In fiber Brillouin sensing, the problem of ambiguous judgment caused by intrinsic cross between the temperature and the strain has always been a research hot topic in the field of distributed optical fiber sensing. In response to this problem, four types of solutions are introduced in detail, which are laying reference fiber, two-parameter matrix equation measurement, combination of two physical effects and special fiber discrimination. The principles, system, sensing performance and characteristics of each specific solution are analyzed, and these methods are discussed, compared and evaluated. Finally, it summarizes and looks forward to the research direction of solving cross-sensitivity issues.

A new kind of avalanche photodiode (APD) device applied in the visible light communication system was designed by using standard 0.18μm CMOS process. Compared to regular CMOS APD devices, the designed device adds a p-well layer to the deep n-well/p substrate structure, and an n+/p+ layer is deposited upon it. The n+/p+ layer acts as an avalanche breakdown layer of the device and an STI structure is used to prevent the edge breaks prematurely. The simulation results show that, the avalanche breakdown voltage is as low as 9.9V, the dark current is 1×10-12A, the 3dB bandwidth is 5.9GHz, and the responsibility is 1.2A/W. Due to the specific structure design of STI protection ring and short-circuit connection of deep n-well/p substrate, the dark current is reduced by about 2 orders of magnitude, and the bandwidth is improved by about 10% compared to that of regular CMOS APD.

ZnO columnar and cone-shaped micro-nano structures were grown on the surface of GaN-based LEDs by using the finite difference time domain method (FDTD). The Rsoft simulation software was used to analyze the influence of the geometric parameters of the two structures, such as the arrangement period P, height H, bottom diameter D, etc., on the light extraction efficiency of GaN-based LEDs. The results show that both structures can improve the light extraction efficiency of the device. The columnar structure performs the best when H=0.25μm, P=1.5μm and D=0.9μm, and its light extraction efficiency is 5.6 times that of flat panel LEDs without any structure. The cone-shaped structure performs the best when H=0.6μm, P=1.4μm, and D=1.4μm, and its light extraction efficiency is 5.3 times that of flat panel LEDs without any structure.

Pinning voltage (Vpin) is the key parameter affecting the charge transfer efficiency and full well capacity of the pinned photodiode (PPD) in CMOS image sensor (CIS). Experimental results show that Vpin increases with the total radiation dose (TID) effect, so it is of great significance to study the reasons in the design of anti-irradiation CIS. In this paper, TCAD simulation software is employed to analyze the electrical characteristics of the CIS and study the mechanism of Vpin affected by TID. The results show that when the concentration of trapped charges caused by irradiation reaches 3×1016cm-3, the depletion region near the shallow trench isolation (STI) isolates the pin layer of the PPD from ground, which causes the potential of the pin layer to be easily affected by the transfer transistor channel to increase. Thus under the same electron injection, the number of electrons stored in the PPD increases and the reset voltage needs to be higher, and Vpin increases with the increases of TID.

Aiming at the application of highly sensitive laser ranging in the 950~1100nm band, a high-performance single-photon photodetector module which is hybrid integrated with single-photon avalanche photodetector (SPAD), miniature thermoelectric cooler (TEC), active quenching and active recovery circuit (AQAR), temperature control unit, high-voltage unit and FPGA. The SPAD chip adopts the InGaAsP/InP material structure design that separates and absorbs the gradual charge multiplication. The internal electric field distribution is simulated by Matlab software, and the results show that the structure has good gain characteristics. The SPAD chip keeps working at low temperature through TEC refrigeration, reduces the dark count and improves the overall performance. The low-latency AQAR is composed of a high-speed comparator and a bandwidth amplifier. The quenching speed is about 1.2ns, which can effectively reduce the post-pulse effect. The test results show, the detection efficiency is 30.2% when the temperature is -30℃ and the dark count rate is 1.9kHz. The post pulse is 10.4% when setting the dead-time as 0.8μs. The designed detector characterized by high detection efficiency and low dark count rate, can be applied in miniaturized laser ranging.

