This PDF file contains the front matter associated with SPIE Proceedings Volume 11894, including the Title Page, Copyright information and Table of Contents

Integrated dissipative Kerr soliton optical frequency comb has been recognized as a promising on-chip multi-wavelength laser source for fiber optical communications, as its comb lines possess frequency and phase stability far beyond the independent lasers. In the scenario of coherent optical transmission and interconnect, a highly beneficial but rarely explored target is to re-generate a Kerr soliton microcomb at the receiver side as local oscillators that conserve the frequency and phase property of the incoming data carriers, so that to enable coherent detection with minimized optical and electrical compensations. Also, in the scenarios of all-optical signal regeneration, a multi-wavelength coherent laser array is also needed to provide the coherent pump fields that enable phase-sensitive parametric amplification of the degraded data signals and constitute regenerative phase transfer functions. In this talk, we will introduce our recent experiments that implement re-generation of a Kerr soliton microcomb that faithfully clones the frequency and phase coherence of another microcomb. We show that such coherence-cloned carrier and LO microcombs can greatly facilitate coherent data receiving by making DSP-based compensations for carrier-LO frequency offsets and phase drifts substantially easier, and at most 1000 times more energy-saving, comparing with a system adopting individual laser carriers and LOs. Moreover, we will also discuss that the coherence-cloned Kerr microcombs can be used to implement multi-channel, configurable all-optical signal regeneration in nonlinear silicon waveguide, phase regenerations of two channel BPSK signals are demonstrated with prominent signal quality improvements. Our work reveals that, in addition to providing a multitude of laser tones, regulating the frequency and phase of Kerr soliton microcombs among data transmitters, regenerators, receivers within an optical network can significantly improve the network performance in terms of signal quality, power consumption, and simplicity.

An athermal, fabrication-tolerant and flat-topped 4-channel coarse wavelength-division multiplexing(CWDM) (de)multiplexer based on cascaded Mach-Zehnder interferometers (MZIs) was proposed in this paper. A combination of strip waveguide and slot waveguide is utilized for athermalization and flat-topped transmission. By optimizing the waveguide widths and lengths of two arms in each MZI, the influence of temperature and waveguide broadening can be compensated. The best temperature dependent center wavelength shift of the four channels is about 12 pm/K, and the best waveguide broadening dependent center wavelength shift is about 0.06nm/nm, while the 1- and 3-dB bandwidths are ~14nm and ~19nm with 20nm free spectral range (FSR) and the crosstalk is < −20dB at center wavelength by utilized the power splitters based on the bend directional couplers.

In this report, we summarize our recent achievements in free-space communications in the mid-infrared (MIR) region enabled by directly modulated quantum cascaded laser (QCL) at 4.65 µm (~65 THz). We have experimentally demonstrated a multigigabit free-space transmission link in the lab environment with the QCL operating at room temperature. The QCL chip is mounted on a commercial QCL mount with a water-cooled Peltier element. Multilevel modulation formats at different baud rates are generated and combined with the laser driving current at a custom-made bias-tee to drive and modulate the QCL. A commercial mercury cadmium telluride (MCT, HgCdTe) photovoltaic (PV) MIR detector with a built-in trans-impedance amplifier was used to receive the MIR free-space signal. With the receiver to be the bottleneck of the system bandwidth, the end-to-end 3-dB bandwidth was measured to be around 320 MHz, and the 6-dB bandwidth was around 450 MHz. We have successfully demonstrated up to 6 Gbps free space transmission with multilevel modulation formats, assisted with effective digital equalization techniques despite the limited bandwidth.

High-accuracy measurement of optical fiber transfer delay (OFTD) is essential to applications such as distributed optical fiber sensing, radio over fiber networks, and optically controlled phased array radars. However, it is difficult to simultaneously acquire high accuracy and high spatial resolution transfer delay distributed in different positions along the optical fiber path. Here, we propose an approach to measure the distributed OFTD based on optical stepped frequency chirp signal (OSFC) enabling sub-millimeter-level spatial resolution and sub-picosecond-level accuracy. Thanks to an optical frequency shifting loop, an OSFC signal with ultra-wide bandwidth of up to hundreds of GHz can be obtained. By coherent de-chirping and fusing the OSFC signal, high-accuracy and high-spatial-resolution distributed OFTD measurement can be achieved. In a proof-of-concept experiment, an OSFC signal with a bandwidth of up to 320 GHz was generated, achieving 0.29-mm spatial resolution and ±0.05 ps accuracy distributed OFTD measurement.

