Short-wavelength mid-infrared (mid-IR) (2-2.5 μm wavelengths) photonics has tremendous applications in optical communication, ranging, satellite remote sensing, disease diagnosis, and military defense. As key components of short-wavelength mid-IR optical systems, integrated optoelectronic devices have attracted great attention in the past decades. With the merit of the wide transparency window of silicon material, silicon photonic integrated circuits exhibit great potential in developing short-wavelength mid-IR optoelectronic devices. In this review paper, we briefly discuss potential applications of short-wavelength mid-IR silicon photonics, and review its history and frontier progress from three aspects, namely, passive waveguide devices, nonlinear optics waveguide devices, and optoelectronic waveguide devices.

Aiming at the problem that it is difficult to detect infrared dim and small target accurately and quickly in complex background, a lightweight real-time network model YOLO-IDSTD for infrared dim and small target detection was proposed. Firstly, in order to improve the detection speed, the network structure of the feature extraction part was redesigned, and the Focus module was used to reduce the reasoning time after the input layer. Secondly, in order to enhance the detection ability, the path aggregation network was adopted in the feature fusion part and an improved receptive field block was added. Finally, four-scales detection was increased in the target detection part. Compared with the classical lightweight model YOLOv3-tiny on the infrared dim and small target data set, the recall is increased by 7.57%, the average pricision is increased by 1.92%, and the CPU reasoning speed is increased by 36.1%. The model can balance accuracy and speed, and the amount of calculation and parameters are significantly reduced. The size of the model is compressed to 7.27 MB, which reduces the dependence on the computing power of the hardware platform and realizes the accurate and fast detection of infrared dim and small targets.

Traditional multi-scale infrared and visible image fusion methods couldnot be well applied to all kinds of complex image environments, because the extracted image features were fixed. However, deep learning could independently select appropriate image features to solve the unicity in feature extraction of multi-scale methods. Therefore, an infrared and visible image fusion method based on the combination of convolutional neural network and non-subsampled shear wave transform (NSST) was proposed. Firstly, the binary classification map of the infrared target and background was extracted by convolutional neural network, and the classification map was accurately segmented by frequency-tuned (FT) saliency detection algorithm. At the same time, the NSST was used to decompose the source image in multiple scales and directions; Secondly, the target saliency combined with adaptive fuzzy logic algorithm was used for the fusion of low frequency sub-bands, and the high frequency coefficient local variance contrast method was used for the fusion of high frequency sub-bands; Finally, the fused image was obtained through the inverse transformation of NSST. The experiment results show that compared with the traditional image fusion algorithm, this method improves objective evaluation indicators such as information entropy, average gradient, spatial frequency, mutual information and cross entropy at least increased by 0.01%, 0.30%, 1.43%, 2.32%, 1.14%, respectively. The contrast of fusion image is greatly improved, and the background details are enriched, which is more conducive to human eye recognition. It can be widely used in electro-optical reconnaissance, electro-optical warning, multi-sensor information fusion and other electro-optical information fields.

Traditional methods of detecting and recognizing metal fatigue cracks by ultrasonic infrared thermal images mainly extract relevant thermal characteristics of infrared thermal images through image processing algorithms and match crack characteristics. This process is tedious and the recognition rate is low. Additionally, the effective characteristics need to be manually selected. Taking the advantages of active thermography and Convolutional Neural Network (CNN) in metal structure testing and automatic defect recognition, a vibrothermography crack detection and recognition method based on CNN was proposed. The specimens (metal platesin this work) were tested and thermal data sets were obtained by the proposed CNN-based vibrothermography. The designed convolutional neural network was applied to the feature extraction, recognition and classification of vibration-induced infrared thermal images with different crack sizes. In addition, the proposed method was compared with two common image classification network models and support vector machine. Experimental results show that the designed convolutional neural network can recognize and classify metal fatigue cracks with an accuracy of 100% on the experimental data sets, which is better than other network models and support vector machine, and can effectively detect and recognize metal fatigue cracks.

It was difficult to extract mineral features efficiently and quickly from large quantities of hyperspectral data obtained by airborne imaging hyperspectral spectrometers. An improved data-driven compressing method for mineral identification models was proposed in this paper, which pruned redundant neurons in neural networks to obtain efficient mineral identification models. Firstly, the average percentage of zeros driven by correctly identified samples in the validation set (C-APoZ) of each neuron was calculated as a criterion of importance for the neuron, so as to explore the contribution of the neuron to the network for identifying samples correctly. Then, the redundant neurons were pruned by setting the importance threshold, and the pruned network was retrained to improve the identification accuracy while preserving the correct identification abilities of the original network. Finally, an efficient compressed model for mineral identification was obtained through multiple iterative pruning. In this paper, the improved data-driven compressing method was conducted on the mineral identification models based on multilayer perceptron (MLP) to promote their efficiency. The hyperspectral data of the Nevada mining area collected by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) were applied to evaluate the proposed method. The results show that the proposed method obtained an efficient model for mineral identification with the compression rate of 3.33 and the identification accuracy of 94.35%.

Activation Functions (AF) play a very important role in learning and fitting complex function models of convolutional neural networks. In order to enable neural networks to complete various learning tasks better and faster, a new efficient activation function EReLU was designed in this paper. By introducing the natural logarithm function, EReLU effectively alleviated the problems of neuronal "necrosis" and gradient dispersion. Through the analysis of the activation function and its derivative function in the feedforward and feedback process of the mathematical model of the EReLU function exploration and design, the specific design of the EReLU function was determined through test, and finally the effect of improving the accuracy and accelerating training was achieved; Subsequently, EReLU was tested on different networks and data sets, and the results show that compared with ReLU and its improved function, the accuracy of EReLU is improved by 0.12%-6.61%, and the training efficiency is improved by 1.02%-6.52%, which strongly proved the superiority of EReLU function in accelerating training and improving accuracy.

Synthetic aperture radar (SAR) target recognition method based on decision fusion of convolutional neural network (CNN) and sparse representation-based classification (SRC) was proposed. CNN learned the multi-level features of SAR images through the deep networks, and then judged the target category to which it belonged. Studies had shown that CNN could achieve good recognition performance with sufficient training samples. However, for the conditions which were not included in the training samples, the classification performance of CNN usually decreased significantly. Therefore, the test samples to be identified by CNN were used for classification, and then the reliability of the current classification results was calculated according to the output decision value (i.e. the posterior probability corresponding to each training category). When the classification result was judged to be reliable, the decision of CNN was directly adopted and the target category of the test sample was output. On the contrary, several candidate categories were screened according to the decision values output by CNN, and then a global dictionary was constructed based on their training samples for SRC. For the classification results of SRC, the Bayesian fusion algorithm was further used to fuse it with the classification results of CNN. Finally, the target category of the test sample was determined based on the fused result. The proposed method integrated the advantages of CNN and SRC through a hierarchical way, which was conducive to taking advantage of them for different test conditions and improving the robustness of recognition. In the experiment, tests and analysis were carried out based on the MSTAR dataset, and the results verified the effectiveness of the proposed method.