In order to meet the needs of wideband fiber-optic time delay line with high-precision and large dynamic range, a time-stabilized 9bit wideband fiber-optic delay line is designed and demonstrated with magnetic optical switches and phase stable fiber. The experimental results show that, the sample can realize a transmission frequency of 1~18GHz in a wide temperature range of 60℃, the delay range is 0~2555ns with a delay step of 5ns, and the delay precision is less than ±5.8ps. Meanwhile, for a certain delay point, the dynamic range is 600ps and the precision is less than 1ps.

Based on coupled-mode theory, the eigen equations of core and cladding modes of the three-layer dielectric long-period fiber grating (LPFG) are presented by using strict mathematical model. Changes of effective indexes of the core and cladding modes in LPFG with refractive index of external environment are described, and the influence of the changes of the refractive index of external medium on resonant wavelength of LPFG is analyzed. The sensitivity of sensing measurement of LPFG can be significantly improved by coating with a specific film whose refractive index is sensitive to the change of the external environment, which provides a theoretical support to the optimum design of LPFG sensor and its practical application.

Time-to-digital converter (TDC) is a device for converting continuous time signal to digital signal, and it is the key component of TOF lidar. In this paper, designed is a two-stage coarse-fine combined time-to-digital converter circuit based on the traditional structure of counter coarse sampling and multi-phase interpolation fine sampling, and also a double echo receiving channel is added to receive multi-pulse echo signal. On this basis, a 17-channel multi-channel TDC system chip is designed. The system chip is designed with CMOS 0.11μm process, and the layout area is 0.6mm×3mm. The post simulation results show that the power consumption is less than 100mW, the average value of single input precision is 51.7ps, the dynamic range is 3.4μm, and chip presents good linearity under 1.2V power supply. Thus the TDC chip is suitable for signal timing of time-of-flight pulse lidar.

The high-quality preparation and optimization of semiconductor-based carbon nanotube films is of great significance for carbon nanotube-based electronic devices. The length of semiconducting carbon nanotubes is one of the important factors affecting the thin film. In this paper, high-purity semiconducting carbon nanotube solution was successfully prepared by poly［9-(1-octanoyl)-9H-carbazole-2,7-diyl］ (PCz). Through a cyclic deposition process, the short carbon nanotubes were effectively removed, and the average length of semiconductor carbon nanotubes was improved. On this basis, high-performance carbon nanotube thin film transistors were successfully prepared through standard process. The results show that the thin film transistor prepared by the optimized long carbon nanotube solution presents excellent electrical properties, with an on-off ratio of up to 107 and a mobility of up to 34cm2·V-1·s-1, which is 3 times higher than that of short tubes.

Vanadium oxide films were prepared on quartz glass substrates by reactive DC magnetron sputtering by adjusting the argon-oxygen flowing ratio in sputtering process, and the effect of sputtering atmosphere and post-treatment conditions on micro-structures and electrical properties of the films were investigated. Being annealed under 450 and 500℃ is beneficial to the formation of VO2, nevertheless, a large number of non-4-valent vanadium oxides appear in the films when the annealing temperature increases to 550℃. The crystallization of the films increases after they were annealed at 500℃, however, the cracks between the particles of films become more obvious, resulting in a significant increase in the resistivity of the films; meanwhile, the width of thermal hysteresis loop of the resistivity-temperature curve is narrower, and the phase transition temperature is higher during the heating process. A small amount of non-4-valent vanadium oxides were formed in the deposited VO2 films when the oxygen content in the argon-oxygen mixtures increases. The results show that the micro-structure, resistivity and phase transition temperature of VO2 films prepared by reactive magnetron sputtering are closely associated with the argon-oxygen ratio of sputtering atmosphere and post-annealing.

