This PDF file contains the front matter associated with SPIE Proceedings Volume 10812, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

High-contrast metastructures like one-dimensional high-contrast gratings (HCGs) are promising to improve the performance of conventional VCSELs, also presenting a basis for new applications. Different from the previous studies where HCGs are always modelled being of infinite size, we studied here the finite-size HCGs, which match the real situation. We observe finite-size HCGs behaving very differently from infinite-size HCGs. The reflectivity of a finitesize HCG strongly depends on the HCG size and the source size. At the same time, the simulation results show, that finite-size HCGs can shape the output beam, and a Gaussian-like reflected wave is typically achieved. Most important the normally incident light is partly redirected to the in-plane direction, showing unidirectional transmission. Monolithically integrated HCG-based optical sensors can be based on this novel effect. An integrable HCG reflector was fabricated with GaInP as the sacrificial layer targeting the application of HCG-VCSEL at 980 nm range. The measured reflectivity agrees well with the calculated reflectivity.

To establish highly performing vertical cavity surface-emitting lasers (VCSELs), it is essential to have an adequate understanding of the intrinsic laser dynamics of these devices. However, this is done while bearing in mind that extrinsic parasitic elements in VCSELs play an important role in limiting the intrinsic modulation bandwidth. Compared to largesignal analyses, the small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. An alternative approach to that of using the rate equations is to transform theses rate equations to an equivalent circuit model. In this work, we firstly present advanced electrical circuit modeling of the intrinsic dynamic performance of multi-mode VCSELs, for the case where lasing modes do not share a common carrier reservoir. The electrical circuit model is derived from innovative advanced multi-mode rate equations that take into account the effect of spatial hole burning, gain compression, and inhomogeneity in the injection current. Secondly, we analyse different electrical parasitic equivalent circuit models in the aim of comparing them and selecting the one that can best describe and represent the physical properties of our high-performance VCSELs. Through measuring the microwave reflection coefficient S₁₁(f) and fitting it into the calculated counterpart from the equivalent-circuit impedance model, the parasitic components of the equivalent circuit model are extracted.

In this paper, the optical problem of the Vertical Cavity Surface Emitting Laser (VCSEL) is analyzed in details. Taking advantage of the VCSEL layer structure, Maxwell’s equation is discretized on uniform Yee grid, and the rigorous full vectorial Finite Difference Frequency Domain (FDFD) method was used to formulate and solve the complex eigenvalue problem. The full vectorial solver is well suited for the fundamental as well as the higher-order modes and includes different field polarization. The method is demonstrated for advanced VCSEL incorporating the surface reliefs and the oxide layer. In order to compare with the experimental structure, a superposition of the VCSEL modes is used to construct the Linearly Polarized (LP) mode.

We theoretically investigate the propagation characteristics of inhibited spiking dynamics between two unidirectionally coupled VCSEL-based photonic neurons. The results show that, the inhibition of spiking regimes in a transmitter VCSEL (T-VCSEL), in response to the arrival of external perturbation, can be propagated to another receiver VCSEL (R-VCSEL) and two VCSEL-based photonic neurons have similar responses to the external perturbation. With increasing perturbation strength, the spikes with higher amplitude and lower oscillation frequency can be observed during the perturbation time. The spikes can be entirely suppressed for enough perturbation strength. Additionally, the spiking inhibition window can be controlled through adjusting perturbation duration.

When a light is properly injected to a semiconductor laser (SL), periodic one (P1) dynamics can be excited and a microwave signal with a specific frequency can be generated after optical-to-electrical conversion. By varying the injection strength, the detuning frequency, or both, a continuously tunable microwave signal over a frequency range up to 100 GHz can be generated. Based on this principle, we implemented wideband linear frequency modulation (LFM) signal generation, which is highly required in high-resolution radars. While, this method suffers from a poor spectrum purity of the generated LFM signal, because the generated microwave using optically injected SL has a relatively large 3-dB linewidth on the order of megahertz. To overcome this problem, we applied a feedback to the optically injected SL with the round-trip time delay matched to the period of sweeping frequency, through which the spectrum purity of the obtained wideband LFM signals is greatly improve. Applying the generated broadband LFM signals, high-resolution radar target detection is demonstrated, which shows the good potential of the proposed wideband LFM signal generator in practical applications.