In the process of vision-based autonomous UAV navigation, accurate identification of waypoints was the key to guiding the UAV to fly accurately toward the waypoint. However, when the UAV reached the waypoint recognition distance, the airborne image sensor was often affected by weather factors, defocusing, diffraction and other phenomena in the imaging process, which often resulted in blurred images and low spatial resolution. Thus, the accuracy of subsequent waypoint recognition was directly affected. Aiming at this problem, an aerial image super-resolution reconstruction algorithm with improved sparse representation regularization was proposed. Firstly, based on the sparse representation regularization framework, the regularization term of the objective function was constructed by using auto-regressive and non-local similarity constraints; Secondly, according to the characteristics of the image local variance that can effectively distinguish the edge area and the smooth area of the image, the regularization parameters were selected to obtain the objective function in the super-resolution reconstruction model; Finally, the Majorization-Minorization algorithm was used to solve the convex optimization problem of the objective function. Experimental results show that compared with the traditional regularized SR reconstruction algorithm, the proposed algorithm can effectively improve the spatial resolution of images, so that the reconstructed image contains more feature detail information, which provides help for waypoint recognition.

Restricted by the technology and material of infrared focal plane array (IRFPA), the infrared detector inevitably had some defective pixel such as blind pixel and flick pixel. The gray distribution and scale of blind flick pixel and infrared point target are consistent, which is easy to cause false alarm and missed detection of remote infrared detection system. Therefore, a dynamic real-time defect repair algorithm based on spatio-temporal statistical characteristics for infrared point target detection was proposed. Based on the indepth analysis of defect pixel, a spatial extreme value filter operator was constructed to extract the current frame feature mask, accumulate the historical mask value in the time domain, and make multi-dimensional judgment in combination with probability dynamic statistics. And the image pyramid was introduced to extract blind pixel, flick pixel and defect pixel clusters. Finally, the defect elements were eliminated by multi-scale median filter. The experiment takes DDR3 as off chip storage for FPGA hardware transplantation. The results show that the proposed algorithm cound be applied to all kinds of scenes requiring point target detection, dynamically update and repair new defective pixels, low computational complexity, strong real-time performance, the defect rate was reduced from 6 ‰ to 0.046 ‰, and the detection accuracy reached 98%.

Local delamination failure phenomena of indium antimonide infrared focal plane detectors (InSb IRFPAs) in their mass production have become a bottleneck restricting the improvement of their final yield. In order to determine the inducement of local delamination in InSb IRFPAs, the interface between the InSb chip and the underlying underfill with cohesion units was covered, and the specified parameters in cohesion model were optimized, finally the two-dimensional model of local delamination failure analysis of InSb IRFPAs was established. Simulation results are verified by the measured distribution characteristics of local delaminations, that is, (1) Most local delamination appears in the surrounding edges of InSb chip, and occupies a certain width; (2) Once the InSb chip is separated from the underlying underfill in the normal direction, the local delamination will expand gradually toward its both sides of the plane. In order to clarify the inducement of the local delamination, the evolution rule of the local delamination with different mixed-mode ratios is systematically analyzed under the jointed action of both the opening mode and sliding mode. The simulation results are highly consistent with the measured results when the mixed-mode ratio between the opening mode and the sliding mode is set to 4: 6. The local delamination of the InSb IRFPAs are ascribed to the jointed action of both the interfacial normal stress and the in-plane shear stress, is the typical mixed-mode local delamination mode, furthermore, the sliding local delamination mode is dominant.

Different from the traditional discrete spectrum temperature measurement, the essence of thermal imager temperature measurement is a kind of continuous spectrum temperature measurement based on the spectral response of detector in a certain band. In addition to the emissivity of the target will affect the relationship between the temperature measured by the thermal imager and the real temperature, the reflected environmental radiation is also an important factor affecting the temperature measurement results of the thermal imager. The current research on the temperature measurement accuracy of thermal imager, in the processing of the environmental radiation reflected by the target, mostly regard the incident environmental radiation as uniform or the target as a mirror reflector. Although this can greatly simplify the model, it is far from the actual situation. Based on the principle of radiometry and the spectral response characteristics of thermal imager detector, the temperature measurement model of the thermal imager for the diffuse target was established. The results show that the influence of environmental radiation on the temperature measurement of thermal imager is not only related to the reflectivity of the target and the temperature of the environmental radiation source, but also related to the projection solid angle of the environmental radiation source on the target. According to the model, the influencing factors of the temperature measurement of the thermal imager were analyzed. Then the influence of several typical environmental radiation conditions on the temperature measurement of the thermal imager was calculated and analyzed, and the experimental verification was carried out. On the one hand, the results can provide a reference for the design of temperature measurement of thermal imager, on the other hand, it can provide a theoretical basis for the error estimation between temperature measurement of thermal imager and real temperature under complex environmental conditions.

The trajectory prediction of infrared moving target is widely used in military and civilian fields such as monitoring and space-based remote sensing detection. When the relative velocity of the target is much higher, influenced by the fixed readout rate and integration time, the target trajectory points obtained by the traditional full field of view imaging information acquisition method are sparse, and it’s difficult to meet the accuracy requirements of target trajectory predication. To address this problem, an information acquisition method for fast moving targets based on dynamic windowing(DW) was proposed. The observation area was first imaged with full field of view, and after capturing the moving target, the target and its neighbors were imaged with a window to increase the frame rate. The discriminant matrix was obtained by analyzing the influence of the radiation characteristics of the detection scene on the working parameters of the system, and the dynamic adjustment of the window opening parameters was realized and the density of target trajectory points was enhanced. Finally, the window openning position was updated using the target trajectory prediction results to achieve the full-field coverage monitoring of a single target. The experimental results show that for the mid-wave infrared demonstration system, the method increases the target trajectory point density by 16 times and the system trajectory prediction accuracy by 2.6 times compared with the full field of view imaging information acquisition method. And the required data transmission bandwidth is reduced by 25%. This study can provide useful reference for the design of intelligent infrared sensing systems.

In order to evaluate the anti-jamming performance of the medium and long wave infrared dual-color detecting system, the dual-color target and interference simulation technology were studied. Based on multi-band infrared targets and interference generation technology, the multi-band target and jamming spectral radiation model and motion model were established. At the same time, based on the medium and long wave dual-color hardware-in-the-loop simulation system, through the medium and long wave infrared image simulator composed of MOS resistance array and DMD target simulator, multi-channel compound directional optical system and missile target attitude simulation system with the detection system under test, the medium and long dual-color image generated by the target simulator was compounded, collimated and processed by multi-channel compound directional optical system. After beam expansion, it is provided to the dual-color detection system to verify the simulation effect.