By converting light from localized energy to freely propagating radiation, optical antennas are used for optical trapping and particle manipulation. Based on the optical antenna composed of etched trenches on a waveguide, we propose two integrated waveguide-based optical tweezers for the first time for trapping micro- and nano-particles. A quasi-Gaussian beam and a quasi-spherical-wave field well above the antenna are produced and the optical trapping of the microparticle and nanoparticle is demonstrated. The corresponding upward beams generate gradient forces up to hundreds of pN/W, which is enough to trap particles in microscale and nanoscale effectively. Particles well above the antennas, as high as about 18 μm, can be trapped. This new type of optical tweezers based on photonic antennas is believed to pave the way to build fully integrated photonic circuits with large-scale parallel particle manipulation.

Solution-processed metal halide perovskite light-emitting diodes (Pe-LEDs) show great promise in a range of optoelectronic applications. However, these devices can be limited by poor interfaces to the perovskite films due to poor crystallization control during film processing caused by de-wetting from the bottom layer. The deep (Highest Occupied Molecular Orbital) HOMO levels of the emitters also lead to large charge injection barriers for standard electrodes. To improve this, we develop and report on a small molecule, BPS2, based on phenothiazine-benzimidazole with Lewis base sites. This promising interfacial material is then applied to blue PeLEDs where the energy band alignment of BPS2 to the blue perovskite emitter helps to reduce the hole-injection barrier while blocking electrons. BPS2 can be solution-processed with non-chlorinated organic solvents and provides improved wettability towards perovskite precursor solutions compared to conventional PEDOT:PSS hole transport films. A thin interlayer of BPS2 introduced between PEDOT:PSS and a perovskite emission layer is shown to improve both the device external quantum efficiency and luminance in comparison to the reference device without the interlayer.

Ring resonators and Mach-Zehnder interference structures are promising candidates for compact optical filters and electro-optic modulators in the field of integrated photonics. Two types of ring-loaded Mach-Zehnder interferometers (MZIs) based on 3D direct laser writing are designed by finite-element simulation software. The model is composed of two Y-waveguides, Mach-Zehnder waveguide arm, and a micro-ring coupled with Mach-Zehnder waveguide arm side. The optimal radius of curvature of the two models and the spectral characteristics of the two models are calculated by numerical analysis. The optimal radii of curvature for the bend of Y-waveguides are 385 μm, the average free spectral ranges (FSRs) of are about 18 nm, and the average full widths at half maximum (FWHM) are about 1.4 nm and 3.2 nm, respectively, for the two MZI models. The numerical analysis results have practical reference value for the fabrication of resonator coupled Mach-Zehnder interferometer using 3D direct laser writing technology.

In order to solve the problem of joint resource management algorithm of visible light communication (VLC) and WiFi heterogeneous network, this paper studies different resource scheduling algorithms, and finally chooses improved proportional fair (PF) algorithm to improve the system in different regions of the user access to resources, and optimize the utilization of resources. The simulation results show that the optimized scheduling algorithm can improve the system throughput, fairness and access delay probability (ADP).

Chaotic fiber ring lasers (CFRLs) can be regarded as a type of complex multi-longitudinal-mode (MLM) lasers in optical frequency domain. However, most experimental investigations on laser chaos generation are only restricted to measurements of total intensity dynamics, with frequency-domain longitudinal mode information neglected. In this work, we experimentally study the longitudinal mode dynamics of a CFRL with pump modulation by utilizing a heterodyne detection scheme, in which a beat signal between the chaotic laser and a reference laser is generated. High-resolution instantaneous emission spectra reflecting the fine longitudinal-mode structure of the CFRL in overall are measured through heterodyne detection. Besides, longitudinal mode frequency and intensity dynamics of the CFRL are monitored simultaneously via time-frequency analysis and discussed in detail. Experimental results show that the CFRL exhibits dense and irregular MLM oscillation all the time when operating at intensity chaos state. Meanwhile, each oscillating longitudinal mode in the CFRL is broadened in spectral line due to pump modulation, and can perform chaotic or random-like behaviors in mode intensity. This work will play a significant role in the further analysis, understanding and application of chaotic fiber ring lasers.

Resource allocation management is the key issue to improve the performance of visible light communication (VLC) / WiFi hybrid network. This paper proposes an improved resource allocation algorithm based on proportional fairness (PF) algorithm. Its main idea is to compensate users, and then establish a VLC / WiFi hybrid network model to simulate the traditional algorithm and the improved algorithm respectively, It is verified that the improved algorithm has better fairness and higher throughput than the traditional algorithm.