Optoelectronic oscillator (OEO) has been considered as the best technique to produce microwave signal with low phase noise. However, due to the electronic bottleneck rooted from frequency selection mechanism based on electrical filter, it is faced with such a dilemma that it is difficult to simultaneously obtain microwave source with broadband tunability and better phase noise performance. Semiconductor laser under optical injection has showed rich nonlinear dynamics and has demonstrated their potential in various domains, such as information encryption and all-optical signal processing. In this paper we propose and investigate a new modulator-free OEO scheme based on an optically injected semiconductor laser with the subharmonic modulation. The performance of the proposed OEO is optimized with respect to the single sideband phase noise, and the tunability of the generated microwave signal is discussed. A generated microwave signal at 11.42 GHz is experimentally demonstrated with the single sideband phase noise of -101.21 dBc/Hz at the offset frequency of 10 kHz.

The accuracy of the detection in the image-based subgrade settlement monitoring system depend on the quality of the collected spot image, This paper studies the main factors affecting the quality of spot images and propose a method for quality assessment of spot image without reference. The method analyze the characteristics of the spot change under the influence of external conditions, and reflect the change effect of the spot feature through the size, brightness, edge definition and contrast of the spot image.Then,the four evaluation factors are integrated into one. Through the experiment, the spot images under the influence of the target surface are collected. The spot image obtained by the experiment is evaluated using the non-reference spot image evaluation method proposed in this paper, and verifies by measuring the center position of the spot image. The experimental results show that the spot image is affected by different influencing factors, this evaluation method method can combine various influencing factors to reflect the change of image quality,and can give reasonable evaluation results for spot images that are affected to varying degrees. It provides theoretical and experimental basis for the actual subgrade surface settlement monitoring system.

In conventional chaos communication systems based on external-cavity semiconductor lasers (ECSLs), messages are embedded into the chaotic carriers and then directly transmitted to the receiver for recovery. Since the modulated chaotic carrier (chaos + message) is directly transmitted in public link, the eavesdropper can easily access it for interception. It has been proved that when the bit rate is relatively low, the message hidden in the chaotic carrier can be intercepted by using a linear filter with a proper cutoff frequency or reconstructing an illegal receiver system based on the injectionlocking effect. We propose and numerically demonstrate a security-enhanced chaos communication system by introducing an optical time-frequency encryption (OTFE) module to convert the modulated chaotic carrier (chaos + message) as an uncorrelated signal before transmission. At the receiver end, a matching optical time-frequency decryption (OTFD) module is adopted to recover the modulated chaotic carrier for the final message recovery. The results demonstrate that, with the OTFE module the modulated chaotic carrier would be transformed as an uncorrelated chaotic carrier with the time delay signature being perfectly suppressed in the time domain. Simultaneously, in the frequency domain, the spectrum of chaotic carrier would be flattened, and the efficient bandwidth of chaotic carrier can be expanded by several times. With respect to conventional chaos communication systems, the proposed scheme shows obviously higher security under the attack scenarios of direct linear filtering and synchronization utilization. The proposed scheme provides a novel way to implement high-security chaos communication.

A scheme for generating frequency-modulated continuous-wave (FMCW) based on an optically injected semiconductor laser (SL) is proposed and demonstrated experimentally. A modulated light injection drives an SL into period-one (P1) state with modulated microwave frequency for generating FMCW, and then an optical feedback is introduced to further enhance the frequency comb contrast of the generated FMCW. Under proper operation conditions, a FMCW signal with a sweep range of 11.39 GHz (10.08 GHz-21.47 GHz) and a sweep rate of 0.72 GHz/ns is obtained, and the frequency comb contrast is increased by 20 dB after introducing the suitable optical feedback.