In order to study the composite interference performance of carbon fiber with different particle diameters on infrared/millimeter wave, the attenuation rate of infrared and millimeter wave was tested on carbon fiber with different particle diameters under static test conditions using test samples, and the ones with the best attenuation effects for the two were selected. The far-infrared and 8 mm wave were selected as the attenuation objects. The smoke screen test box was used to dynamically test and analyze the carbon fiber with the best particle size characteristics to the infrared/millimeter wave of composite interference performance. The experimental results show that carbon fiber powder has a better attenuation effect on infrared, and the interference performance of chopped carbon fiber on millimeter wave is more significant. 800 mesh, 1.5 mm and 4 mm are the best particle sizes for carbon fiber attenuation of infrared/millimeter wave. The composite interference performance of each band is the best when the ratio is 22%, 4%, and 74%.

Due to the influence of thermal stress and boundary conditions, the long linear long wave infrared(LWIR) detector will deform when it works, which may damage the chip or make the photosensitive surface un-confocal. The coplanarity evaluation of the detector under the condition of thermal-mechanical coupling is one of the important contents of the design of long linear LWIR FPA. The factors that may cause detector deformation were analyzed, and the main factors were identified by finite element model(FEM) simulation. Taking these main factors as variables, the coplanarity evaluation model of long linear LWIR detector which under the condition of thermal-mechanical coupling, was established based on the laminate theory. Error analysis of the coplanarity evaluation model was presented, and the error introduced by the model was acceptable in engineering. The coplanarity evaluation model was used to improve the structure of the focal plane assembly(FPA), and the effectiveness of the improvement was verified by FEM simulation and test. The verification results show that, after the structure is improved, the flatness change of photosensitive surface is reduced from 170 μm to 10 μm, which meets the design requirements of less than 20 μm.

In recent years, the greenhouse effect has become more and more obvious. The side effects brought by increasing of CO2 concentration have seriously affected people's production and life, and are even closely related to everyone's healthy. In defect of the large size, portability, high precision, and modularity of CO2 commercial sensors currently, a pyroelectric-based non-dispersive infrared (NDIR) method measuring CO2 concentration system was designed. The system design was mainly divided into four parts: air chamber structure design, signal circuit design, software control design and data processing. The air chamber structure design adopted a single-channel structure design, which was optically simulated. Finally, the size of the air chamber was determined, which effectively improved the measurement accuracy of the system. In terms of signal circuit design, a small signal amplifying circuit based on the differential method was designed to extract and amplify the effective signal from the noise to increase resolution. The software control design employed digital filtering algorithm to filter out interference and clutter, extract the effective value in the data, and improve the signal-to-noise ratio. In view of data processing, a gas test platform was built, and the temperature and humidity and peak-to-peak compensation formulas were used to compensate for the influence of temperature on the peak-to-peak value. Then, the gas concentration value was calculated using the curve fitting method at 25 ℃, and finally output through the serial port. After testing, the measurement range of the system is 5%, and the relative error is within 1500 ppm, which can meet the safety requirements of fire alarm, underground and other occasions monitoring.

The signal-noise ratio, dynamic range and sensitivity of long-wavelength (LW) infrared detector are limited by the charge capacity of digital readout integrated circuit (ROIC), which restricts the development and application of LW infrared imaging systems. The comparison and analysis of analog pixel and digital pixel ROIC technology were presented in this paper, the research status and main architectures of digital pixel focal plane array (FPA) were introduced. The 384×288 (25 µm) and 256×256 (30 µm) digital-pixel ROICs were designed with pulse frequency modulation scheme, and the designed comparator improved the power efficiency and robustness. Based on this, the digital LW FPA detector modules were designed with HgCdTe detector arrays, which measurement results were compared and analyzed with related works. The measured peak noise equivalent temperature difference are 3.4 mK and 1.9 mK, respectively, and the dynamic range achieves 96 dB. It’s confirmed that the digital pixel technology significantly improves the sensitivity and dynamic range of LW IRFPA, which manifests that this technology is a promising way to improve the performance of infrared detector.

The new generation of aerospace remote sensing instruments are developing towards high spatial resolution, high energy resolution, and high time resolution. Its core components are high-performance large-scale small-pixel short-wave infrared InGaAs focal plane detectors. The latest research progress in the design and fabrication of high-density InGaAs detector arrays was reported, and hybrided with matching Si-CMOS readout circuits to form a focal plane. The breakthroughs in dark current and noise suppression of high-density small-pixel detectors , megapixel focal plane flip chip interconnection and other key technologies were focused. The new flip chip interconnection technologies such as high flatness chip surface shape control, indium bumps convex morphology and high consistency control, and high-density flip chip interconnection control were solved. Developed 10 μm pitch 2560×2 048 focal plane detectors, which D* was better than 1.0×1013 cm·Hz1/2/W, the response non-uniformity was better than 3%, the effective pixel rate was better than 99.7%, and the dynamic range was better than 120 dB. This focal plane was used for laboratory demonstration imaging, and the picture was clear.

According to the application of underwater target detection, the corresponding 532 nm wavelength lidar system parameters were given. Combining the advantages of streak tube lidar and subcarrier modulated lidar, a prototype of underwater 3D imaging extended range lidar was designed. Compared with the common scheme of microwave modulated laser to generate high frequency pulse, the prototype adopted Q-switch technology to compress laser pulse, and then combined the characteristics of F-P cavity to generate high frequency laser pulse, which had the advantages of high peak power and high output energy. The experimental results show that the imaging distance of the prototype in clear water environment is better than 20 m, and it can capture the target details with a diameter of 9 mm at 13 m. In the turbid water environment, the range-extended capability of signal processing is 81.4%, and the range resolution error is 0.01 m. The experimental results provide a foundation for further improving the imaging range and resolution of underwater lidar and developing underwater imaging equipment.

Pseudo random code modulated laser ranging system could detect high frequency and low peak power by emitting high-order modulated laser, and achieve high signal-to-noise ratio by using high frequency detection and statistics. The system has the characteristics of small volume and light weight. It is a lidar system suitable for long distance. However, the measurement accuracy is related to the modulation frequency. In the past, high modulation frequency was usually used to achieve high-precision measurement. A laser radar prototype modulated by pseudo-random code was developed, which adopted 100 MHz modulation repetition rate, optical antenna with pupil diameter of 0.1 m. Through Gaussian statistics of the echo signal in the cycle, the high-precision ranging of 0.1 m was achieved in the laboratory environment when the signal-to-noise ratio was 5. Through theoretical and experimental analysis, it is proved that the measurement accuracy can be effectively improved by increasing the clock frequency and signal-to-noise ratio.

