Complying with the trend of small size, multi-functionality, and high density integration of photoelectric detectors and arrays, a high-performance solar-blind and X-ray dual function detector basedon ultra-thin Ga2O3 was reported. Based on the metal-organic chemical vapor deposition, through fine tuning of growth at high temperature, a thin thickness (70 nm) of high-quality gallium oxide heteroepitaxial thin film is realized. Owing to the ultra-wide band gap of Ga2O3 and the high quality of the film, metal-semiconductor-metal structure photodetector based on this film has achieved a photo-to-dark current ratio of 5.5×107, detectivity of 4.65×1015 Jones, external quantum efficiency of 3.53×104%, and responsivity of 72.23 A/W in solar-blind ultraviolet detection band. What's more, the above-mentioned solar-blind ultraviolet performances remain stable relatively at different solar-blind light intensities (14.7~548 μW/cm2). While for X-ray detection, an ultra-high sensitivity of 1.91×104 μC·cm-2·Gy-1 is achieved, which exceeds the previously reported Ga2O3 thin-film detectors under the equivalent thickness. Besides, the device can still achieve comprehensively high performance at a lower operating voltage. The improvement of film quality, ionization of intrinsic oxygen vacancies, and photoinduced Schottky barrier reduction effect etc. conribute to the excellent photoresponse performance of this Ga2O3 thin-film detectors under both solar-blind and X-ray illumination. Additionally, the cascade effect casused by the X-ray induced high-erergy electrons is another critial aspect for the high X-ray sensitivity of the device. This work provides potential inspirations for ultra-thin solar-blind and X-ray detectors with high performance and low power consumption in the future.

The bandgap of silicon-based germanium tin and germanium lead alloys can be adjusted with the composition, and can be transformed into a direct bandgap semiconductor material. It is an ideal material for developing silicon-based infrared luminescence and detector. This work first introduces the growth of germanium tin and germanium lead alloys, and then reviews the research progress of germanium tin optoelectronic devices. The germanium tin photodetector has developed towards high responsivity and long cut-off wavelength with increasing tin content. The research of germanium tin lasers is focused on low lasing threshold, high lasing temperature and electric pumping. In addition, this work also briefly introduces the research on germanium lead material and optoelectronic devices. With the development of silicon-based high-efficiency light sources and detectors, group IV alloys will continue to show important application value in the field of silicon-based infrared optoelectronic integration.

The GeSn photodetectors (PDs) have drawbacks such as the slow response speed and the poor signal-to-noise ratio. To overcome these disadvantages, we report one polarization-sensitive dual-mechanism-enhanced GeSn PD that contains both Fabry-Pérot (F-P) mode and Surface Plasmon Polaritons (SPP) mode. The F-P mode originates from the GeSn film assisted by an embedded SiO2 film, while the SPP mode is associated to the added Au grating on the GeSn film. Simulation results show that these two types of modes can increase the optical absorption of GeSn from 20% to 80% at 2 000 nm. Moreover, under TM/TE polarization, absorption of the sample are 80% and 2.6%, respectively, and the extinction ratio is 31. Such a high extinction ratio indicates that the GeSn PD has great polarization selectivity. These results provide new ideas for the development of innovative GeSn PDs.

The quantum cascade detector is a photovoltaic inter-subband transition infrared detector. Through the cascading subband in the chirped quantum well with gradient thickness, a built-in electric field is generated to transport the photo-generated carriers in the active region. No bias voltage is applied when the device is working, thus avoiding the generation of dark current noise, and achieving room temperature long-wave infrared response. Due to the low absorption coefficient of the inter-subband transition and polarization selection rule, quantum cascade detectors currently have several problems such as low responsivity, no response to normal incidence, and temperature sensitivity of the detectivity. To address these issues, three quantum cascade detectors with new active regions are introduced, including quantum dot/well hybrid, bound-to-miniband diagonal transition, and mini-step transport active regions, exhibiting improved performance for mid, long, and very long wavelength infrared detection.