A novel optical spectrum compression scheme based on time-dependent filtering is proposed and demonstrated. The spectrum compression is realized by using nonlinear polarization rotation effect to achieve power-dependent filtering of a chirped soliton pulse. In the experiment, a single-stage spectrum compression unit based on the proposed scheme is employed in the soliton self-frequency shift-based optical quantization system to improve the quantization resolution. The experimental results show that an average output spectrum width of 1.5 nm is obtained using the proposed scheme, which is 68% of that using the traditional comb-like fiber scheme. In addition, the quantization resolution using the proposed scheme is 5.1 bits, which is 0.6 bit higher than that using a single-stage spectrum compression unit based on the traditional comb-like fiber structure.

Under suitable filtered optical feedback, a weak-resonant cavity Fabray-Perot laser diode (WRC-FPLD) is rendered into chaotic state, and the central wavelength of chaotic output can be tuned through varying the central wavelength of filter. The output chaotic signal with wavelength-tunability is unidirectionally injected into another WRC-FPLD and drives it into chaotic state, and then wavelength-tunability chaos synchronization can be realized. The experimental results demonstrate that, under suitable injection strength and frequency detuning, chaos synchronization between two unidirectionally coupled WRC-FPLDs with maximal correlation coefficient about 0.900 can be achieved under different wavelengths.

An electrical method is proposed for the absolute time-delay characterization of optical delay components based on the frequency-shifted self-heterodyning. The method utilizes the electrical spectrum of the heterodyne products between the delayed optical signal and the frequency-shifted optical carrier, and achieves the intrinsic absolute time-delay measurement from the notch frequencies of the spectrum at microwave region. Moreover, our method enables highresolution and wide range measurement with low-frequency electrical spectrum analysis. The theoretical analysis is supported by experimental results.

Silicon photonics have been developed very successfully in the past decades. In order to break the limitation of the silicon material for realizing photonic devices, more and more special optical materials are introduced to silicon photonics, and silicon-plus photonics is being developed. In this paper, we give a review on recent progresses of siliconplus photonics for light manipulation and photodetection by introducing metals, germanium, 2D materials, semiconductor nanowires, etc.

We propose and demonstrate a self-calibrating approach to measure the magnitude response of a broadband electro-optic intensity modulator based on photonic downconversion sampling. A low-repetition-rate mode-locked laser is employed to sample a swept-frequency microwave signal via the modulator under test, where the magnitude response of the modulator is calculated from the relative intensity of the Fourier frequency components in the first Nyquist frequency range and the direct current. In the experiment, magnitude response and half-wave voltage versus frequency of a commercial Mach-Zehnder electro-optic modulator within a frequency range of 0-40 GHz is successfully measured using the proposed method.

32-channel hybrid III-V/silicon laser arrays operating at C-band with 100GHz wavelength spacing are designed and simulated. Each channel of the hybrid III-V/silicon laser arrays includes III-V/silicon waveguide gain region with lateral sampled Bragg grating (LSBG) on silicon waveguide for selecting a single longitudinal mode, tapered III-V/silicon waveguide coupling region and silicon waveguide light output region. Light generated by III-V active region evanescently couples to the silicon waveguide, and outputs from the silicon waveguide. The seed grating’s period of LSBG is fixed and varing the sampled grating period of LSBG for selecting wavelength. The transfer matrix method is used to simulate LSBG’s parameters of hybrid III-V/silicon laser arrays. The simulation results show that 32- wavelengths are selected successfully by LSBG when the sampling grating periods are between 4.6 μm and 6.9 μm while the seed grating is fixed at 251 nm. Besides, the tapered III-V/silicon waveguide coupling region is designed and simulated by eigenmode expansion method of commercial software to convert the light spot size and increase the coupling efficiency from III-V to silicon waveguide. By optimizing the parameters, the coupling efficiency is up to 90% while hybrid III-V/silicon tapered waveguide length is fixed at 400μm

