The metasurface is an ultra-thin two-dimensional planar array that enables multi-functional and extraordinary electro-magnetic control. It consists of structural units of metamaterials which can flexibly and effectively control the phase, polarization mode and propagation mode of electromagnetic waves. Therefore, it shows great potentials and prospects in various applications including the controllable “smart” surfaces, novel waveguide structures, electromagnetic wave absorption and the miniaturized cavity resonators. In this review, we first introduce basic concepts and background of metasurfaces, and then summarize the design and development of several absorptive metasurface devices in the infrared & terahertz (THz) bands and finally discuss its potential problems and prospective in future.

Mid-infrared Er:ZBLAN fiber laser emitting at the wavelength of 3 μm is widely used in industry, medicine, military and other fields due to its advantages such as good beam quality, small size, coiling-ability and easy realization. In this paper, the development status of Er:ZBLAN fiber laser is introduced. The technical difficulties encountered in the development of Er:ZBLAN fiber laser are discussed. Moreover, their future development directions are also summarized and prospected. According to the current research situation, it is proposed that multi-stage amplification will be a method to further improve the single laser power of 3 μm Er:ZBLAN fiber laser. In order to breakthrough the power limit of single laser, the integration of single laser and fiber beam combination technology will become a research direction in the future.

The tilt mirrors and deformable mirrors in adaptive optics system are usually using piezoelectric ceramic actuators for precise displacement, however, piezoelectric ceramic actuators own obviously nonlinear hysteresis effect which affects the positioning performance of the system. In order to compensate the hysteresis, there is a need to model hysteresis effects. In this paper, hysteresis operator is introduced and using Bayesian regularization training algorithm to train BP neural network to construct hysteresis model of piezoelectric ceramic actuator, an experimental study was conducted on a piezoelectric actuator developed by Institute of Optics and Electronics, Chinese Academy of Sciences. The final experimental results show that the hysteresis model of piezoelectric ceramic actuators constructed by BP neural network has more accurate identification capability. The relative error of the positive model is 0.0127 and the relative error of the inverse model is 0.014. The nonlinearity of the piezoelectric Displacement/μm actuators has been reduced from 14.6% to 1.43%.

With the increasing demand for high resolution, high speed transmission and low power dissipation in space remote sensing, TDICMOS detector based on charge accumulating will become an important part of video detectors. No matter in process or in structure, the detector is essentially different from the traditional TDICCD and CMOS detector with digital accumulating. Therefore, many original methods for testing the performance parameters of the detector cannot be applied to the TDICMOS detector based on charge accumulating. This paper proposes the test methods of charge-DN factor, full well charges, transfer efficiency, readout noise based on TDICMOS characteristics. We also verify these test methods by experiment, prove the correctness of these testing methods and the feasibility of the engineering. The results provide important basis for the application of TDICMOS camera in the future.

An oblique incidence dynamic phase-shifting interferometer based on inclination angle deflection is proposed to quickly obtain the surface distribution of optical surface with flatness of micron dimension. A 2×2 point source array is introduced into a Michelson interference system, and the incidence angle of each point source on the interferometer cavity is adjusted precisely to induce equal phase shift. Spatial separation is realized in combination with a lens array. The four phase-shifting interferograms are captured simultaneously on a single CCD, thereby realizing dynamic measurement. The flatness of a 35 mm aperture silicon wafer is measured at oblique incidence angle of 68°, the root mean square (RMS) is 1.631 μm and peak-to-valley (PV) is 9.082 μm. The experimental results indicate that the proposed interferometer overcomes the disturbance of vibration environment and extends the measurement range of interferometer with high precision by introducing the simultaneous phase-shifting interferometry based on inclination angle deflection into the oblique incidence interference system.