The Signal-to-Noise Ratio(SNR)of coherent detection system, which is affected by the non-linear effect of the photodetector, can not achieve the SNR level under the shot noise limited operation. Hence, there is an optimal local optical power to maximize the SNR. Aiming at the problem that the optimal local optical power of the system is difficult to determine, the theory of optimal local optical power based on balance detector is analyzed firstly. A method for determining the optimal local optical power which measure the heterodyne signal directly and calculate the SNR based on cross-correlation method and spectrum method is proposed subsequently. The experiments are conducted by setting up the experimental system for testing three type photodetector. The results demonstrate that the curve of measured SNR versus the local oscillator optical power basically consistent with the theoretical value, the optimal local optical power can be accurately measured for different detectors. The proposed method in this paper can be used to determine the optimal local optical power of a coherent detection system and improve the system SNR.

Infrared detection technology has important applications in laser ranging, imaging, remote sensing, night vision and other fields. It is the focus of research to reduce the size, weight, power consumption and cost of infrared photodetectors, and to improve the performance of the detectors. This article summarizes the development history, working principle and researche status of infrared detector technology, and prospects its future direction. The content mainly covers photonic infrared photodetectors and their arrays based on mercury cadmium telluride, type II superlattices, quantum wells, quantum dots, silicon-based germanium tin and other materials. The cost reduction of infrared systems ultimately depends on the consumption under normal temperature conditions. Whether the pixel density of the current limit detector array matches the background limit and diffraction limit performance of the optical elements of the system, materials such as HgCdTe, type II superlattices and colloidal quantum dots are selected to improve the room temperature performance of the photon detector. Various infrared detectors have their own characteristics in terms of performance and complement each other in practical applications.

In this paper, two improved network models, SVM (Linear)-based VGG19 and XGBoost-based VGG19, are constructed by combining the VGG19 convolutional neural network with two machine learning algorithms. Moreover, the VGG19 model and the two improved models are employed to classify bacterial pneumonia and viral pneumonia images. Additionally, the performances of the three models are evaluated and compared, the results show that the average accuracies of the three models are all above 85.9%. The improved VGG19 models show superior stability in accuracy over conventional VGG19 model, and the comprehensive performance of XGBoost-based VGG19 model is best, which verifies the effectiveness of deep learning models combined with machine learning models.

In the process of bridge crack detection based on intelligent image processing, the number of images collected is huge, and the detection is very time-consuming. So, a fast screening method for bridge crack images is proposed. First, the edges in the image are extracted and the longest edge is found. Secondly, the minimum circumscribed circle related to the longest edge is obtained and then the circle radius is used to filter and classify the image by comparing with a threshold. The threshold is automatically determined by building an adaptive calculation model based on image resolution. Experiments show that the proposed method can quickly and accurately screen the crack images from the non-crack images, which greatly improves performance of the crack detection system.

Due to the geometric distortion of fisheye images, the existing person detection algorithms based on fisheye images have the problems of low detection accuracy and high computational complexity in post-processing.A rotation-aware person detection algorithm was proposed to solve the problems. First, the algorithm adopted an anchor-free network structure and used heatmap to predict the center point of the bounding box, there was no need to apply non-maximum suppression on the bounding boxes during post-processing which avoids the calculation of intersection over union(IoU) between rotated bounding boxes. Then,a Gaussian kernel function with angle and scale adaptation was adopted to fit the center distribution of person with distortions,which greatly reduced the interference of background features,and balanced the difference of person with different sizes under fisheye images during the bounding boxes regression. Finally, the Angle-IoU(AIoU) was designed to combine both IoU loss and Ln-norm loss, indicator function was used to deal with inconsistent regression between IoU loss and Ln-norm of angle regular term. The proposed algorithm was verified on public datasets, experimental results show that the algorithm has achieved the state-of-art performance with an average mAP of 51.33%, detection frame rate reaches 49 fps, which is 139% higher than the detection algorithm with anchor-based network structure, the comprehensive performance of the algorithm is better than other existing person detection algorithms in overhead fisheye images.