The influence of heat sink and ceramic substrate on the performance of semiconductor laser array with back-cooled packaging structure was analyzed. The equivalent resistance of the heat sink of composite diamond was reduced and the matching of thermal expansion coefficient was realized by rasterized thick copper filling technology. Using heat sink and ceramic substrate embedded welding technology, the heat dissipation ability and stability of the packaging structure was improved. Then the sample of 5Bar chip array with 0.4mm spacing was fabricated, and test results indicate that at 70℃, 200A and 1% duty cycle, the output power and the electro-optic conversion efficiency can reach 1065W and 59.2%, respectively. The sample shows good reliability in the 1824hours life test under high temperature and high current.

A model of double-layered microchannel heat sink with porous side fins is developed. Taking minimizing the maximum thermal resistance as the optimization objective and the aspect ratio of heat sink cell as the optimization variable, the constructal optimization was carried out for the heat sink with porous side fins under the constraints of given total volume of heat sink and volume proportion of fluid region. The effects of inlet velocity of coolant, porosity, the height ratio of upper channels to below channels, the volume proportion of fluid region and rib thickness ratio on the optimal constructs are analyzed, respectively. The results show that, with given the initial conditions, the maximum thermal resistance is 21.19% lower than its initial value after the aspect ratio is optimized. Decreasing the porosity is beneficial to reduce the maximum thermal resistance when the aspect ratio is smaller, while there is an optimal porosity to make the maximum thermal resistance minimize at a large aspect ratio. The changes of height ratio of upper channels to below channels and rib thickness ratio show few effects on the optimal construct.

Tungsten diselenide (WSe2) has ambipolar conductivity characteristics, which can be adjusted by external doping or changing source/drain metals. It is a special type of two dimensional nanomaterials and is expected to replace silicon (Si) in integrated circuits in the future. In this paper, the theory and experiments were combined to systematically analyze the influence of the source/drain contact characteristics of WSe2 field effect transistor on the conductivity type and carrier transport characteristics of the device. By preparing WSe2 field effect transistors with different metals as the source/drain contact electrodes, it is found that the actual Schottky contact barrier height of the metal/WSe2 contact greatly affects the on-state current of the transistor. The source/drain contact characteristics of the metal/WSe2 depend on the ideal Fermi level difference before contact, and also they will be affected by the interface characteristics, especially the Fermi level pinning effect.

High-quality GaN heteroepitaxy films were realized by using nitrogen plasma pretreatment of the sapphire substrate prior to the plasma-enhanced atomic layer deposition (PEALD) at 320℃. The crystal structures, surface morphology, elemental composition of the deposited GaN films were characterized by XRD, SEM, AFM and XPS. The results show that GaN films grown on the pretreated substrate exhibit improved crystalline quality with highly-preferred (002) growth direction. The as-grown GaN films are n-type with a carrier concentration up to 1.876×1019cm-3, resistivity of 2.551×10-2Ω·cm and the hole mobility of 13.04cm2·V-1·s-1. Most Ga elements form GaN with Ga-N bonds.

The spectral characteristics of three violet InGaN/GaN single quantum well samples with the same average In composition but different In composition distributions are studied in this paper. By analyzing the electroluminescence spectra, energy band structures, wave function overlap and carrier concentration distribution, it is found that the single quantum well sample with linearly increased In composition along the growth direction has the highest luminescence efficiency, while the sample with linearly decreased In composition has the lowest luminescence efficiency. It is considered that the linear increase of the In composition can weaken the influence of the polarization field on the valence band, making the valence band in InGaN well smoother, which not only reduces the height of the hole injection barrier, but also increases the hole concentration in InGaN well. The overlap integral of the electron-hole wave function in the well is also enhanced, and the probability of radiative recombination is improved, so the luminescence efficiency of the InGaN quantum well with the linear increase of In composition is significantly increased.

