatments. A good sidewall profile of mesas were etch by Inductively Coupled Plasma (ICP) to 2.6μm depth. The order of dark current for device with SU8 passivation is less than -12 under the temperature of 100K. Dark current and photocurrent increase linearly with diameter of mesa. Also, the devices with different passivation methods produce photocurrent excited by incident power. The measurements are consistent with CV modeling and electric field simulations.

To improve the quality of optical resonator's fabrication, an important step consists in performing an annealing process up to 600°C. It improves the roughness of resonator's surface down to the nanometer scale. Concretely it helps in reducing stresses at the periphery of their surface thus allowing higher Q-factors. Mechanical treatments enable state-of-the art characteristics for the surface roughness. The design of an oven strongly depends on its ability to reach the desired annealing process. It is significantly improved thanks to nichrome resistant alloy wires and special chopped basalt fibers for thermal isolation. In addition to the experimental tests, and in order to get better understanding of the residual stresses inside the resonator, we have simulated the heating process in the oven using the finite element code ANSYS© and CFD fluid module. Thermal distribution at different times of the heating and for three different temperatures with the range of 600°C are described.

To obtain high quality factor optical resonator, we must reduces stresses at the periphery of their surface as mechanical treatments enable state-of-the art characteristics for the surface roughness. This process is driven by electronics significantly improved thanks to electronic boards based on the use of intensity pulses, coupled with feedback on several parameters for fitting the specific profile of the heating cycle. Sensor is based on K-type technology to reach specification up to 1000°C. Technology is based on the use of microcontroller, low noise operational amplifiers, field effect transistors and diode bridges and driven by a intensity signal.

This paper discusses the DITMS and the relationship of ion trap volume and its capacitance, it is portable in practical application. The DITMS can be realized at ±2,000V, its volume is smaller than 30cm*30cm*30cm, there is no need to decrease temperature with helium, the measurement range is large, the instrument saves the cost of investment by a large margin. As a scientific instrument, the accuracy of measurement is very important, and this instrument has very exact accuracy and very small volume and very low cost. We only discuss the electronic circuits in the paper, the theory of chemistry please refer to the reference. The photodetectors are used in the DITMS.

With the maturity of germanium (Ge) growth on Si, Ge photodetectors have drawn great interests worldwide, which are potentially used in NIR/MIR light detecting, optical telecommunications, single photon detecting, biosensor applications. Lateral and vertical structured Ge-on-Si PIN photodetectors were fabricated and investigated. A dark current density of 20.4 mA/cm² was obtained, and small size devices resulted in low dark current values. The responsivity as a function of the wavelength was tested, and the highest responsivity of 0.8 A/W at the wavelength of 1310nm was obtained in vertical structured photodetectors, while the lateral structured photodetectors had the best 3dB bandwidth of 0.5 GHz, which was evaluated from the response time of 0.7 ns. The quantum efficiency was ~76%, and the reason of low 3dB bandwidth was discussed.

A compact all-dielectric metasurface lens based on a conventional multimode fiber is proposed and demonstrated. Here, an aperiodic array of rectangular dielectric nanoresonators deposited on the end face of a multimode fiber was used to construct an all-dielectric metasurface lens. By varying the widths of rectangular resonators full 2π phase control was realized. The dielectric resonators were used as phase shift elements to achieve the required phase accumulation through propagation over a subwavelength distance and modulate the phase distribution of the emitted light from the multimode fiber in near-infrared communication band. The proposed all-dielectric metasurface lens exhibits miniaturization and excellent performance, which is key to realize optical trapping, holographic display, and beam shaping. The presented design of all-dielectric metasurface lens can be widely applicable to any high-index semiconductor or insulator and can be applied at any desired wavelength.

This work reports the integration and experimental performance analysis of wavelength division multiplexing passive optical network (WDM-PON), compatible with radio over fiber (RoF) technology. Fixed mobile convergence has been discussed, focusing on how to use available fixed and mobile access infrastructures to meet the requirements of future broadband networks. The proposed architecture enables to simultaneously transport RF and baseband signals through a single-mode fiber (SMF). Optical carrier suppression (OCS) modulation scheme has been proposed to improve the spectral efficiency. Bit error ratio (BER) of 10^-4 has been obtained at 1 Gb/s date rate under the transmission of 25km.