In order to solve the problems of short detection distance, difficulty in acquiring large field of view and high-resolution real-time imaging, and poor quality of reconstructed images, which are caused by the limited information acquisition methods and insufficient interpretation capabilities of traditional imaging technology with object-image conjugation as the core, computational imaging technology with core information-driven came into being, and it has shown great potential in photoelectric detection. In this paper, the concept and connotation of computational imaging are illustrated from the beginning of the bottleneck problem in traditional imaging. And then the computational media, computational optical systems and computing processing in the imaging link are deeply analyzed. Meanwhile, the role, advantages and disadvantages of computational imaging in imaging and detection are summarized, and the future development in photoelectric detection field is prospected.

To improve the scene perception ability of traditional imaging lidar system and the generalization ability of the signal processing algorithm, a cognitive method of imaging laser radar based on deep learning is proposed. Through the result of deep learning point cloud target detection algorithm, the core imaging parameters are further regulated, and the cognitive feedback is formed, improving the system imaging quality and environmental perception. To test and verify the feasibility of the proposed method, a cognitive imaging laser radar presentation module is designed and implemented. Through the experimental comparison and analysis, three imaging parameters of laser emission power, scanning field of view and scanning angular resolution of imaging system are selected for cognitive feedback, and the module combined with the deep learning method realize the dynamic interaction learning of the scene, which has solved the problem of solidification of traditional lidar imaging parameters. The experimental results show that the cognitive imaging mode based on deep learning can effectively improve the generalization ability and target detection accuracy of the existing deep learning point cloud target detection algorithm.

A coherent anti-Stokes Raman scattering microscope is built by using a supercontinuum fiber laser, towards a solution of the disadvantages in current imaging system, such as the cost and bulk-size. Firstly, the theory of supercontinuum fiber laser-based coherent anti-Stokes Raman scattering imaging is deduced and its influencing factors are analyzed. An experimental setup for the supercontinuum fiber laser-based coherent anti-Stokes Raman scattering microscope is then built up, while its experimental feasibility is demonstrated. Different influencing factors, including objective lens, laser power and concentration, are selected to demonstrate that the test results are highly consistent with theoretical ones. The results prove the theoretical and experimental feasibility of coherent anti-Stokes Raman scattering microscopy based on supercontinuum fiber laser.

The generation of 343 nm femtosecond laser with high beam quality by the third harmonic generation of an all solid state femtosecond laser was reported. The fundamental harmonic is a commercial Yb:KGW mode-locked laser with a pulse duration of 105 fs, a repetition rate of 76 MHz and a central wavelength of 1 030 nm. Firstly, the second harmonic radiation is achieved with 60% optical-to-optical (1 030 to 515 nm) conversion efficiency. Then, the third harmonic generation based on type Ⅱ and typeⅠ phase-matching BBO crystals are studied respectively. With the type Ⅱ phase-matching BBO, the maximum output power of 0.71 W is achieved under the fundamental power of 5 W, which corresponding to the optical-to-optical conversion efficiency of ~14%. The ultraviolet output power of 1.01 W is obtained corresponding to an optical-to-optical (1 030 to 343 nm) conversion efficiency of 20.2% with type Ⅰ phase-matching BBO. The beam quality of the high power ultraviolet laser at 343 nm is better than 1.3.

Based on the saturable absorption properties of narrow band gap semiconductor PbSe, saturable absorber devices are achieved by physical vapor deposition using pure PbSe powder as the precursor and transferred by optical fiber probe. And pulse fiber lasers with different wavelengths are built. By using a simple ring cavity in near infrared, the stable mode-locked output is realized with almost unchanged devices in the range of near-infrared 1~2 μm, and the central wavelengths are 1 060.46 nm, 1 563.24 nm and 1 908.34 nm respectively, the fundamental frequencies are 0.593 MHz, 13.59 MHz and 10.25 MHz separately, and the pulse widths are 30.53 ns, 4.26 ns and 1 ns respectively. This result expands the applications of the new nanocrystalline material lead selenide compound, provides a solution for the wavelength regulation of pulsed fiber laser, and satisfies the application requirements of multi-wavelength tunable laser in biomedical, monitoring and other places.