In order to study the difference of LED junction temperature under different driving modes, a difference electro-thermal dynamic model of pulse-driven LED was constructed from the perspective of power transfer according to the thermal structure model. And then, the junction temperature was calculated with injected powers which have same average power and different frequency. Lastly, the actual junction temperature was measured by forward voltage method for theoretical verification. The results show that the difference model can characterize the electro-thermal characteristics of pulse-driven LED, and the error between the predicted value and the measured value is about 4℃, which can basically meet the requirements of engineering applications. Furthermore, this model can be used to analyze the influence of LED heat capacity and thermal resistance on junction temperature under specific driving conditions, which provides a theoretical basis for LED design under different driving modes.

ITO films have become a research hotspot in the fields of nonlinear optics and micro-nano optics because of its ability to achieve epsilon-near-zero and easy modulation. In this paper, ITO films were prepared on silicon substrates with the RF magnetron sputtering method. Then the optical parameters are tested and fitted by ellipsometer, which explore the adjustment mechanism of the ENZ wavelength of ITO thin films by factors such as background vacuum, sputtering power, sputtering pressure, substrate temperature and film thickness. And by optimizing the process, the shortest ENZ wavelength of the ITO film is blue-shifted to 1094.4nm, breaking the limit of previous reports. This research extends the ENZ wavelength of ITO films to the near-infrared short-wave region, and will realize the application expansion of micro-nano optoelectronic devices in the short-wave direction.

Optical beamforming technology is a new type of broadband RF beamforming technology, which uses optical signal as the carrier to carry RF information, which means it uses optical signal to transmit and distribute RF signal to realize the control of RF signal. In this paper, the principle of optical beamforming based on microwave photonics is introduced, focusing on the optical incoherent beamforming architecture and optical coherent beamforming architecture. Through detailed theoretical formula derivation and software simulation, it is shown that the above two kinds of optical beamforming architectures can realize the signal synthesis for the received signals of multiple antennas. In view of the urgent demand of large array antenna units system for optical beamforming technology, proposed is an optical beamforming architecture suitable for the scale of thousand antennas by using the advantages of optical coherent and incoherent beamforming. It provides solution for the application of optical beamforming technology in phased array radar, electronic countermeasure and other fields.

In this paper, a fast quenching circuit is designed and simulated for free-running CMOS single photon avalanche diode (SPAD). In order to obtain more accurate simulation results, an enhanced SPAD simulation model is compiled using Verilog-A language, and I-V characteristic is expressed by three segmented functions. The fast quenching circuit is based on mixed passive-active quenching and capacitive sensing. A timing control circuit composed of the variable MOS capacitor is used to achieve hold-off time regulation. The simulation results show that the quenching time and reset time of the quenching circuit are 1.0 and 1.2ns, respectively. The hold-off time can be varied in the range of 1.02~3.55μs, which can meet the requirements of free-running CMOS SPAD detectors.

In order to eliminate the influence of power instability on the signal detection in laser speech transmission system, a method combining ensemble empirical mode decomposition (EEMD) and correlation coefficient is proposed to process the signal. The method decomposes the signal into several intrinsic mode functions through EEMD, and calculates the correlation coefficient between each component and the original signal. Then a determination threshold is set to distinguish the real signal and IMF component of trend term. It can overcome such shortcomings existing in traditional methods as the modal aliasing and need for subjective judgment of trend components. Simulation and experimental results show that the noise suppression effect of the improved EEMD is better than wavelet denoising. Furthermore, this method can effectively remove the trend caused by linear change of laser power and sinusoidal change of frequency less than 15Hz.

Based on the basic principles of compressed sensing (CS) and single pixel camera imaging, a new deep convolutional neural network architecture for image super-resolution reconstruction is redesigned. The new single pixel super-resolution imaging algorithm successfully combines deep learning image super-resolution reconstruction technology with compressed sensing single pixel imaging technology to develop an entirely new deep learning based optimized imaging method of single pixel camera. Compared with the conventional CS-based algorithms, the accuracy of image super-resolution reconstruction and the imaging quality of single pixel camera are improved effectively. The good performance of the new proposed deep learning imaging method of single pixel camera has been verified by simulation experiments of image reconstruction and imaging experiments of single pixel camera.