To improve the optical axis alignment accuracy of airborne laser communication system under the disturbance of body vibration and mechanical friction, a back-stepping sliding mode control method based on sliding mode observer was proposed. Firstly, the mathematical model of the airborne laser communication system was established, and then the disturbance value was estimated by the designed sliding mode observer. At the same time, the back-stepping sliding mode control law was gradually designed for the command conversion module, laser communication module and motor module, which realized the high-precision control for the optical axis of the airborne laser communication system. The experimental results show that the proposed method has better rapidity and accuracy than the fractional PID control method, the response time is only 0.4 s, the maximum space alignment error is only 0.3 m, the designed sliding mode observer can estimate the disturbance value quickly and accurately, the response time is only 0.3 s, and the maximum estimation error is only 0.1 m/s, 0.06 (°)/s2 and 0.07 A/s, which greatly improves the alignment accuracy of the optical axis in the airborne laser communication system.

The research status and progress of non-line-of-sight (NLOS) three dimensional imaging lidar were reviewed in this paper. Firstly, the background and basic concepts of NLOS imaging technology were introduced. The NLOS imaging technology based on laser pulse time-of-flight measurement, which was closest to lidar configuration, was selected as the focus of this paper. Then, the research progress of this technology was analyzed and summarized from two aspects of imaging system and imaging algorithm, respectively. It can be seen that scannerless NLOS imaging with SPAD array has become an inevitable trend in the future, and the non-confocal reconstruction algorithm adapting to SPAD array will also become the research focus. This new system of lidar will be widely used in military reconnaissance, security and anti-terrorism, unmanned driving, disaster rescue and other fields in the future.

Based on the external cavity constraint method, the experimental parameters of laser induced breakdown spectroscopy (LIBS) of Al and Si in bauxite were optimized. By setting the pressure, laser energy, delay time and other parameters, traditional LIBS and external cavity constrained LIBS (CC-LIBS) were used to ablate bauxite samples. The optimal experimental conditions were analyzed by selecting SiⅠ288.15 nm and AlⅠ308.21 nm as the characteristic spectrum. The results show that: when the pressure is 150 MPa, the deviation of the spectral line intensity is the smallest; when the energy is 80 mJ, the collected characteristic spectral line SNR is the largest; when the delay time is 1 μs, the SNR obtained by the two elements of Al and Si is the best, the optimal experiment condition is determined. Compared with traditional LIBS, the characteristic spectral line intensity and SNR collected by CC-LIBS have been improved, which provides new experimental basis and ideas for the detection of Al and Si elements in bauxite and has certain reference value.

In order to quickly and accurately obtain the three-dimensional surface profile of the inner wall of the deep hole structure and analyze the quality of the deep hole processing, a line scanning system based on laser harmonic modulation was proposed, and a reflective optical system that can penetrate deep into the deep hole structure was designed. The point cloud optimization algorithm for harmonic matching through time window filtering was studied. The algorithm used the harmonic modulation phase range to threshold the near-axis scanning area, thereby completing the point cloud data filtering. Experiments were conducted on three different types of deep holes, and the point cloud data was compared with the Handyscan three-dimensional imager. In this paper, the inner wall area of 5 cm×5 cm was quantitatively analyzed, and the three-dimensional point cloud images before and after optimization were compared. The point cloud before optimization obviously contained many stray points, and the comprehensive average deviation was 0.53 mm. After optimization, the noise was effectively suppressed, and the comprehensive average deviation was reduced to 0.12 mm. In the x-axis direction, the average value of the system position deviation was 0.240 mm, and in the y-axis direction, the average value of the system position deviation was 0.228 mm. Since the total amount of point cloud that needs to be calculated was reduced after optimization, the convergence speed had also been improved to a certain extent, and it stabilized above 3000 points, which was about 65.8% of the time before optimization. It can be seen that the system is suitable for the three-dimensional surface inspection of the inner wall of deep holes, and it provided a new idea for deep hole testing and data noise reduction.

To realize practical alignment-free distributed-cavity laser over a large dynamic range for adaptive laser wireless power transmission, experimental investigation was carried out based on an end-pumped Nd: GdVO4 laser of cat-eye retroreflector. On the basis of compensating the spherical aberration and field curvature(FC) of the receiver, optimizing the laser working distance and field of view(FOV) of receiver, it was found that the out-of-focus of cat-eye retroreflector induced by FC of each lens at the transmitter was main factors for limiting FOV angle(off-axis tolerance at receiving end). FC of the transmitter was analyzed and calculated based on the Zemax software, aspherical lens with corrected FC was designed and fabricated to avoid the out-of-focus of the transmitter when the receiving end was off-axis, the purpose of improving the transmitter FOV was realized. Using the optimized design aspherical lens, the laser output power was over 50% of its maximum value at a long working distance of 5 m within transmitter FOV of 4.6° in the experiment. The result was enhanced significantly compared with that using the common spherical lens, but there was still a certain gap between the ideal designed value and the experimental results. It is considered that the optical aberration of the thermal lens of laser crystal is a key factor for further optimizing the FOV at the transmitter.

The design and preparation of multi-band antireflection thin-film on barium fluoride optical elements is the key to improve the detection performance of photoelectric system. 1064 nm laser/long-wave infrared dual-band antireflection thin-film was designed and prepared on barium fluoride substrate. Based on the calculation method of the admittance in periodically symmetric structure thin-film system and the optimization algorithm of fitting periods and reference wavelength, study on the design method of the initial film system of the multi-band antireflection thin-film was carried out. The films were prepared using the thermal evaporation ion-assisted deposition method. The results show that the film has excellent optical properties with a transmittance of 94.0% at 1064 nm, average transmittance of 96.3% in the long-wave infrared spectral band from 8 to 12 μm, and transmittance of 99.4% at 8.2 μm. The laser/long-wave infrared dual-band antireflection thin-film can be applied to dual-mode composite photodetection optoelectronic equipment, which is of great significance to improve the working performance of the photodetection system.

In the laser communication and imaging system, whether the Cassegrain type optical antenna is used as a laser signal transceiver or an optical imaging device, the existence of aberrations will inevitably influence its signal intensity and imaging quality. By analyzing optical antenna of the third-order aberration theory and the perturbation theory, according to the relationship between the antenna gain factor and the occlusion ratio, a convenient and fast method for solving the Cassegrain type optical antenna structure was proposed. This method can not only consider the efficiency of the optical antenna, but also meet the requirements of the volume size and aberration of the optical system design. Especially in the case that only knowing the focal length of the optical system, the distance between the primary and secondary mirrors, the occlusion ratio, the structural parameters of the optical antenna can be calculated quickly. Not only gives the calculation formulas of the optical structure parameters for four types Cassegrain optical antennas, but also explains the advantages and disadvantages in the different application. According to comparing the calculation results of four typical optical antennas with the optimal results, the results show that this method is a convenient, fast and accurate method to solve the Cassegrain type optical antenna structure, and has practical significance in engineering.