A stable Q-switched and mode-locked Ytterbium Doped Fiber Laser (YDFL) based on layered semiconductor β-InSe as Saturable Absorber (SA) were demonstrated for the first time. The modulation depth and non-saturable absorbance of the SA were 47% and 20%, respectively. After inserting the SA into YDFL, the stable Q-switched pulse operation can be easily obtained with the repetition rate range from 53.42 kHz to 217 kHz. The minimum pulse duration was 630 ns and the maximum single pulse energy was 47.9 nJ. By optimizing the laser resonator, a stable mode-locking pulse with repetition rate of 10.82 MHz, maximum output power of 51.2 mW and maximum single pulse energy of 4.7 nJ can be achieved. The experimental results demonstrated that β-InSe SA has great potential in near infrared ultrafast nonlinear optical.

Based on an organic nonlinear optical material, Maleic Acid-Doped Polyaniline (MADP) Saturable Absorber (SA), a stable Q-switched pulse operation was realized in an erbium-doped all-fiber laser for the first time. In this experiment, the modulation depth and saturable absorption intensity of the MADP-SA were measured at 13.9% and 0.336 MW/cm2 using the twin detector technique, respectively. The MADP-SA is inserted into the fiber resonator in the form of a thin film sandwich. The stable Q-switched pulse operation are achieved with the repetition rate range from 33.78 kHz to 87.01 kHz, the narrowest pulse width of 2.29 μs and the maximum single pulse energy of 54.64 nJ. MADP can be considered as a good candidate for pulsed fiber laser applications and other optoelectronic devices.

Field-effect transistors are the key component of modern electronic technology, which can control the on/off states of circuit by varying voltages. With the emergence of more new semiconductor materials, the selection of channel materials for field-effect transistors is much more diversified. In recent years, perovskite materials, as a new type of organic-inorganic hybrid semiconductor material, has developed rapidly in the fields of photovoltaic devices and light-emitting diodes, but their development in field-effect transistors have been restricted due to the serious intrinsic ion migration. Ion migration in perovskite materials can lead to partial shielding of grid electric field, which greatly affects the modulation of grid and reduces the field-effect mobility. Here, we systematic elaborate the mechanism of ion migration, and then summarize several methods that can inhibit the ion migration. Finally, the development of perovskite transistors is also prospected.

Cancer is currently a common problem facing human beings. Early diagnosis is a key factor in reducing cancer mortality. Due to its sensitivity to the microenvironment, fluorescence lifetime imaging microscopy (FLIM) can not only distinguish early cancer tissues from normal tissues, but also monitor the drug treatment of cancer. Therefore, FLIM has great application potential in cancer diagnosis. This article introduces the basic principles and detection methods of FLIM, summarizes the endogenous and exogenous fluorescence characteristics and their relationship with cancer. In addition, this article mainly reviews the recent applications of FLIM in the diagnosis of cancers in the nervous system, respiratory system, digestive system, reproductive system, urinary system, endocrine system and skin system, and discusses the application advantages, limitations and future development trends of FLIM in cancer diagnosis.

Raman Spectroscopy (RS), which is based on the inelastic scattering of photons, could be utilized as an analytical tool with the advantages of fast, real-time, and non-intrusive. Nowadays, RS is widely used in various research fields. This spectroscopic technique can provide the chemical composition information of cells and tissues, and detect the differences in the diseased cells and tissues. Thus, RS has a great application prospect in the field of medical laboratory science. This article summarizes variety RS techniques that might be used in the medical laboratory. Key problems in the application of RS on biological fluid samples are summed up. For biological fluid samples, the applicability of RS on blood samples, urine samples and cerebrospinal fluid samples are evaluated. The collection and preservation methods of samples for RS analysis are also summarized. Meanwhile, generalizes the processing and analysis methods of RS data. Through spectral preprocessing, statistical methods and machine learning, the relative features could be extracted and the classification recognition could be carried out. In that case, the mapping of RS could be realized and biochemical information could be collected. At last, the difficulties of RS in the application of medical laboratory and diagnosis are discussed. The problems and development prospects in clinical transformation are highlighted.