Lidar has become a necessary environment sensing device for unmanned intelligent vehicles. The existing vehicular lidar based on pulse signal is vulnerable to the mutual interference of other vehicular lidars, which leads to false alarm and misjudgment, and even traffic accidents. In this paper, the Boolean chaotic laser is used as the lidar detection signal. Combined with the scanning imaging technology, the chaotic laser imaging lidar system is constructed. The three-dimensional imaging of the target object is realized, and the ability of suppressing mutual interference is tested experimentally. The experimental results show that the three-dimensional reconstruction of the detected target can be realized under high-intensity interference. Based on the orthogonality of the Boolean chaotic waveform, the mutual interference can be effectively suppressed.

Space-based target measurement has the advantages of being all-day and free from atmospheric interference, but compared with ground-based human-guarded ranging, the space-based target moves fast and the priori information such as distance prediction is not enough, which makes the traditional ranging methods fail to extract the target distance trajectory effectively. To address this problem, in this paper, a laser ranging distance trajectory extraction algorithm based on Hough transform is proposed, which uses the linear correlation between target echo points to introduce the linear detection algorithm into the extraction of echo trajectories, and has the characteristics of adapting to the characteristics of space-based detection and strong anti-noise capability. The experimental results show that the root mean square error of the distance trajectory extracted by this method is better than 2.72m. The above method can accurately extract the distance trajectories of high-speed moving targets, providing a new way to extract the distance trajectories of subsequent spatial non-cooperative targets.

In order to improve the channel time-varying and the transmission reliability of satellite laser communications, a novel construction method of protograph quasi-cyclic low-density parity-check (QC-LDPC) codes based on the Zig-Zag (ZZ) structure is proposed. This construction method combines the protograph with the method of designing the shift coefficient of the Zig-Zag structure to construct the ZZ-QC-LDPC code with the check matrix of the girth-8 and the flexibly adjustable code-length code-rate. The simulation results show that under the same code-rate, the net coding gains of the ZZ-QC-LDPC code constructed by the proposed construction method, compared with the QC-LDPC code based on the arithmetic progression and protograph and the QC-LDPC code based on the greatest common divisor as well as the QC-LDPC code based on the large-girth fast encoding characteristics, can be improved by about 0.2, 0.1 and 0.64dB respectively at the bit error ratio of 10-6, furthermore, the ZZ-QC-LDPC code has the more excellent error-correcting performance within the wider code-rate range.

Aiming at the difficulty in extracting travel time caused by the uncertainty of the pulse width and signal-to-noise ratio of proton thermoacoustic signals in clinic, a travel time extraction algorithm based on dense network is proposed. The algorithm uses dense blocks instead of traditional convolutional blocks, combines features with different receptive fields, and introduces deep supervision and network pruning mechanisms. It uses labeled proton beam thermoacoustic signal data for learning to extract the required time information. The experimental results show that, compared with other algorithms, the proposed algorithm has higher accuracy and robustness for the extraction of proton thermoacoustic signal travel time, and shows the feasibility of real-time extraction.

To eliminate the influence of laser mode hopping on FMCW ranging, a mode hopping elimination method based on resampled signal phase splicing is proposed in this paper. It uses the result of the phase derivation of the resampled signal to locate the time when laser mode hopping occurs, and phase splices the peaks at both ends of the resampled signal to remove the signal in the mode hopping section. By performing Chirp-Z transformation on the resampled signal after phase splicing, the target distance spectrum not affected by laser mode hopping can be obtained. The system performs multiple measurements on the delay fiber of 21.16m. Experimental results show that this method can eliminate the influence of laser mode hopping on the distance measurement, and improve the measurement standard deviation to 12μm.