A terahertz broadband tunable reflective linear polarization converter based on oval-shape-hollowed graphene metasurface is proposed and verified by simulation and Fabry-Perot multiple interference theory in this paper. Our designed metasurface model is similar to a sandwiched structure, which is consisted of the top layer of anisotropic elliptical perforated graphene structure, an intermediate dielectric layer and a metal ground plane. The simulation results show that when the given graphene relaxation time and Fermi energy are τ=1 ps and μc=0.9 eV, respectively, the polarization conversion rate (PCR) of the designed metasurface structure is over 90% in the frequency range of 0.98 THz～1.34 THz, and the relative bandwidth is 36.7%. In addition, at resonance frequencies of 1.04 THz and 1.29 THz, PCR is up to 99.8% and 97.7%, respectively, indicating that the metasurface we designed can convert incident vertical (horizontal) linearly polarized waves into reflected horizontal (vertical) linearly polarized waves. We used the Fabry-Perot multi-interference theory to further verify the metasurface model. The theoretical predictions are in good agreement with the numerical simulation results. In addition, the designed metasurface reflective linear polarization conversion characteristics can be dynamically adjusted by changing the Fermi energy and electron relaxation time of graphene. Therefore, our designed graphene-based tunable metasurface polarization converter is expected to have potential application value in terahertz communication, sensing and terahertz spectroscopy.

In order to realize the online detection of laser shock processing and aim at the phenomenon of laser-induced plasma acoustic wave, the SIA-AEDAC-01 acoustic emission acquisition card is used to collect acoustic wave signals. The real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal is studied and designed. The test experiment for feasibility and accuracy of the system is designed. Firstly, the laser-induced plasma acoustic wave signal propagating in air is collected by the online detection laser shock processing system, and then the system gets the laser-induced plasma acoustic wave signal energy. The residual stress of the test pieces after the treatment of laser shock processing was measured by an X-ray stress analyzer to verify the reliability. The experimental results show that the laser-induced plasma acoustic wave signal can be collected and analyzed in real-time by the real-time acquisition and analysis software system, which is designed and developed in this work, and the software system can accurately get the acoustic signal energy. At the same time, both the acoustic wave signal energy and the surface residual stress of the test pieces are increased with the laser energy, and their change curve is consistent. In conclusion, the real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal can satisfy the requirements of online detection of laser shock processing with accurate and reliable performance, and meet the online monitoring requirements of laser shock processing.

A focusing structure which can achieve negative refraction and dual subwavelength imaging is proposed, which is based on two-dimensional (2D) photonic crystal (PC) which consisting of air holes in silicon. The light radiated from a point source can form two images through a triangular PC. The transmittance of light is increased and the side spot at image2 is eliminated by adding the gratings on the sides of the PC. When the air slit of gratings is w=0.76a and the distance between gratings and PC is dg=0.1a, the minimum half-width of the image1 reaches 0.433λ, the maximum half-width of image2 reaches 0.842λ, which are both lower than incident wavelength. In addition, the PC realizes wide-spectrum dual subwavelength imaging when the incident wavelength varies from 3.19a to 3.26a. The position formulas between images and point source are also demonstrated. Based on the results, we propose a new confocal system based on PC that can achieve subwavelength imaging.

In this paper, a femtosecond green laser with wavelength of 515 nm was used to process the AZ31 magnesium alloy. The laser ablation threshold and ablation rate of Mg alloy were calculated. The mechanism of femtosecond green laser process was determined. The effects of surface microstructures on corrosion rate of AZ31 magnesium alloy was compared and analyzed. The results show that the laser ablation threshold of AZ31 magnesium alloy is 1.46 J/cm2, the ablation rate is 0.68 μm/pulse in the laser fluence of 8.36 J/cm2, the ablation rate increases with the laser fluence increasing. The high-quality holes can be fabricated with the laser fluence of 8.36 J/cm2 and the pulse number of 1000. In terms of the corrosion rate of magnesium alloy, the groove structure is less than that of the columnar structure and less than that of the smooth surface, among which the corrosion rate on the microstructural surface is about 1/3~1/2 of that on the smooth surface in 24 hours.

A regionally controllable super hydrophobic/super hydrophilic mixed surface was prepared by laser ablation, and the effects of pre-wetting on the surface wettability of samples under water and oil were studied, as well as the stability of the surface wettability of samples. The results show that pre-wetting can change the oil contact angle underwater and water contact angle under-oil on the sample surface, and also change the behavior of bubbles on the surface. After the samples were soaked in water, heated or exposed to air, the super hydrophilic surface showed wettability transformation while the super hydrophobic surface was relatively stable. The sample can maintain long-term stability sealed dry preservation at room temperature. The results are of great significance for oil-water separation, oil-gas separation and bubble control in aqueous media.