With an interval which between the elements as the initial amount, the form of motion of the elements is used as the free amount, and the distribution of the optical focal length and the form of the element motion can be obtained by calculating the equation sets. With the global method, the desired results have been achieved.

Integrated optical amplifiers and light sources are of great significance for photonic integrated circuits (PICs) and have attracted many research interests. Doping rare-earth ions in materials as a solution to realize efficient optical amplifiers and lasing has been investigated a lot. We investigated the erbium-doped lithium niobate on insulator (LNOI). Here, we fabricated a 1-mol% erbium-doped LNOI microdisk with a high-quality factor. C-band laser emission at ∼1530 and ∼1560 nm (linewidth 0.12 nm) from the high-Q erbium-doped LNOI microdisk was demonstrated with 974- and 1460-nm pumping. What’s more, spiral waveguide amplifiers were also fabricated by the CMOS-compatible technique. A maximum internal net gain of 8.3 dB at 1530 nm indicating a net gain per unit length of 15.6 dB/cm with a compact spiral waveguide of 5.3 mm length and ~0.06 mm2 footprint was demonstrated.

In the heterogeneous network of visible light communication and WiFi, the fairness index of users is a key index when allocating resource bandwidth. In order to improve the fairness of the system, the average request rate of users and the distance from the wireless access point are mainly considered, and a new weight-based multi-team resource allocation algorithm is proposed to judge the priority of users based on these two indexes. First, the request rates of users are ranked in order, and the first and last two users are formed into a queue, and the first allocation is made according to the weight of the queue, and then the second allocation is made according to the respective weights of the users in the queue. The simulation results show that the fairness index is improved and the improved algorithm can be applied to resource allocation in heterogeneous networks.

The increasing demand of mobile network communication bandwidth requires more information in the limited bandwidth. In this paper, a novel bidirectional transmission system architecture based on RoF-PON system and PWoF system is proposed, and the transmission performance of the hybrid system is simulated. In RoF-based mobile networks, the use of PWoF realizes the centralize power in CO, providing a more cost effective installation method for communication networks, as well as ease of operation and maintenance. The simulation results of the system verify the reliability and feasibility of the system, which proves that the hybrid transmission system of PWoF and RoF-PON can realize the bidirectional transmission of energy and wireless signals.

Recently, near-field optical tweezers integrated on a chip based on silicon on insulator (SOI) have attracted more attention and are promising for biological and chemical analyses. Here we propose a low-loss tapered Si waveguide with a high intensity gradient in the electric field to trap microparticles whose diameters vary from 1 μm to 5 μm. The high transmittance allows for cascading the traps along the direction of light propagation. Optical forces in all three dimensions are analyzed around a high-stiffness potential well obtained.

In this paper, an injection-locked optoelectronic oscillator (OEO) based on frequency conversion filtering process is proposed and experimentally demonstrated. The kernel of the proposed scheme is that injection locking technique is employed to obtain a high side-mode suppression ratio, while the delay-matched frequency conversion filtering process is used to eliminate the phase noise influence of the local oscillation (LO) signal. In the proof-of-concept experiment, a single-mode oscillation at 10 GHz is realized, where the frequency of the LO signal was set to be 10.07 GHz and an intermediate frequency bandpass filter with a center frequency of 70 MHz and a 3-dB bandwidth of 50 kHz is employed. The side-mode suppression ratio and the phase noise are measured to be 76 dB and -123.5dBc/Hz@10kHz, respectively

In order to meet the high bandwidth requirements of next generation access network, this paper combine the advantages of radio over fiber (RoF) and wavelength division multiplexing passive optical network (WDM-PON), and propose the RoF-WDM-PON system architecture. MZM modulation technology is adopted to realize the signal transmission from the center station to the base station, which can meet the demand of high bandwidth and realize the low loss transmission of 20km in the meantime. Simulation results verify the effectiveness and reliability of the proposed scheme.