We investigate numerically supercontinuum generation (SCG) pumped by different optical modes in AsSe₂-As₂S₅ chalcogenide microstructured optical fibers (MOFs). The influence on SCG is analyzed numerically by different optical modes including the fundamental and high-order modes. We simulate and analyze the evolution of the supercontinuum (SC) at different pump wavelengths (2120 nm, 2580 nm and 3280 nm) and different optical modes (LP₀₁, LP₁₁, LP₃₁). The pump peak power is from 200 to 1000 W in the MOFs with different core diameters. We also simulate the evolution of SCG with the fiber length. The different optical modes cause the variation of the chromatic dispersion profile and the effective nonlinearity, which induces different mechanisms of the SCG and changes the spectral range. For the LP₀₁ mode, the simulated maximum SC spectral range covers 10.375 μm from 1.875 to 12.250 μm when pumped at 3280 nm with the peak power of 1000 W. For the LP₁₁ mode, the maximum SC spectral range is obtained when pumped at 3280 nm with the peak power of 1000 W, which covers 12.931 μm from 1.389 to 14.320 μm. For the LP₃₁ mode, the maximum SC spectral range is from 1.267 to 3.980 μm when pumped at 2120 nm with the peak power of 1000 W. The widest SC spectral range is obtained when pumped by the LP₁₁ mode. The simulated results will be instructive for the experimental SCG up to the mid-infrared waveband longer than 10 μm.

The wideband design of the anisotropic acousto-optic deflectors in different frequency bands is studied. By solving the Dixon equation of the geometric relationships of Tellurium dioxide crystal, the wideband design parameters of the anisotropic acousto-optic deflector at low frequency band and high frequency band are obtained systematically. The research results show that different linear properties of the bandwidth and central frequency can be observed under different frequency band, this research work provide theoretical references for the broadband design of anisotropic acousto-optic deflectors.

A numerical simulation of the 3^rd-order cascaded Raman fiber laser based on tellurite fiber at 2-5 μm waveband is presented. We investigate the variation of output power, threshold and optical conversion efficiency of the 3^rd-order Stokes wave with several factors as the fiber length, FBG32 reflectivity, fiber attenuation and pump power. It shows that when the fiber length is shorter than 0.5 m, the threshold decreases and the optical conversion efficiency increases with the fiber length increasing. However, when the fiber length is longer than 0.5 m, the variation of threshold and optical conversion efficiency are contrary. The optical conversion efficiency increases first and then decreases with the reflectivity increasing. When the fiber attenuation increases, the threshold increases and optical conversion deceases. The Raman fiber laser can be optimized with the most suitable tellurite fiber length of 0.5-1.0 m and the most reasonable reflectivity of the 3^rd-order Stokes output FBG32 of 10%-20%. We demonstrate numerically that the 3^rd- order Stokes wave can reach the maximum average power of 45.2 W and the maximum optical conversion efficiency of 45.2% corresponding to the FBG32 reflectivity of 10% and the tellurite fiber length of 0.3 m with the attenuation of 0.85 dB/m, when pumped by 2 μm light with the average power of 100 W. Our simulated results provide a valuable theoretical guidance for the design and experiment of tellurite Raman fiber laser at mid-infrared waveband.

Impact ionization in charge layer and multiplication layer of InAlAs/InGaAs avalanche photodiodes (APDs) with separated absorption, grading, charge and multiplication structures has been studied by two-dimensional simulations using Silvaco TCAD. Special attention has been paid to the charge layer and multiplication layer with different thicknesses and doping concentrations in order to optimize the structure for low band discontinuities and an appropriate electric field distribution. Band-edge profile calculations as well as current–voltage characteristic and electric field results of the APDs will be discussed in this article.

The effect of current mismatch on IV performance of photovoltaic (PV) module is analyzed. Based on the current mismatch theory of solar cell and the series and parallel relation of each cell in the photovoltaic module, the influence analysis program of the current mismatch caused by the irradiance non-uniformity and the response difference of the solar cells in the PV module is established. The experimental and theoretical verification of the IV curve and the PV curve of a photovoltaic module under different shielding conditions have been carried out. It is found that the theoretical results are in good agreement with the experimental results. The influence of irradiance non-uniformity on the measurement of optoelectronic parameters of photovoltaic modules under the conditions of different position of reference solar cell is analyzed. Through theoretical calculation, it is found that in order to reduce the influence of the current mismatch of solar cells on the photoelectric performance test of the photovoltaic module, the difference of solar cells in the PV module and the irradiance non-uniformity of the sunlight simulator should both be reduced, and the irradiance intensity at the standard solar cell position should be consistent with the average irradiance intensity of the test area.

In this paper, during InAs/GaAs (001) quantum dot molecular beam epitaxy growth, four-beam pulsed laser-interference was used to in-situ irradiate on the wetting layer with an InAs coverage of 1.1 monolayer. Significant atomic layer removal and periodic nanostructures including nanoholes and nanoislands were obtained. These periodic nanostructures had a significant influence on quantum dot growth. Especially for the structure of nano-island, quantum dots preferentially nucleated at the edges of them. When the nano-island size becomes small enough, ordered quantum dot arrays are directly achieved on smooth GaAs surface with a follow-up InAs deposition accompanied by the disappearance of the nanoislands. This finding provides a potential technique leading to site-controlled and defect-free quantum dot fabrication.