The terahertz imaging is mostly detected by the pyroelectric method which put forward high requirements on the average terahertz power generated by terahertz source. According to recent studies, a terahertz imaging method based on quantum tunneling is proposed. In this method, the generated photoelectron is related to the peak electric field of the incoming terahertz radiation. By designing the resonant properties of the structured metallic layer or layers in the terahertz range, narrowband and broadband detection of terahertz radiation is possible. Also, by engineering the field enhancement properties of the structured metallic layer the sensitivity range of the terahertz detector may be changed. In this paper, the terahertz antenna structure is designed by COMSOL and CST for a certain terahertz frequency band (0.14 THz). The optimal structure with structure period is about 200 μm is obtained through modeling and simulation. Meanwhile, other structure parameters such as line width and gap width (100 nm) are obtained. The simulation results show that the local electric field strength can reach 108 V/m. Combined with the simulation results and the actual preparation capability, the terahertz antenna is prepared by nanoimprint lithography and Ion Beam Etching (IBE). Here, the preparation process of terahertz antenna is briefly introduced and preliminary preparation results are given.
Augmented reality technology is a technique that combines virtual information with the real world, providing an enhanced perception and interactive experience by overlaying virtual content in the user's field of view. In augmented reality technology, surface relief gratings are widely used in optical projection systems to achieve precise positioning and accurate projection of virtual images. In this study, we first designed surface relief gratings in three regions - coupling, turning, and output based on the rigorous coupled-wave analysis. Then, by gradually optimizing parameters such as duty cycle, tilt angle, and depth of the gratings in each region. We ultimately achieved overall structural optimization with respect to uniformity and optical efficiency. This research provides valuable guidance for further exploration of micro/nano structures in the field of augmented reality.
The innovation of this paper is combining the micro-nano optical technology and the vacuum photoelectric imaging devices manufacturing. The multialkali photocathode deposition substrate is designed with a meta-surface structure by using the Finite-difference time-domain. According to the nanoimprinting and the atomic layer deposition, the structure of meta-surface can be obtained. Metasurface have the ability of simultaneously controlling the phase of the light by tailoring the geometry of microstructures. The negative loss in the direction of light wave propagation is suppressed, the reflection at the interface between the cathode and the deposited substrate is reduced, and the absorption coefficient of the cathode material to the incoming light is improved. And the absorption rate of the incident light can be increased by 20.5%. The atomic layer deposition is used to prepare the nanolaminate on the surface of the micro-structure. Based on the imaging tube with the meta-surface, the experiment results show that the average value of the quantum efficiency increased by 21.2% in the visible light range and increased by 10.3% in near infrared band respectively, which reaching the international advanced level. A new method is provided to improve the performance parameters of the vacuum photoelectric imaging devices and point the direction for the improvement of the imaging tube. As shown in this paper, the performance parameters of the vacuum photoelectric imaging devices still have great development potential by optimizing the structure of the meta-surface.
The image intensifier is the core component of all kinds of low-light-level night vision devices, which are widely used in security, medicine, biology, and other fields of detection and imaging devices. Multialkali photocathode is one of the important parts of the image intensifier photoelectric conversion. Its optical constant and thickness will affect the sensitivity of the image intensifier. The photocathode material is a chemically active alkali metal (Na2KSb (Cs)). When the photocathode is removed from the high-vacuum alkali source environment of the image enhancement tube, its properties will change. Therefore, it has been impossible to directly measure the optical constant and thickness of the photocathode. In this paper, we established the photocathode optical model with the help of the Snellmeier dispersion model. The optical constants and thickness of the photocathode in the visible band 380nm-780nm are obtained for the first time by the full-spectrum fitting method. The deviation between the fitted value and the measured value is 0.03%, which is in good agreement. The optical constants and thickness of the photocathode obtained in this paper can provide more accurate guidance for the optical system design of image intensifiers. In addition, the method can be extended to the analysis of optical properties of other easily oxidized thin film materials by changing the dispersion formula, which has practical significance in the fields of vacuum optoelectronics and optical thin films.
Micro-nano structure applied to photoelectric fields were made on high borosilicate glass by the MEMS process. This paper discussed the transmittance characteristics of micro-nanostructures by analyzing the transmittance of high borosilicate glass with different surface states and combining them with the theoretical analysis results. The transmittance of high borosilicate glass with different surface states was tested by an ultraviolet-visible spectrophotometer in the range of 400–850 nm. Through testing and comparison, it is found that the micro-nano structure makes the transmittance of high borosilicate glass obviously different in the test band. The average transmittance has been down 68%, and micro-nano structure can achieve anti-reflection in the specific band. Therefore, through matching the micro-nano structure with the photoelectric materials, the incident light could occur total reflection at the interface between the photoelectric materials and vacuum. Micro-nano structure can improve the utilization rate of light energy.
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