Aiming at the real-time monitoring of position and velocity in smart flexible sliding sensor, a fiber optic sensing module for real-time monitoring of target displacement and velocity was designed. First, the temperature compensation module was used to solve the temperature cross-sensitivity problem; then, based on the analysis of the stress distribution simulation results of the sensing unit, the "meter" type FBG network structure was proposed; finally, the standard pressure gauge and the ball were used to complete the test of the position direction and the speed state, and a target state solution model suitable for this structure was proposed. The simulation results show that the average deformation of the target trajectory is about 0.32 μm, and the attenuation distance width is about 3.0 mm. The experiment carried out a sliding test on a 0.255 kg steel ball. The FBG stress sensitivity was better than 0.0206 nm/N. The FBG center wavelength offset can accurately determine the location of the object and the direction of the object's movement. The sensor module can monitor the movement state of the object in real time, and intelligently adjust the force and posture of the object. The results show that the plane positioning accuracy, motion angle and speed conversion of the sliding sensor system meet the design requirements, and according to the model function relationship, it can be known that the control of accurancy of the position, angle and speed can be achieved when adjusting the total amount of FBG in the sensor network. In summary, the system has the capability of real-time monitoring of the target position and movement status in the detection area, and is suitable for technical fields such as flexible intelligent assembly and intelligent bionic skin.

Infrared focal plane arrays (IR FPAs) play an important role in various infrared imaging systems. In order to improve the working temperature, quantum efficiency and sensitivity of IR FPAs, microlens arrays are usually used as light condenser for IR FPAs. Currently, materials of microlens array are usually different from the material of the infrared detector, so additional process means are required during integration of the two parts, which is difficult and inefficient. Based on metasurface, a planar solid immersion microlens array can be directly fabricated on the substrate material of the infrared detector, so that monolithic integration of the two can be realized. Aiming at the application of antimonide class type II superlattice infrared detector, a solid immersion infrared metalens based on GaSb substrate this was designed. The designed metalens worked in the mid-wave infrared band and could be applied to all incident polarizations. The designed focal length is 100 μm for all metalens devices designed here. Theoretically, the highest focusing efficiency at the target wavelength reaches 70.7%, and the numerical aperture (NA) reaches 1.15. This design can promote microlens array to be flat, ultra-thin and lightweight, simplifying the integration process of microlens array and infrared focal plane array. Besides, this design is expected to improve the detection efficiency of infrared focal plane device and reduce manufacturing cost.

Image space scanning optical system with tilt mirror usually only scanning imaging in one dimension, when tilt mirror is scanning imaging in two dimension, the effect of the tilt mirror’s coupling motion of azimuth and pitch can not be ignored. The basic forms of scanning optical system with tilt mirror were analyzed, and the influence of two-dimensional motion of the image space scanning optical system with tilt mirrors was analyzed. The incident optical axis direction and the spot size on the optical window at the different two-dimensional scanning angles were calculated. A method of image space two-dimensional scanning optical system with tilt mirror design and analysis were proposed. Building the image space two-dimensional scanning optical system model with Zemax, and the imaging performance, optical axis direction and window blocking at different angle of scanning were simulated and analyzed. Under different azimuth and pitch angles, the MTF of the optical system was greater than 0.4 at 17 lp/mm, and the max window blocking of the window was less than 21.4%.

The plenoptic camera can refocus after imaging, and obtain the position and direction information of the target at the same time with one exposure. Compared with the active distance measurement method and the traditional passive distance measurement method, the depth measurement method based on the plenoptic camera has the advantages of being difficult to detect and easy to calibrate. The plenoptic camera 3D imaging technology is a computational imaging technology that integrates the front-end optical system and the back-end information processing. The current research works mainly focus on the back-end information processing algorithm et al. There are few reports on the research of the front-end optical system. Therefore, the design of the front-end optical system was researched. Firstly, a calculation model was established for the depth resolution of a plenoptic camera based on multi-eye vision and the influence of optical system performance parameters was analyzed such as focal length and F-number on the object depth resolution. Secondly, the influence of factors was analyzed such as the blocking ratio of the two-mirror optical system and the magnification of the secondary mirror on the system parameters. Finally, a plenoptic camera main objective optical system for sub-kilometer-scale 3D imaging was designed comprehensively considering the design, processing, assembly, and ranging performance. The focal length of the system is 500 mm, the total length of the system is less than 163 mm, the telephoto ratio is less than 1/3, and the working temperature range is -40 -70 ℃. The full field of view MTF in 80 lp/mm is better than 0.3 at different temperatures. If the plenoptic camera uses this objective and a sub-pixel recognition accuracy algorithm of 1/8 pixel, a depth resolution of less than 5 m can be obtained at 0.5 km.

Single event latch-up (SEL) effect is one of the major factors that induce the failure of space-borne remote sensing instrument. To clarify the mechanism associated with the deterioration of polarization remote sensing camera induced by space high-energy particle radiation environments, the experiments were performed on the analog front-end signal processor of the directional polarization camera with heavy-ion and pulsed laser, for the purpose of identifying the single event effects sensitivity and providing technical guarantee for engineering design and test evaluation. The experimental results indicate that the analog front-end signal processor is susceptible to the SEL effect induced by heavy-ion, the linear energy transfer (LET) threshold is around 4.4-13.4 MeV·cm2·mg-1. Aiming at the low LET threshold, a design method of high power anti-latch up current limiting resistors in series to the analog and digital power supply terminal and the timing power on and off scheme was proposed. The results reveal that this method can effectively avoid the over-current burnout of the device and instrument failure caused by SEL. These research results provide significant reference data for the radiation-proofing design of analog front-end signal processor for the satellite-borne polarization camera and the experimental methods for single-event simulation on the ground.

Based on the photothermal conversion effect of doped fiber and the principle of Fiber Bragg Grating (FBG) temperature measurement, an all-fiber miniature soil moisture content sensor was developed. The 1480 nm pump laser was used to heat the cobalt-doped fiber embedded in the soil, and the temperature change was measured by the Bragg grating engraved on the cobalt-doped fiber. The in-situ measurement of soil moisture content was realized according to the linear relationship between temperature characteristic value and moisture content in the heating process. In order to verify the feasibility of this method and the accuracy of the sensor, a soil moisture content test platform was built and experiments were carried out. The experiments show that there is a linear relationship between the characteristic value of temperature and soil moisture content; the soil moisture content measured by the all fiber micro soil moisture content sensor is in good agreement with the drying method, and the maximum error is -1.41%, which is obviously better than the conductivity method. This new type of soil moisture content measurement method has the characteristics of miniaturization and low power consumption.