Vertical cavity surface emitting laser (VCSEL) and multimode fiber (MMF) based short reach optical solutions are widely deployed as the optical engines in the intra-datacenter communications since its significant advantages of low cost, easy design and test, high yield and low power consumption. With the increasing demand for highspeed interconnects, more than 100-Gb/s per lane and more than 100m transmission distance are highly required in order to meet future 4×100 Gb/s and 800G/1T module deployment in the high performance computing systems including datacenters and supercomputers. In this paper, we propose the comprehensive optical and electrical equalization approaches for the bandwidth limited devices, with the typical VCSEL 3-dB bandwidth around 20 GHz, to deal with the challenges including the inherent modal and chromatic dispersion, modulation nonlinearity and various noises in order that multimode interconnect could reach 100 Gb/s/lane over the distance more than 100m. To mitigate the various noises due to the multimode nature of the interconnect solutions, we propose the spatial phase manipulation scheme to dynamically control the coupling coefficients between the VCSEL and MMF links. We further investigate the physical limitations of the VCSEL during multilevel modulation, and propose the level dependent equalization approaches for the PAM4 modulation. Finally, more advanced nonlinear equalization, Volterra equalization, is investigated and a simplified version named by threshold based pruned retraining Volterra equalization (TRVE) is experimentally demonstrated for the VCSEL enabled 100 Gb/s PAM-4 over 100m MMF. Up to 94.2% and 88.0% complexity reduction has been achieved for B2B and 100m.

We have designed and investigated a stable polarization microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting lasers (VCSELs) at wavelength around 980 nm with an inter-cavity subwavelength grating (ISWG). An ISWG is etched on the top of the “Half-VCSEL” consisting of the active semiconductor and the bottom mirror to select the polarization mode during the whole tuning range. The rigorous coupled wave analysis (RCWA) had be used to design and optimize the parameters of the ISWG including index, thickness, period and duty cycle to achieve a high reflectance for the desire polarization and a lower reflectance for the other polarization. Then we calculated the total reflectance of ISWG, air gap and top DBR using transmission matrix method. By designing the parameters of ISWG, we can ensure that the fundamental mode has a higher reflectance, or lower threshold current than the other modes. After calculation, we have gotten the parameters as follows. The index of the ISWG and the substrate is 3.58; thickness is 300nm; period is 500 nm; duty cycle is 0.5. The reflectance of ISWG is 0.985 for the TM polarization and 0.382 for TE polarization. The total reflectance of the whole structure is 0.995 for TM polarization and 0.902 for TE polarization in the tuning range. The difference of the reflectance between two polarization modes can select the polarization mode of lasing. This structure can achieve a tuning range of 30nm for TM single polarization.

An innovative model to describe the small-signal modulation response of high-speed multi-mode vertical-cavity surfaceemitting lasers (VCSELs) is presented. Using an advanced theoretical approach, multi-mode rate equations for these VCSELs are established. Moreover, in order to characterize the dynamic performance, a comprehensive analytical fitting function based on this novel approach is derived. This allows the extraction of consistently expanded figures of merit for these laser devices. The main concept of our novel approach is based on carrier reservoir splitting. This is a result of numerous effects such as mode competition and spatial hole burning (SHB). Furthermore, compared to other standard approaches, our novel model includes the effects of carrier diffusion, gain compression and inhomogeneous current injection. Beside the traditionally extracted figures of merit, this model gives insight into photon lifetime and the local distribution of the injection current.

Diode Laser wavelength standards at the 1.5 μm optical telecommunication band have important application in the dense wavelength division multiplexing (DWDM). This need motivates the frequency stabilization by Doppler-free spectra of the molecule overtone, such as acetylene ¹³C₂H₂ or ¹²C₂H₂, HCN and ammoni ¹⁴NH₃. Especially, the P(16) line of ¹³C₂H₂ in the (ν1+ν3) band was adopted by the International Committee for Weights and Measures (CIPM) for practical realization of the definition of metre, which was given a uncertainty of 10 kHz with a relative uncertainty of 5×10-11. The recommended stabilized laser has elicited widespread interest in the national metrology institutes (NMIs). In this paper, we demonstrate an initially experimental result of the acetylene ¹³C₂H₂ stabilized laser using the Doppler-free spectra with one-way pump and probe configuration in the external acetylene cell. This stabilized near infrared laser employs a commercial external cavity tunable diode laser with the classic Littman-Metcalf configuration, and it could be applied in the optical fiber communication as a wavelength reference standard. A home-made 3f detection and servo system is taken to lock the external cavity tunable diode laser (ECDL) at the Doppler-free transition of the ¹³C₂H₂ P(16) line with one-way pump and probe configuration. The initial experiment results show that a standard deviation of the frequency fluctuation of 2.7 kHz and a relative stability of 4.2×10^-13 at 100 s are obtained, respectively. In the future, we will focus on the optimization of these systems, including disciplining the acousto-optic shift frequency to an atom clock and optimizing the parameters of the closed loop.