Brain science and brain-like research have become the strategic frontier of international competition. The rapid development of artifical intelligence and deep learning has put forward an urgent demand for the computing capacities. In the traditional von Neumann architecture, the physical separation between memory and computing units results in power consumption wall and memory wall problems. Besides, Moore's law is gradually slowing down. Photonic neuromorphic computing, which fully combines the characteristics of high-speed optical communication, optical interconnection, optical integration, silicon-based optoelectronics and neuromorphic computing, has the advantages of ultra-high speed, large bandwidth and multi-dimension. It has wide application prospects in the fields of high-performance computing and artificial intelligence. Furthermore, it is a highly competitive solution that breaks through the limits of traditional microelectronics computing in the post-Moore era. This article reviews the work of the main research teams at home and abroad on the theory, algorithms, and devices of photonic neurons, synapses, and neural networks, and puts forward a prospect.

Combined with the time delay reservoir computing and vertical cavity surface emitting laser, based on the existing fiber optic platform, an experimental study on the time delay reservoir computing system with the 1 550 nm waveband vertical cavity surface emitting laser as the nonlinear node is carried out. The results show that a Santa-Fe chaotic time series prediction task and a single nonlinear channel equalization task can be successfully implemented in the experimental system. Based on the vertical cavity surface emitting laser that can achieve two polarization modes coexistence under certain parameter conditions, external signals are further injected into the two polarization modes of vertical cavity surface emitting laser simultaneously, and the parallel processing of Santa Fe chaotic time series prediction and signal nonlinear trace equalization is successfully completed, however, the performance of parallel tasks processing is weaker than the performance of single task processing. Besides, the performance of the parallel task processing is improved with the increase of the external light injection intensity, and the performance of the side with the larger injection intensity ratio is better.

The Fraunhofer far-field diffraction theory and a sectorial screen were used to study the low-order femtosecond vortex beams, theoretically and experimentally. The experimental results show that the frequency component within femtosecond laser can produce destructive interference in the high-frequency area. And the more frequency component is, the stronger the effect becomes. However, it can't change the principal maximum part. So, the sectorial screen can also be used to detect the femtosecond vortex beams. The results also show that the uniformity of the energy distribution can be affected by angles of the sectorial screen. It decreases with the increase of angle. The sectorial screen method was extended to detect the femtosecond vortex beams in this work. It provides a basis for the selection of the best measurement angle. Moreover, the method could be the theoretical and experimental basis for the study on vortex beams from femtosecond amplifiers.

Based on the Richards-Wolf vectorial diffraction theory, the electric and magnetic field components of the focused vortex beams with different states of polarization are derived. The chiral density and superchiral factor are introduced. The effects of the waist radius, polarization state, and topological charge on the local chirality of tightly focused vortex beams are numerically simulated. The numerical results show that the chirality is remarkable when the waist radius of the beam is equal to the focal length of the high numerical aperture lens. The topological charge has a significant effect on the local chirality of tightly focused vortex beams. The radially polarized focused vortex beam has more obvious effect on the local chiral enhancement.

It is necessary to develop a remote and non-contact technology for material composition analysis in metallurgy, nuclear industry and deep space exploration to protect the operator and equipment in hazardous environments from high temperature and strong radiation. The remote Laser-induced Breakdown Spectroscopy (Remote LIBS) technology is a combination of the two key technologies including the long-distance transmission and control of laser and the collection of weak spectra signals, which can be used to obtain the information of target material composition from a distance. In this review, the remote LIBS systems with different optical structures are presented. The characteristics and bottlenecks of them are also compared. To improve the detection sensitivity and distance, the signal enhancement methods for remote LIBS are summarized in this review. The combination of LIBS and Raman technology used in remote sensing is introduced too. Finally, some typical application of remote LIBS such as explosives detection, nuclear industry, deep space detection, etc. are discussed, and the development of remote LIBS in the future is prospected.

A photoacoustic carbon monoxide gas sensor with high sensitivity was demonstrated. A near-infrared distributed feedback laser laser with a wavelength of 1 566.3 nm was used as the excitation source. A commercial fiber amplifier was employed to pump the laser power to 10 W level, which solved the problem of low detection sensitivity due to the weak absorption in the near-infrared wavelength region. A dual channel differential photoacoustic cell with the same structure was designed to reduce the window noise caused by high power laser. By optimizing the excitation light power and working pressure of the sensor system, a signal amplitude of 1.38 mV, a noise (1σ) of 0.96 μV, a detection signal to noise ratio of 1 437.5, the detection sensitivity of 34 ppb, and a normalized noise equivalent coefficient of 1.74×10-8 cm-1W/Hz1/2 were obtained.