Aiming at the performance requirements of a DMD-based Offner spectral imager encoding in spectral dimension for a convex blazed grating, a macro-micro integrated optimization design method for convex blazed gratings was proposed. The three-dimensional polarization ray tracing algorithm was used to organically integrate the optical design of the Offner system in macro-level and the groove design of the convex blazed grating in micro-level. The composition and working principle of the coded aperture Offner spectral imaging system were introduced, and a MWIR convex blazed grating with an average diffraction efficiency of 85.47% was designed according to the requirements of the system. On this basis, a convex blazed grating with curvature radius of 120 mm, grating period of 99.945 μm, blazed angle of 1.1783°, groove depth of 1.834 μm was successfully fabricated by using an ultra-precision single-point diamond lathe. The test results show that in the spectral range of 3-5 μm, the maximum diffraction efficiency is 93.46% and the average diffraction efficiency is 84.29%, which is in good agreement with the theoretical design value. Thus, the proposed design method of the convex blazed grating is verified to be effective and valuable.

The optical information will experience the scattering phenomena, when it propagates in the scattering media, which will change the intensity and polarization information of the propagating light. And the depolarization property and the transmission property of the medium can be characterized indirectly, which can be used to classify and recognize the media. In theory, the Mueller Matrix (MM) can describe all polarization properties of the media, which plays a vital role in analyzing the depolarization properties of the medium, but its parameters are too complicated. However, the index of polarization purities (IPPs) obtained from the Mueller matrix can also describe the polarization properties of the media directly. IPPs are composed of ${P_1}$, ${P_2}$, ${P_3}$, which represent the weight differences of four non-depolarization pure systems decomposed from the depolarization system equivalently. The ${P_1}$, ${P_2}$, ${P_3}$ can form a three-dimensional space called purity space, in which different points represent corresponding depolarization systems. And they can be used for recognizing different depolarization systems. Compared to standard polarization indexes, the IPPs can express the more dimensional information of the scatter media, which has obtained many important research achievements in many aspects such as biomedical and target detection. We mainly introduce the IPPs theory, and meanwhile, review and discuss its great role in the analysis of depolarization of the different dispersion system, biological tissue imaging, medical monitoring and target recognition.

A new spaceborne imaging method based on squint isometric scanning was presented to overcome the problems of resolution degradation and atmospheric radiation difference with scanning angle in traditional cross-track scanning imaging method. Firstly, the principle of this imaging method was introduced, and the geometric imaging model was established according to the theory of geometric optics. Then, based on the geometric imaging model, the relationship between the scanning direction spatial resolution, vertical scanning direction spatial resolution and width with the scanning angle were given. Furthermore, the expressions of resolution and width for multi-angle observation via satellite pitch were derived. Finally, the simulation results of one pre-research spaceborne imager show that the resolution degradation is greatly reduced. When scanning angle is 60°, the edge view resolution is 2.5 times of central field of view far lower than traditional cross-track scanning imaging method 9.5 times. It provides a new solution for wide width imaging and has a certain reference significance for promoting the development of super wide width, high resolution and multi-angle spaceborne remote sensing.

In view of the influence of the scattering medium in the reconstruction of single-pixel imaging, the reconstructed image cannot achieve the best effect. The applicability of the correlation algorithm and compressed sensing algorithm for image reconstruction with or without the scattering medium was investigated. The influence of the spatial structure change of modulated information in the imaging path and the signal loss in detection path caused by the medium was analyzed, a near-infrared single-pixel imaging system was established, and the single-pixel imaging of penetrating the biological tissues scattering medium with the CGI algorithm and the TVAL3 algorithm was realized. It was found that the reconstruction time, peak signal-to-noise ratio and SSIM of the TVAL3 were better than CGI when there was no medium; while two of the three values of the CGI were better when there was medium, its maximum reconstruction time (0.304091 s) was smaller than the minimum (1.766299 s) of the TVAL3, and its minimum PSNR (9.9831dB) was higher than the maximum (9.170456 dB) of the TVAL3, and its SSIM (0.0982,0.1178) lay within the range of the SSIM of the TVAL3 (0.099258-0.497622). The results show that the CGI based on correlation imaging theory is more suitable for imaging scattering media, and the TVAL3 based on compressed perception theory is more suitable for imaging non-scattering media.

To achieve displacement measurement using the imaging grayscale of the image sensor, it is necessary to use the camera to image the target during the displacement process, and then establish the mapping relationship between the displacement value and the imaging grayscale value, i.e., the imaging grayscale model, and the measurement accuracy of this method depends on the imaging grayscale model and the grayscale noise level. In the actual measurement process, external error sources such as uneven illumination, target manufacturing errors, aberrations of the camera imaging system, and the variability of imaging characteristics between different internal image sensor units can cause the imaging grayscale model to deviate from the ideal situation, thus affecting the measurement results. To further improve the measurement accuracy, the modeling error caused by the aforementioned nonlinearities are taken into account, and a class of imaging grayscale models combining Fourier series and higher-order polynomials is proposed to improve the generalization approximation ability of the models and thus the modeling accuracy, correcting the grayscale distortion caused by the aforementioned error sources. On this basis, the displacement is solved by the sequential solution method based on the displacement continuity principle, and the experimental results show that the standard deviation of the displacement measurement error under the 10.46 mm stroke using this improved model is reduced from 56.4 μm before correction to 1.5 μm.

The fringe projection testing technology provides a non-contact three-dimensional profile measurement method with large dynamic range for various complex surfaces. In the dual-path point-diffraction interference projection testing system, the system structure parameters could significantly influence the surface testing accuracy. The system structural parameters were optimized based on the geometric model of testing system. In view of the projection angle calibration error in dual-fiber point-diffraction probe, the traditional method based on location of zero-order bright fringe could lead to obvious measurement error, due to the fact that the light intensity of the neighboring-order fringes was too close to distinguish from each other. To address this issue, an iterative correction method based on reference plane was proposed for the projection angel calibration, and it could effectively improve the testing accuracy. To demonstrate the feasibility of the proposed method, an experimental testing system was built to test the samples with various slopes dynamic ranges. The results show that the measurement deviation between the testing system after error correction and high-precision coordinate measuring machine is reduced from 0.418 2 mm to 0.021 1 mm, and the testing accuracy in the order of microns is achieved, providing a feasible way for the high-precision testing of various complex surfaces.

The system of photoelectric passive location with good concealment could improve the combat effectiveness of confrontation in complex electromagnetic environment. The system model of double-station passive location based on CCD was established. In order to improve the accuracy of calculation, the calculation method of target coordinate was provided according to the principle of least square method. The CCD reconnaissance model was established based on atmospheric extinction coefficient, the luminance coefficient of target and background, parameters of CCD imaging equipment. Based on the rule that the detection probability must be more than 10%, the operating distance of single CCD was calculated. Then, the change relations of the double-station location range and the distance of the stations was studied. By the target samples within the effective location range, the double-station location error was calculated. Then, the variation of mean value and standard deviation with the distance of the stations was analyzed. The calculation show that to certain weather and CCD, when the distance of the stations exceed a certain value, the location range would decrease rapidly. With the increase of distance, the location error and its dispersion first increase and then decrease. The analysis results have certain reference significance for optimizing CCD equipment parameters and reasonably configuring the position of observation stations observation stations. The analysis conclusion can be use for reference to optimize the CCD parameters and choose the reasonable location of observation station.