In this work, we theoretically investigate the relative intensity noise (RIN) properties of quantum dot (QD) lasers through a rate equation model including the Langevin noises and the contribution from the off resonance energy levels. It is shown that the carrier noise significantly enhances the RIN which can be further reduced by properly controlling the energy separation between the first excited and the ground states. In addition, simulations also unveil that the RIN of QD lasers is rather temperature independent which is of prime importance for the development of power efficient light sources. Overall, these results indicate that QD lasers are excellent candidates for the realization of ultra-low noise oscillators hence being advantageous for fiber optics communication networks, short reach optical interconnects and integrated photonics systems.

High power water-cooled horizontal array diode lasers are critical components in laser cutting systems for the compact line beam shape. Because of heat spreading effect of heatsink and thermal crosstalk effect among the laser bars, local thermal resistance for each bar is different, leading to unhomogeneous output power for each bar and non-uniform intensity distribution for laser line beam. In this paper, heat transfer and pressure drop as function of water flow rate in a single bent microchannel is firstly studied by computational fluid dynamics. For reaching same local thermal resistance, numerical simulation is used to determine local heat transfer coefficient (HTC) distribution for microchannels within the horizontal array heatsink. The water inlet or outlet structure respectively in the upstream and downstream of distributed channels is designed to compensate the distributed pressure drop so that each flow path from inlet to outlet has same pressure drop. This work gave the basic thermal design rule for horizontal array diode lasers to reach uniform junction temperature.

High spatial coherence can maintain the beam stability of the laser after a long distance. However, it limits the applications in laser display including projection and imaging system, because the high coherence of laser diodes cause the artifacts such as speckle. In this work, we design a novel 6xx nm chaotic cavity laser diode, which consists of a Dshaped section used to achieve a large number of independent spatial modes thus reduce coherence and a stripe area to improve power. The radius of the D-shaped cavity is 500 μm and the length of stripe is 1000 μm. The red laser based on GaAs substrate is fabricated by standard photolithography and reactive ion etching process. To obtain an enough optical confinement by effective refractive index step, the etching depth exceeds the active region. The high-power chaotic cavity low-spatial coherence electrically pumped semiconductor laser is first realized with the wavelength around 630 nm. The spectrum width of 15 nm at full width at half maximum (FWHM) and output power of 300 mW is obtained under pulse operation. The speckle contrast is measured to be 5%, showing great potential of reducing speckle from the source directly for laser display.

A theoretical model is analyzed to evaluate the laser emission efficiency and the ratio of heat generation in the gain medium which are calculated by the output optical laser power vs the amount of absorbed power. During the lasing process, the total of absorbed power in the Nd:YAG crystal is obtained around 5.8-W with the 7.6-W incident power by measuring the thermal cooling power of the gain medium. The slope efficiency of the Nd:YAG NPRO laser is obtained of 78.7% experimentally, which approaches the quantum limit of 79% theoretically. This newly realized feature in the Nd:YAG NPRO laser allows for increased energy efficiency and hence less demanding on the heat management, a feature that is especially relevant to laser power upgrade in the ground-based gravitational wave detectors as well as developing laser sources for space-borne gravitational wave detectors.

Based on the situation that imported low quality level of the semiconductor pump lasers are selected for most China space applications ,via analyzing the basic characters and failure mechanisms, and researching on relative international standards, this paper provides a quality assurance test items and procedures that applies to the imported low quality level semiconductor pump lasers, and introduces techniques and conditions for each tests. It is proved by an actual case that the quality assurance methods this paper provided are effective and feasible, and can be adopted by all the quality assurance for the imported low quality level pump lasers for China space application in the future.