We proposed a reconfigurable all-optical logic gate (AND, OR) based on a vertical-cavity surface-emitting laser with saturated absorber (VCSEL-SA) subject to dual pulse injection and numerically investigated the effects of injection delay, injection strength and bias current on the system performance. The results show that, through adjusting bias current, the pulse injection strength and the injection delay between two pulses, the reconfigurable all-optical logic gate (AND, OR) can be realized. For a suitable injection intensity, all-optical logic AND and OR gates can be implemented within a certain bias current range. Moreover, both AND and OR gates have good robust to noise under suitable injection strength. These results are expected to open a new window for future ultra-fast neuromorphic computing systems to solve complex classification and decision-making tasks

To design a silicon PIN cavity for ns-tunable lasers, the thermo-optic effect associated with electro-optic tuning is investigated and observed in the relationship of ∆neff and voltage. The thermo-optic effect in PIN waveguide will degrade the performance of the external cavity. We propose optimization strategy to avoid such effect and verified by experiment. Finally, we measured the switching speed of tunable micro-ring within 5ns.

As one of the fundamental phenomena in optics, reflection always occurs for the refractive index contrast between different materials for the impedance mismatch. In many applications, such as solar cells or photodetectors, reflection is unwanted and the reduction of reflection is highly desirable. Metasurfaces have attracted intensive attention recently for their ability to efficiently reshape electromagnetic waves in desired manners on a flat and ultrathin platform. Numerous new concepts, effects, and applications have been intensely studied in recent years. As some of the most important applications, metasurfaces exhibit superior capabilities to enhance absorption, antireflection, and transmission. Here we demonstrate a silicon metasurface with significantly enhanced antireflection over a broad spectrum from 1 to 5 μm. Over the more than two-octaves bandwidth, the transmittance is all above 78% with an average value as high as 95%. The proposed metasurface is a silicon layer on top of an InAs layer on a GaSb substrate and exhibits polarization-insensitive transmission enhancement for the symmetry of the geometry. This structure can be potentially used for thermal targets detection, imaging, sensing, and biochemical analyses.

Optical neural networks (ONNs), a kind of neural network implemented by optical hardware, have attracted more and more attention due to their excellent performance. As a part of ONNs, nonlinear activation functions the key for ONN to achieve more various functions. The realization of nonlinear activation functions by optical hardware has become a research hotspot. Here, we propose and demonstrate an all-optical implementation of a nonlinear activation function, which utilizes the intrinsic absorption and the plasma dispersion effect of germanium at 1550nm. The one has a loss about 4db and a threshold power of 5.1mW, while the another has a loss around 11db and a threshold power of 56.2mW. This proves that our scheme has great potential for nonlinear activation functions.

The intrinsic mechanism of absorbing photons in superconductors reveals the interaction between photons and Cooper pairs, which is of great significance for developing new superconducting nanowire single photon detectors (SNSPDs). Here we propose a photon-assisted phase slip model to describe the interaction mechanism between photons and superconductors. In this model, incident photons destroy large quantities of Cooper pairs and reduce the free-energy barrier of the phase slip, resulting in proliferation in the phase slip events and leading to superconducting transition. The switching rates from the superconducting state of a niobium nitride nanowire under various photon irradiation and temperatures are calculated through the distribution of switching currents in the experiment. The experimental data can be well fitted by our deduced expression of phase slip rate after eliminating the influence of external noise.

Spectral analysis is one of the most widely used analytical tools in scientific research and industry. Computational spectrometers can offer high performance within an ultra-compact footprint and have drawn numerous research interests. Previously demonstrated computational spectrometers typically consist of separate power-splitting components and spectral sampling components, which limit further reduction of the footprint. Here we prose a structure called random medium that combines the power-splitting function and spectral sampling function in the same component, which effectively reduces the footprint of the spectrometer and improve its performance at the same time. The simulations show 200 nm operation bandwidth, with 0.5 nm resolution, and a footprint of 0.006 mm² .

Canonical logic units-based programmable logic array (CLUs-PLA) is an important combinational logic device for its flexibility and user-defined feature. All-optical high-speed CLUs-PLA will lay the foundation for future high-speed optical computing and optical logic processing chip. For standard three-input all-optical CLUs-PLA, one nonlinear device can produce only one type of three-input CLU. In this paper, we propose and experimentally demonstrate a scheme that one nonlinear device can produce eight different types of three-input CLUs simultaneously, owing to introducing bidirectional four-wave mixing and wavelength spacing optimization. We obtain error-free performance for all three-input CLUs operations at 40 Gb/s. Comparing to standard three-input all-optical CLUs-PLA, parallel all-optical CLUs-PLA based on our proposed scheme can greatly reduce the number of nonlinear devices and simplify the computing system.