There are potential of polarization signal enhancement in smog environments at shortwave infrared wavelengths. The polarization characters for forward propagation at 532 nm and 1550 nm wavelengths were investigated by experiments. The smoke environment was made by burning smoke cake. It mainly composes of NH4Cl particles and water vapor. NH4Cl particles deposited stably when smoke cake burned in 7-16 min. The laser test platforms at 532 nm and 1550 nm wavelengths were developed to measure forward propagation character of horizontally linearly polarized light. Measurement errors of 532 nm and 1550 nm laser test platforms were nearly 1.03% and 0.89%, respectively. It mainly included fluctuation error of laser, time variation error, installation error and rotation error. The polarization state retention rate RoPS was tested when smoke cake burned in 7-16 min. The experimental results show that horizontally linearly polarized light has superior forward propagation performance at 1550 nm wavelength. And as the smoke concentration decreases, the difference of RoPS values gradually reduce. The work verifies the persistence of horizontally linearly polarized light at 1550 nm wavelength. It can provide experimental support for application of infrared polarization technology.

The non-interference phase retrieval method based on the transport of intensity equation was a method to obtain the phase by solving the intensity images. In the process of image acquisition, the selection of in-focus image was very important. But it was usually determined by subjective methods, which led to inaccurate in-focus positioning, thus affecting the accuracy of phase results. Firstly, an phase retrieval method based on the transport of intensity equation under adaptive focus was proposed; Secondly, the edge duty ratio was used to locate the acquired images in this algorithm. After solving the phase, the optimal focus position was located when the edge duty ratio locating position kept unchanging by the circular angular spectrum propagation; Finally, the phase of the sample was solved by using the transport of intensity equation. The result show that this algorithm not only improved the accuracy of phase retrieval, but also reduced the time to obtain a large number of images. In the simulation experiment, the correlation coefficient between the retrieval phase and the original phase reached 0.9866, and the RMSE error is 0.3050. In the actual experiment of microlens array, the error between the true height of the microlens and the height solves by the phase retrieval method proposed is only 5.7%, which proves that the algorithm can locate the optimal focus position in the field of microscopic imaging. And the algorithm is conducive to the development of auto-focus technology and improves the accuracy of phase retrieval.

As to pose measurement technology based on visual image, the global convergence of the nonlinear algorithm is uncertain, and the results depend on the selection of initial values, so the robustness of pose measurement cannot be guaranteed. Linear pose measurement algorithms have relatively high requirements for image processing. If the image coordinates of feature points are not accurately extracted, the pose measurement accuracy will be reduced. On the condition of natural light, the camera collects the image of positioning feature points, and the existence of high light regions in the image have some impacts on the extraction accuracy of feature points, which reduces the number of effective feature points and affects the pose measurement accuracy. To solve the problems above, a linear pose measurement method based on the optimal polarization angle was proposed. The camera was equipped with a polarizer. The optimal polarization angle solution model was established according to the Stokes vector. On the premise of the optimal polarization angle, the feature points images were collected and the image coordinates of the feature points were extracted. The linear solving model was established to solve the object pose. The experimental results show that this method can effectively reduce the high light regions in the image, which improve the imaging quality and improve the linear pose measurement accuracy. In the measurement range of -60° to +60°, the angle measurement error is less than ±0.16°. In the measurement range of 0 to 20 mm, the displacement measurement error is less than ±0.05 mm.

GaAs and Sapphire Crystal has been widely used in infrared region, optoelectronics field and military equipment, so the measurement of refractive index of two materials is of great significance to optical design, metrological inspection and industrial application. To improve the measurement accuracy of refractive index of two materials, microchip laser feedback interferometer technology was used to simultaneously measure refractive index and thickness. The system combined heterodyne modulation and quasi-common path to compensate for airflow and vibration, so it has the characteristics of high sensitivity, high precision and high stability, especially the simultaneous measurement and only the material needs to be processed into flake rather than prism shape. The experimental results demonstrate that the measurement accuracy of refractive index of GaAs and Sapphire Crystal (under ordinary light) has been enhanced to 10-3 and 10-4 respectively and thickness is 10-4 mm.

Magnetorheological polishing can efficiently remove low-frequency errors on the surface of optical elements, but it also introduces intermediate-frequency errors. The existence of intermediate-frequency errors has a serious impact on the performance of the optical system, which must be effectively controlled. The commonly used grating trajectories and spiral trajectories were studied. It was found that the regular polishing trajectory caused the convolution process to be inconsistent with the actual removal process, which would introduce symmetrical iterative errors. The iterative error is an important factor in the deterioration of the intermediate frequency error. Based on the research of grating trajectory and spiral trajectory, a trajectory optimization method for variable pitch spiral matrix trajectory was proposed to reduce the intermediate frequency error of optical components. The trajectory retained the advantages of simplicity and ease of the grating trajectory and the spiral trajectory by disrupting the pitch of the spiral matrix trajectory, and also changed the randomness between the trajectory lines. Through the power spectrum analysis of the surface shape before and after processing, it was verified that the trajectory can effectively reduce the intermediate frequency error of the surface, and the intermediate frequency convergence efficiency of the grating line and the spiral line is comprehensively improved by 26.59%.

Aiming at the problem that the existing accuracy evaluation methods can not effectively calculate the accuracy of star sensor under large dynamic conditions, a dynamic accuracy evaluation method was proposed based on the imaging model of star sensor and the invariance of star angle distance. The principle was clarified, and the calculation flow and statistical method were proposed. Based on the in-orbit data of FY satellite, the processing results of the proposed method and the traditional sliding window method were compared and the equivalence of the two methods under the same condition of small angular rate was analyzed, which verifying the feasibility of the proposed method. Based on the ground observation data, the measurement accuracy of two types of star sensors under different dynamic conditions was obtained. Compared with the existing dynamic accuracy evaluation methods, this method can effectively peel off the errors introduced by the test system, and more truly reflect the actual measurement accuracy of the star sensor under dynamic conditions.

Optical frequency comb is a kind of broad spectrum coherent light source, which is composed of a series of discrete spectral lines with equal frequency interval and has ultrahigh time-frequency accuracy. Since its birth, optical frequency comb has brought revolutionary changes to the development of precision spectroscopy, optical measurement, coherent optical communication, optical clock and other applications. In recent years, researchers have extended the frequency comb to the mid-infrared spectrum region (2-20 μm) by using novel laser gain media, nonlinear frequency conversion and micro-resonator techniques, and further expand the application range of optical frequency comb. In this paper, the generation mechanism, latest development and application of mid-infrared frequency comb are introduced.