An approach to retrieving intrinsic phase response of optical filters from magnitude response only measurement is proposed and demonstrated. Phase retrieval is based on the fact that the intrinsic phase response of an optical filter with a minimum phase response has a unique relationship with its magnitude response. A phase retrieval algorithm based on fast Fourier transform is proposed. In the experiment, the intrinsic phase response of notch in the reflection spectrum of a phase-shifted fiber Bragg grating is successfully retrieved from the measured magnitude response, which is free of the influence of fiber pigtail in the measurement setup.

We propose a scheme for acquiring dual-channel physical random bits based on a vertical-cavity surface-emitting laser (VCSEL) under dual-path polarization-preserved chaotic optical injection (DP-PPOI). The injection chaotic light is generated by a master VCSEL (M-VCSEL), which is subjected to polarization-preserved optical feedback from a fiber Bragg grating (FBG). Under suitable operation parameters, the outputs of X polarization component (X-PC) and Y polarization component (Y-PC) in the M-VCSEL are chaotic signals with weak time-delay signatures (TDS), which are injected into another VCSEL (named as the slave VCSEL, S-VCSEL) via DP-PPOI. Through selecting the injection parameters, the X-PC and Y-PC in the S-VCSEL can simultaneously output chaotic signals with wide bandwidth and suppressed TDS, which are used as entropy sources for generating dual-channel random bits. The results demonstrate that the rates of generated dual-channel random bits can be up to 500 Gbits/s.

Self-mixing interferometry (SMI) is a well-developed sensing technology. An SMI system can be described using a model derived from the well-known Lang and Kobayashi equations by setting the system operating in stable region. The features of an SMI signal are determined by the external optical feedback factor (denoted by C). Our recent work shows that when the factor C increases to a certain value, e.g. in moderate feedback regime with 1<C<4.6, the SMI system might enter unstable region and the existing SMI model is invalid. In this case, the SMI signals exhibit some novel features and contain higher-frequency components. To detect an SMI signal without distortion or take suitable correction on the SMI signal, it is must to make an analysis on the system bandwidth and its influence on SMI signals. The results in this paper provide useful guidance for developing an SMI sensing system.

When a fraction of external optical feedback re-enters inside cavity of a laser diode (LD), the laser intensity and its wavelength will thus be altered. The LD in this case is often called as a self-mixing laser diode (SMLD). This paper presents an SMLD for profile measurement. The LD is modulated by the injection current in triangular waveform and a target to be measured is installed on a mechanic scanning device. The reflection light by the target contains its surface profile. The profile information is then carried in the laser intensity and can be pickup by a photodiode packaged in the rear of the LD. We call this modulated laser intensity as self-mixing interferometric (SMI) signal. In this paper, a new algorithm is developed to retrieve the profile from the SMI signal. Results show that the proposed design is able to achieve the measurement of profile with high resolution.

Material parameters such as Young’s modulus and internal friction are important for estimation of material performance. This paper presents an experimental study for measuring material related parameters using a selfmixing interferometric (SMI) configuration. An SMI system consists of a laser diode (LD), a lens and an external target to be measured. When a part of the lasing light back-reflected or back-scattered by the external target re-enters the LD internal cavity, both optical frequency and intensity of the lasing light can be modulated. This modulated laser intensity is often referred as SMI signal. Generally, the target related movement or its surface information can be retrieved from this SMI signal. In this paper, an SMI system is implemented. A tested sample is used as the target to form the external cavity of the LD. The tested sample is stimulated in vibration. Continuous wavelet transform (CWT) is utilized to retrieve the vibration information of the tested sample from an SMI signal. We are able to obtain both Young’s modulus and internal friction from a piece of an experimental SMI signal. This work provides a novel, simple non-destructive solution for simultaneous measurement of Young’s modulus and internal friction.