The remote Laser-induced Breakdown Spectroscopy (LIBS) technology can be applied to analysis of aviation alloy raw materials in-situ. It provides a new method for online monitoring of aviation industry production. In this work, a coaxial remote LIBS device based on fiber optic spectrometer is developed, and its focus distance can be adjusted from 1 to 30 m continuously. Using the remote LIBS, 6 raw aviation alloy samples with different brands were measured at the distance of 4 m. Then 6 characteristic spectral lines were selected for spectral analysis with K-Nearest Neighbor (KNN) algorithm. The experimental results show that the accuracy of discriminationrate can be up to 98% when the 10 laser pulses deposited on the same ablation point. The accuracy of discrimination rate can be improved to 100% when more than 20 laser pulses deposited on same ablation point. This work can help to discriminate raw materials rapidly and accurately in industrial production site with a remote distance.

In the satellite-to-earth coherent optical communication system, in order to compensate for the wavefront distortion of signal light caused by the random disturbance of atmospheric turbulence, a wavefront coherent compensation technology based on a dual detector array and a stochastic parallel gradient descent algorithm is proposed. Taking the regional light intensity ratio as the beam evaluation standard, an optical communication simulation system integrating signal light wavefront compensation and demodulation is built, and the 65-order Zernike polynomial is used to simulate atmospheric turbulence wavefront distortion. The simulation system adopts quadrature phase shift keying modulation, and the data transmission rate is 10 Gbps. The results show that when the bit error rate is 10-9, the number of photons per bit required by the communication system is reduced to 65.6%, and when the number of photons per bit is 14, the bit error rate is reduced to 2.6%. The wavefront compensation technology based on the dual detector array can compensate the signal light wavefront distortion, reduce the optical communication system error, and provide a guarantee for the signal transmission of the satellite-to-ground optical communication link.

A linearized self-interference cancellation scheme based on a dual-polarization dual-drive Mach-Zehnder modulator is proposed to cancel the self-interference and reduce the nonlinearity of the signal of interest for in-band full-duplex systems. The received signals consist of the signal of interest and self-interference. They are injected into the radio frequency ports of the upper arms of the two sub-dual-drive Mach-Zehnder modulators of the dual-polarization dual-drive Mach-Zehnder modulator, while the constructed reference signals are injected into the radio frequency ports of the lower arms. The two sub-dual-drive Mach-Zehnder modulators are respectively biased at the maximum transmission point and the quadrature transmission point. When the two optical signals from the two dual-drive Mach-Zehnder modulators are detected in two photodetectors, two electrical signals are generated. If the reference signals and the self-interference are the same, the two electrical signals from the photodetectors are self-interference free. The two self-interference-free electrical signals are sampled and further processed in the digital domain to obtain the signal of interest without self-interference and nonlinear components. In addition, an optimization algorithm to reduce the distortion caused by the power mismatch of the two electrical signals is proposed. The feasibility of this scheme is verified by simulations and experiments. The experimental results show that when the signal of interest is a 4-dBm two-tone signal with frequencies of 10 MHz and 12 MHz and the self-interference is a 4-Mbaud quadrature phase-shift keying signal with a center frequency of 11 MHz, a cancellation depth of around 25.6 dB for the self-interference and a cancellation depth of around 17.3 dB for the third-order intermodulation products can be achieved.

In free-space optical communication system, the scintillation of optical intensity from atmospheric turbulence can seriously affect communication performance. In order to reduce the scintillation effect caused by turbulence, based on the time-domain characteristics of light intensity scintillation caused by turbulence, a simulation method which can generate dynamic scintillation series is presented. And its statistical characteristics can be used in the study of free-space optical communication against turbulence effects. In this paper, the time series model are established which can reflect the dynamic characteristics of the received optical intensity. The time series model combine double generalized Gamma distribution and the time signal covariance function of atmospheric turbulence by using generation algorithm of the non-Gaussian colored spectrum signal. When the pointing error is considered in the optical communication system, the time series simulation of the light intensity scintillation under different turbulence conditions is analyzed, and the results are in agreement with the theoretical results. And the formula of average BER under joint probability density is given. The communication system average bit error rate and outage probability can be analyzed by the generated time series involved.