Silicon-based photonics is expected to be extended to the mid-infrared (MIR) wavelength, due to the low absorption of silicon (Si) material in the range of 1.1 μm to 8.5 μm. With the needs emergence of communication window expansion, gas molecular detection, infrared imaging and other applications, the development of silicon-based devices in the mid-infrared wavelength is imperative. Silicon-based modulator plays an important role in the research and development of silicon-based optoelectronic devices in MIR. It is an indispensable link in long wave optical communication system, and can be used in on-chip sensing system to improve the signal-to-noise ratio and realize optical switching. It is found that silicon and germanium materials have greater free carrier effect and thermal-optical effect in the MIR band than that in the near-infrared band (NIR). It is proved that silicon-based materials have unique advantages in the development of mid-infrared modulators. The development trend and research status of MIR silicon-based modulators were summarized. The working principle and latest research progress of electro-optic modulators and thermal-optic modulators based on silicon and germanium materials were introduced. Finally, the mid-infrared silicon-based modulators were summarized and prospected.

The mid-infrared band contains two atmospheric windows as well as the molecular fingerprint region, and therefore has important applications in infrared imaging and detection. Conventional mid-infrared optics are expensive and need complicated fabrications limited by the material and processing technology in imaging. In terms of the detection, limited by the small molecular absorption cross-section, the sensitivity is extremely low and there is a great challenge for the trace chemical detection. Metasurfaces are two-dimensional arrays composed of artificial building blocks at the subwavelength scale. They have the characteristics of small size, easy integration and high degree of freedom, which may provide a new implementation scheme for manufacturing the low-cost, light-weight and integrated mid-infrared optical devices. Surface-enhanced infrared absorption can effectively enhance molecular vibration signals and improve the detection sensitivity. In this review, the mechanism of mid-infrared metasurfaces in electromagnetic wave regulation and the principals of mid-infrared detection applications are introduced. The research progress in the imaging and detection of mid-infrared metasurfaces is sorted out, including the polarization imaging, tunable and reconfigurable metasurfaces, other special functions and metasurface structures using gold, silver, aluminum, graphene, silicon, germanium and other materials based on plasmon or bound states in the continuum principles for the detection.

Driven by the development in big data services, the conventional optical fiber communication window was shifting from C-band to C+L band to meet the continuously increasing demand for bandwidths. Exploiting new wavebands became a crucial problem within the optical communications community. The 2 μm spectral range between near-infrared and mid-infrared held advantages of low transmission loss and broad gain bandwidth, which made it a promising candidate for the next window of free space laser and optical fiber communications. Even though the commercialization of the 2 μm optoelectronic devices was at early stage, recorded single-lane 100 Gbit/s transmission had been achieved in the laboratory. In the meantime, developing functional elements in this wavelength range was attracting extensive interests. In this paper, the recent advances of 2 μm silicon photonic device were introduced. Photonic integrated components on other platforms like III-V, thin-film lithium niobate, silicon nitride, and chalcogenide glass were also discussed. Finally, the 2 μm was envisioned on-chip photonic integrated devices.

The 2 μm wavelength band, which is the closest to the O and C communication band in the mid-infrared band, has gradually attracted widespread attention. A Mach-Zehnder modulator in the wavelength of 2 μm was optimally designed and simulated. According to the distribution characteristics of the optical mode field in the wavelength of 2 μm, an SOI substrate with the top silicon thickness of 340 nm was selected. Combined with the process of the etching depth of 240 nm, the optimal rib waveguide width was 600 nm and the thickness of the slab layer was 100 nm. By optimizing the doping concentration and the positions of the doping regions, an optimal overall performance of the modulator was obtained. The modulator operated with the static extinction ratio of 23.8 dB, the optical loss of 5.34 dB/cm, the modulation efficiency of 2.86 V·cm and the 3 dB EO bandwidth of 27.1 GHz at the reverse bias of 4 V. Besides, compared with the device with the top silicon thickness of 220 nm, the overall performance of the modulator was more superior. The research content provides a basis of the device tape-out, and also provides a new idea for the design of the modulator required for the 2 μm band optical transceiver integrated module.

In recent years, mid-infrared (wavelength range of 2–20 μm) integrated photonics has received a lot of attention for its potential applications, including absorption spectroscopy, thermal imaging, and free-space communication. The mid-infrared, which includes several atmospheric transparency windows, has an inherent advantage for sensing applications. The mid-infrared photonic devices also benefit from the mature technologies developed in the near-infrared for device design, test, and fabrication. In addition, integrated photonic sensors have demonstrated comparable sensitivity to their bulk counterparts, while featuring low power consumption, low cost, compact structure, and easy integration with other devices. Therefore, the mid-infrared integrated photonic sensors will play an important role in industrial detection, scientific research, medical diagnosis, military security, life, and other fields in the future. Here, Recent advances in the mid-infrared integrated photonic sensors have been reviewed. Three major components, sensing unit, spectrometer, and detector were discussed. An outlook for its future development was also proposed.

In recent year, mid-wave infrared detection technology has rapid development, and plays an important role in variable applications. Among different kinds of mid-infrared detectors, Ga-free InAs/InAsSb type II superlattice (T2 SL) detectors have the potential to achieve higher minority carrier lifetime and higher performance due to the removal of Ga-related defects. The application of photonic crystals is another way to improve the performance of detectors by optical control, such as the improvement of responsibility and the decrease of the dark current. With higher responsibility and lower dark current, the detector can have higher operating temperature, which results in low Size, Weight and Power (SWaP). At the same time, the photonic crystals can also realize the optimization of optical performance such as broadband spectrum responsibility without changing the material structure. The material growth and device design of InAs/InAsSb T2 SL detectors and photonic crystal structure detectors were reviewed and discussed in this paper. Two methods to improve the performance and the progress of mid-wave infrared detectors were introduced in detail.

In recent years, chalcogenide glasses have attracted much attention in the field of integrated photonic devices because of their ultra-wide infrared transmission spectrum, high linear refractive index, extremely high optical nonlinearity, and ultrafast nonlinear response. Firstly, the fabrication of chalcogenide glass integrated optical waveguides was reviewed, the progress of chalcogenide integrated photonic devices in infrared sensing and high-performance nonlinear applications was summarized. Then, the chalcogenide phase-change photonic devices in optical switching, optical storage, and optical computing were introduced. Finally, the current problems in chalcogenide glass photonic devices were summarized, and the future research directions were prospected.

Mid-infrared photonic integrated circuits have been attracting a lot of interest for applications in environmental monitoring, medical diagnosis and national defense. However, the integration of laser sources with low-loss mid-infrared waveguide circuits is challenging. Quantum cascade lasers (QCLs) are important semiconductor laser sources operating in the mid-infrared spectral range. In this review paper, the research progress of the photonics integration of mid-infrared QCLs in recent years was introduced. Several different approaches were reviewed, including monolithic integration on InP, monolithic integration on silicon, heterogeneous integration on silicon and III-V/Germanium hybrid external cavity laser.