For the subwavelength grating guided mode resonance filter (GMRF) with a spacer layer, the drift mechanism of reflective phase was analyzed, and the relation between the optical wave phase and the spectral linewidth was investigated with the planar waveguide theory and the principle of guided mode resonance. On this basis, the super narrow linewidth resonator with the wavelength of 852 nm is designed. The simulation results show that the larger slope of phase as a function of wavelength (dφ/dΛ) becomes in the resonant range, the narrower linewidth (Δλ) is shown in the reflection spectrum. Furthermore, the energy of electric field concentrated in the waveguide layer is also higher in the corresponding field distribution. Different structural parameters have different effects on reflection characteristics. As the thickness of the grating layer decreases, the slope of the phase (dφ/dλ) increases from 1.0419 to 12.2666, and the linewidth decreases by 90%. With the increase of spacer layer thickness , the phase slope (dφ/dλ) increases from 2.04 to 7.15, and then the Q (Q≈λ0/Δλ) value goes from 1058.382 to 5174.393. The variation of the period of the subwavelength grating mainly affects the location of the resonance center wavelength, but has little effect on the rate of phase swing. By optimizing these parameters, the coupled resonant cavity with a narrow linewidth 0.002nm is designed, and the Q reaches 4.26×10⁵ .

We demonstrate a screening and qualification flow of semiconductor lasers to verify their applicability for aerospace environments. The screening and qualification methods are based on background of standard methods, including Telcordia GR468, IEC 61751, MIL-STD-883 and GSFC. While determining the item of the flow, the failure modes in practical application are also considered. By using of the screening and qualification methods, the quality assurance agency could select the more suitable semiconductor lasers for space flight mission.

Thermal dissipation is critical for any semiconductor lasers, because heat will lead to their performance degradation, such as wavelength shift, output power decrease, and even device damage. For InP-based InGaAsP semiconductor lasers, heat affection induced by their Auger recombination is so strong that thermal-electronic-controller must be adopted for these lasers operation. Therefore, heat dissipation from up (flip-chip method) and down (heat sink) of these InP-based InGaAsP semiconductor laser has been thoroughly investigated. cladded by the passivation material with high thermal resistance. In this paper, we built two-dimension heat dissipation model by finite-element-method for InP-based InGaAsP FP lasers and investigated the influence of lateral waveguide structure, passivation material, and filling material on the lateral heat dissipation. Our simulation results shows that both the passivation material with low thermal resistance and two-channel waveguide filled with high thermal conductivity material indeed benefit the lateral heat dissipation of these edge-emitting semiconductor lasers. The maximum temperature decrease of 6.8°C in this InP-based InGaAsP ridge waveguide laser with the output power of 18 mW has been achieved in the optimized waveguide structure, where, double-channel waveguide with channel radius of 17 μm and filled with graphene was adopted, the active region is cladded by 300 nm-thick AlN, and then the filling layer of graphene is designed near the InP ridge, and a layer of gold coating with 3.5 μm thickness is deposited on the ridge of the semiconductor laser. Such investigation shows that lateral heat dissipation is possible for these channel waveguide semiconductor lasers.

We present monolithic 910-nm high power vertical-cavity surface-emitting laser (VCSEL) module suitable for longdistance LIDAR (Light Detection and Ranging). The 910-nm high-power VCSEL array is finely designed and fabricated. The output power of a single VCSEL array (163 devices) reaches nearly 2 W under QCW operation, without being cooled. Driven by the external current source, the peak output power of a single VCSEL array reaches 25.5 W under pulsed operation with a repetition frequency of 10 kHz and a pulse width of 30 ns. To improve the pusled performance of VCSEL array, the monolithic VCSEL array module with integrated driver is developed. The peak output power of this module reaches nearly 85W. And its optical pulse width is 22 ns only. Thus integrated driver circuits demonstrate much better pulsed properties. The ranging setup is built and the detection distance of more than 20 m is realized. We believe that this monolithic VCSEL array with high power, dense package and superior impulse response has great commercial potential in future applications requiring intelligent driving like LIDAR for automotive.