Gallium nitride (GaN) -based light-emitting diodes (LEDs) have been widely used in lighting, display, communication and other fields due to their high brightness, high luminous efficiency and low power consumption. Polarized LEDs have important potential application in flat panel display, holographic display and imaging fields. It’s very important to study how to realize efficient polarized LEDs. Realizing directional radiation (collimation) is one of the effective methods to improve the utilization efficiency of polarized light. In this paper, we proposed an all-dielectric (Al2O3/SiO2) films/(TiO2) grating nanostructures, and found that the enhanced emission of the polarized LED can be controlled within a specific angle by optimizing the parameters of the all-dielectric nanostructures. In particular, the simulation results show that the angular emission of polarized blue LEDs can be controlled within 11°, and the light output efficiency is more than 60% when the nanostructure is set as: Al2O3/SiO2 film thickness 70 nm, grating period 500 nm, line width 180 nm, and depth 100 nm. The peak light intensity is 5.2 times that of the bare LED. This nanostructure can be prepared easily and it has a large process tolerance. Our findings will provide the feasibility for achieving efficient polarized LEDs in display technology and imaging fields.

A complementary coplanar interdigital electrode photoconductive switch based on vanadium-nitrogen doped 4H-SiC bulk material was developed. The test results show that the combination of vanadium doping and coplanar interdigital electrode structure, the voltage capability of 4H-SiC photoconductive switch is significantly improved and the conductive resistance of 4H-SiC photoconductive switch under low light intensity is reduced. The bias voltage of 4H-SiC photoconductive switch is 10kV. The conductive resistance of 4H-SiC photoconductive switch excited by 0.4mJ 532nm laser is 50Ω. In a 50 Ω microwave system, the peak power output by the load is 0.5MW. By continuously increasing the injected laser energy to 2mj, the on resistance can be reduced to 6 Ω. The results show that the developed vanadium-nitrogen doped 4H-SiC photoconductive switch has the characteristics of stable output waveform, small jitter and high power. The developed vanadium-nitrogen doped 4H-SiC photoconductive switch has certain application value.

Dissipative Kerr solitons generated in microresonators driven by a continuous wave pump laser have promise for widespread applications in spectroscopy and telecommunications. From the perspective of basic physics research, DKSs exhibit rich nonlinear phenomena and serve as a unique platform to study nonlinear physics. In this paper, an optimized all-optical radio frequency (RF) spectrum analyzer, also named frequency domain light intensity spectrum analyzer (f-LISA), is used to characterize the various stable soliton states. Results show that the optimized f-LISA achieves a measurement bandwidth of 2.2 THz and a frame rate of 20.62 MHz. Therefore, the versatile RF spectral patterns of stable two-soliton states have successfully recorded by f-LISA. More importantly, the relative azimuthal angles between two solitons within the round-trip can be extracted by applying an inverse Fourier transform to the RF spectra, indicating that the ultra-fast and broadband RF spectral measurement enable the visualization of soliton motion. It is believed that the f-LISA can function as a powerful and useful tool to monitor the rich nonlinear dynamical phenomena such as soliton number switching in the microresonators

Terahertz polarization control has a wide range of applications in imaging, communication, biology, and analytical chemistry. Polarization rotator is of great significance as one of the main units of a polarization controller. In this paper, we propose and simulate a terahertz polarization rotator based on silicon asymmetrical structure, whose polarization extinction ratio reaches up to 35 dB and 26 dB for transverse electronic and transverse magnetic modes, respectively. Its 15-dB bandwidth is 40 GHz for a conversion length of 4.4 mm. The results show that the integrated scheme can achieve the function of polarization rotation with high conversion efficiency. We believe it will play an important role in terahertz polarization management.

ere we report a high-sensitive Bloch surface wave sensor by integrating a graphene metasurface and a truncated one dimensional (1D) photonic crystal (PC) multilayer structure. The device is configured to be able to excite BSW mode accompanied with a sharp resonance dip, aiming at greatly enhanced sensing performance of the device structure. The sensing capability of the proposed sensor device is theoretically evaluated by investigating the excited mode properties. The result shows that the graphene metasurface coated Bloch surface wave sensor can reach superior detection sensitivity, thus could offer an obvious promotion for improving the performance of Bloch surface wave based sensing applications.