Based on the synthetic method of rainfall attenuation time series, the dynamic rainfall attenuation time series at 28 GHz、30 GHz and 38 GHz in Beijing are simulated, and the power spectraare estimated by using fast Fourier transform and Kaiser Window function. The probability distributions of rainfall attenuation are obtained by simulating rainfall attenuation events for many times and statistical analyzing of the simulation series. Compared with the model recommended by ITU-R, it can be used for the prediction of 5G millimeter wave rainfall attenuation.

1016001Wireless Power Transfer (WPT) and energy harvesting technologies are expected to provide revolutionary technological changes in important fields such as 5G communications and the Internet of Things. The short-range coupling WPT has gradually been commercialized, but there are still many technical bottlenecks in the practical process of microwave power transmission that can realize long-distance applications, such as the contradiction between the limited aperture of transceiver antennas and the WPT efficiency. The developments of electromagnetic metamaterials and metasurfaces have brought new breakthroughs for solving the above-mentioned problems. In this paper, we will focus on the combination of the two important technologies, and systematically review the applications of metamaterials in microwave wireless power transfer and wireless energy harvesting. The results show that the near-field focusing metasurface can significantly improve the transfer efficiency. We will also introduce the research progress of optically transparent metasurfaces and reconfigurable metasurfaces for improving WPT performance and practicability. Based on the periodically close arrangements of subwavelength metamaterial units, a wireless energy harvester with wide-angle incidence and polarization-insensitive characteristics is designed, which can replace conventional receiving antennas with higher harvesting efficiency. Furthermore, coplanar integration with the rectifying diodes makes a new concept of the rectifying metasurface, which can simplify the overall structure, reduce the size, and improve the efficiency. Finally, we will discuss the future progress of WPT, and point out the vital role that programmable and intelligent metamaterial technologies will play very important roles in future simultaneous wireless information and power transfer systems.

The diffractive optical element is designed to correct the aberration on the inner surface of the fairing of 300 mm aperture and three different shapes. The imaging system is also designed and the well imaging quality obtained for ±1° instantaneous field of view and ±20° scanning field of view in the wavelength range of 1.5~1.6 μm.

The surface plasmon device based on single-layer black phosphorous exhibits low light absorption. To address this issue, an anisotropic graphene-black phosphorus heterostructure plasmonicresonator is proposed, and the resonance spectrum and infrared sensing characteristic are studied. The designed graphene-black phosphorus heterostructure and asymmetric Fabry-Perot-like structure can improve the excitation efficiency of surface plasmons. It is found that the absorption of the proposed device can reach to 95.54% and 97.44% along x- and y-directions, respectively, by optimizing the thickness of dielectric layer of optical resonator. In addition, by changing the polarization direction of incident light to dynamically adjust the resonant wavelength, the maximum enhancement factor of 88 and 155 can be achieved for detecting v(COC)s and r(CH2)a modes of polyethylene oxide molecular film with the thickness of 8 nm. The proposed anisotropic device with waveband tunable, high enhancement factor is expected to have the great potential applications in the detection of trace level samples.

Metasurface is composed of many sub-wavelength metastructures that can be fabricated in a flat surface using CMOS process. Light can be precisely controlled by a metasurface through the specificly designed shape and arrangement of metastructures. This enables metasurfaces to realize same funcitons as conventional optical devices. In recent years, metasurface-based flat optic devices have attracted great attention since they are ultrathin, ultralight, mass-producible, and can be monolithically integrated with other optoelectronic devices. Ultraviolet photolithography based wafer-level fabrication has been considered as one of the most promising approaches for the mass-production of metasurface-based flat optic devices. In this article, recent progress in wafer-level metasurface-based flat optics is reviewed. Optical devices such as metalens, polarization bandpass filter, half-wave plate, perfect absorber, and beam deflector are demonstrated on different types of wafers with various diameters.