The optical power supply technology has been presented several years and used in Electric current transformer (ECT). However, the reliability of the technology is proved to be low in actual application, which limit its widely used in electric power industry. In this paper, we propose a novel optical power supply system for Ultra-High Voltage (UHV) Grid, which utilizes 810-nm laser diode in low-voltage (LV) environment and GaAs photocell for power supply in highvoltage (HV) environment. A Lithium battery is further employed in HV environment which makes the power supply scheme more flexible and reliable. In addition, two VCSELs are also used for information transmission between the LV and the HV environment. And the parameters of the system, such as load power, laser driving current, laser temperature, semiconductor chilling plate driving current, ambient temperature and ambient humidity, are collected, transmitted via optical fiber and processed by the power management scheme. The scheme is able to dynamically control the output power of the laser diode according to the load power variance and make the Lithium battery working when the optical power supply is unavailable or burst heavy power supply demand is emerged. In this way, the output power variance of the laser can be kept as low as possible, which effectively increase the reliability of the system.

Aiming at the problem that the target deviation of settlement monitoring system affected the accuracy of settlement monitoring, a monitoring target attitude measurement system was designed to realize the real-time non-contact measurement of target pose. Firstly, the monocular vision and the monitoring target surface were combined, and the perspective projection model of the camera was established according to the known geometric constraint relationship between the two-dimensional feature points of the target surface. Then, for the five feature points arranged in a cross, based on the PnP problem, the HOMO algorithm was used to linearly solve the target pose. Based on this, the pose optimization solution was obtained by the nonlinear L-M algorithm. The system could perform real-time feature point image processing and pose calculation. An experimental platform for simulating the target pose measurement system in the surface settlement monitoring of ballastless track was built. The experimental results showed that the root mean square error of the three angles of the pose measurement system is 0.126°, 0.14°, 0.12°, and the whole identification process takes 1.9s. The measuring system had high calculation accuracy and was used in a short time, which was suitable for the flawless track surface settlement monitoring system.

A tilted wave (TW) laser based on the quasi-periodicity photonic crystal (QPC) structure is studied to improve the maximum power and wall-plug efficiency of laser diodes. In this work, we first use the longitudinal QPC structure instead of the thick passive waveguide compared with previously reported. In order to localize the first order mode, we designed and optimized the longitudinal QPC structure. The optical confinement factor (OCF) of the fundamental mode is only onesixth of the first order mode. In the experiment, a continuous wave power of 12.8 W at 980 nm is achieved with a peak power conversion efficiency of 57.2%. The laser emitted two nearly symmetric narrow vertical beams in far field pattern, which has a full width at half maximum (FWHM) of 7.6° each.

The band structure of InGaAs strained quantum wells are investigated using 8×8 Luttinger-Kohn Hamiltonian including conduction band, heavy hole, light hole, spin-orbit splitting and strain effects. The energy dispersion curves of conduction band and valence band, the material gain spectra of TE and TM mode are given, respectively. The variation of peak gain with carrier density, temperature, well width, and Indium composition of InGaAs are calculated. The calculations show that the higher the In composition of InGaAs and the thicker the well, the longer the emitting wavelength are. The higher carrier density and higher In composition lead to the higher peak gain.

At present, the optical fiber sensor generally conducts single parameter characterization, but for the power transmission line monitoring, multi-parameter sensing is needed, such as to monitor the line temperature, humidity, tower tilt, line breeze vibration, and so on. However, to realize multi-parameter sensing, many different sensors and information demodulation devices are needed, which is so expensive that it makes the optical fiber sensor cannot be used in the power industry. In particular, the performance of the equipment is greatly decided by the performance of key devices such as lasers, electro-optical modulators, photodetectors, and spectral demodulation components. So, in our work, the InP-based tunable DBR lasers with narrow linewidth, InP-based electro-absorption modulators (EAM), and monolithically integrated opto-electronic circuits based on InP integration platform are studied to satisfy the requirement for optical fiber sensing system. The distributed Bragg reflector (DBR) laser obtained is within C band, and hop free, and the wavelength tunable range is larger than 15nm with laser linewidth less than 500kHz. And by changing the diode temperature or driving current, the output light wavelength can correspondingly change. For the EAM, the pulse extinction ratio is greater than 10dB, and the rising time is less than 20ps, and the insertion loss is less than 6dB. These devices can be used in distributed optical fiber sensing systems, fiber Bragg grating sensors and tunable diode laser absorption spectroscopy apparatuses, and so on.