Deep Neural Network (DNN) assisted activity monitoring algorithms are investigated, aiming to discriminate three activity states, including presence without movement, nobody in bed, and presence with movement. The signal is collected from a fiber-based Mach-Zehnder Interferometer (MZI) sensor, which is placed under a 20-cm thick mattress. When people are lying on the mattress, cardiopulmonary activities will lead to the change of the phase difference of the MZI optical fiber sensor. In this paper, three kinds of DNNs are developed to investigate the classification performance, including feedforward neural network (FNN), convolutional neural network (CNN), and long short-term memory network (LSTM). The accuracy of FNN, CNN and LSTM is 95.14%, 99.01%, and 99.37% within one second, respectively. Moreover, LSTM has low time and space complexity and better performance. The algorithms constructed can obtain high accuracy and robustness with low computational overhead and storage consumption and have broad application prospects. What’s more, the MZI optical fiber sensor has many advantages such as low cost and anti-electromagnetic interference, which means that the system can be popular in medical treatment and households.

Real-time SAHS events detection system during sleep is proposed and investigated based on contact-free Mach-Zehnder Interferometer ballistocardiograph (MZI-BCG) senor, which is placed under the mattress. The breath activity influences the optical phase difference of the MZI which is demodulated with 3*3 optical coupler. In this paper, three SAHS events are successfully detected, including OSAS (Obstructive sleep apnea syndrome), CSAS (Central sleep apnea syndrome) and MSAS (Mixed sleep apnea syndrome). The proposed system is simple, cost-effective and non-invasive, which has great potential application in home monitoring

A higher sensitive sensor can provide more precise measurements in industry and research applications. Sagnac loop structure is a significant interference structure in optic fiber sensors for strain measurement. In this research, we propose a sensor structure that links a commercial Panda PMF to a 4° TFBG. With an analysis of the sensitization effect of TFBG to the interference sensors, there will be a significant enhancement of sensitivity. Based on the analysis, we demonstrate a sensor that combined TFBG with PMF to enhance the sensitivity. When a strain affects the sensor, the spectra will shift towards a longer wavelength direction. When a strain affects the sensor, the spectra will shift towards a longer wavelength direction. The proposed sensor can provide a sensitivity up to 51.9pm/ffff and 50.5pm/ffff. Meanwhile, it can measure the temperature independently on a sensitivity of 8.56pm/℃

Terahertz quantum cascade lasers (THz QCLs) in metal-metal (MM) ridge waveguides have been fabricated and hetero bonded on aluminum nitride (AlN) substrate as heat sink submount. Compared with the conventional structure of THz QCLs in MM waveguides on gallium arsenide (GaAs) as receptor substrate, AlN performs superior heat dissipation properties for thermal management due to its much higher thermal conductivity. The light–current density–voltage (L-J-V) characterization shows comparable maximum operating temperature (Tmax) at 93-95 K for both THz QCLs bonded on AlN and GaAs under short pulse injection (250 ns). However, as the injected pulse duration increases for THz QCLs on GaAs, the light intensity drops quickly, eventually leading to lasing quenching when the pulse duration is above 30 µs at 80 K (heat sink temperature). On the other hand, THz QCL on AlN shows much stronger light intensity and slower decrease with the increase of the pulse duration; for example, the light intensity is 100 times higher for the THz QCL on AlN (pulse duration of 40 µs) than THz QCL on GaAs (pulse duration of 30 µs) at the same measurement conditions at 80 K. This study shows suspected joule heating plays a great role on THz QCLs operating from long duty cycle towards continuous-wave (CW) mode, indicating AlN substrate as a high thermal conductivity material produces superior thermal management for heat extraction and dissipation.

In this article, efficiency performance of blue GaN/InGaN micro light emitting diodes (μ-LEDs) are investigated as functions of chip sizes, quantum barrier doping level and the number of quantum wells (QWs) by simulation. Internal quantum efficiency (IQE) and external quantum efficiency (EQE) drastically decrease with decreasing mesa sizes of μ-LEDs. The simulation indicates that μ-LEDs with n-doped quantum barriers can effectively suppress the Shockley-Read-Hall (SRH) nonradiative recombination and improve the efficiency compared to those with intrinsic quantum barriers in small μ-LEDs. The simulated results also show that decreasing the number of QWs can improve the IQE of μ-LEDs with higher radiative recombination rate in a single QW. An optimized design for 5×5 μm² GaN/InGaN μ-LEDs with n-doped barriers and a single QW shows around 367% efficiency improvement at 1 A/cm² comparing to the conventional intrinsic multiple QWs-based design in simulation.

Two-dimensional modeling of the InP/InGaAsP modified uni-traveling carrier photodiodes is reported. Basic device characteristics like dark I-V curve, device capacitance effect, frequency response and bandwidth etc., are presented. The simulation shows high bandwidth comparable with the experimental report. The results are further discussed with respect to the cliff layer dopant density