Abstract:Near-infrared image sensors are widely used in fields such as material identification， machine vision， and autonomous driving. Lead sulfide colloidal quantum dot-based infrared photodiodes can be integrated with silicon-based readout circuits in a single step. Based on this， we propose a photodiode based on an n-i-p structure， which removes the buffer layer and further simplifies the manufacturing process of quantum dot image sensors， thus reducing manufacturing costs. Additionally， for the noise complexity in quantum dot image sensors when capturing images， traditional denoising and non-uniformity methods often do not achieve optimal denoising results. For the noise and stripe-type non-uniformity commonly encountered in infrared quantum dot detector images， a network architecture has been developed that incorporates multiple key modules. This network combines channel attention and spatial attention mechanisms， dynamically adjusting the importance of feature maps to enhance the ability to distinguish between noise and details. Meanwhile， the residual dense feature fusion module further improves the network"s ability to process complex image structures through hierarchical feature extraction and fusion. Furthermore， the pyramid pooling module effectively captures information at different scales， improving the network"s multi-scale feature representation ability. Through the collaborative effect of these modules， the network can better handle various mixed noise and image non-uniformity issues. Experimental results show that it outperforms the traditional U-Net network in denoising and image correction tasks.

Abstract:This paper introduces an innovative Multifunction Integrated Optic Circuit （MIOC） design utilizing thin-film lithium niobate， surpassing traditional bulk waveguide-based MIOCs in terms of size， half-wave voltage requirements， and integration capabilities. By implementing a sub-wavelength grating structure， we achieve a Polarization Extinction Ratio （PER） exceeding 29 dB. Furthermore， our electrode design facilitates a voltage-length product （VπL） below 2 V·cm， while a double-tapered coupling structure significantly reduces insertion loss. This advancement provides a pivotal direction for the miniaturization and integration of optical gyroscopes， marking a substantial contribution to the field.

Abstract:The Fourier transform spectrometer （FTS） is a precision infrared detection instrument. It adopts Michelson interference splitting， and the moving mirror is one of the core components. The uniformity and stability of the moving mirror’s speed directly affect the quality of the subsequent interferogram， so it is necessary to carry out high-precision motion control of the moving mirror. For some FTS with moving mirror in low-speed motion， the traditional M-method can no longer meet the requirements of speed measurement accuracy. In addition， when the moving mirror moves at a low speed， the speed stability is more easily affected by external mechanical disturbance. Based on the stability requirement of the low-speed moving mirror， this paper studies the motion control of the moving mirror based on the T-method measuring speed. It proposes a high-precision algorithm to obtain the measured and expected value of the velocity. By establishing the mathematical model and dynamic equation of the controlled object， the speed feedforward input is obtained， and then the compound speed controller based on the feedforward control is designed. The control algorithm is implemented by the FPGA hardware platform and applied to the FTS. The experimental results show that the peak-to-peak velocity error is 0.0182， and the root mean square （RMS） velocity error is 0.0027. To test the anti-interference ability of the moving mirror speed control system， the sinusoidal excitation force of 5mg， 7.5mg， and 10mg is applied in the moving mirror motion direction on the FTS platform. Under each given magnitude， the scanning of each frequency point in 2~200Hz is carried out. The experimental results show that the peak-peak velocity error and the RMS velocity error are proportional to the excitation magnitude. Under the 10mg excitation， the maximum peak-to-peak velocity error is 0.1405， and the maximum RMS velocity error is 0.0448. After analysis， the speed stability of the moving mirror can still meet the performance requirements of the FTS. This design provides a technical means for realizing the speed control of the moving mirror with low speed and high stability. Also， it makes the FTS have wider applications.

Abstract:Aircraft contrail detection remains crucial for maintaining airspace safety and addressing the greenhouse effects caused by the aviation industry. Existing methods for detecting aircraft contrails primarily relied on the radiance or temperature differences between specific channels in multispectral images. But they did not fully exploit the potential of spectral features. The advancement of satellite-borne hyperspectral imaging technology has provided a new data foundation for aircraft contrail detection. However， methods that rely solely on either the spatial or spectral dimension of the image are unlikely to achieve satisfactory results in the task of aircraft contrail detection using satellite-based hyperspectral imagery. Therefore， a detection algorithm for potential aircraft contrails was explored using shortwave infrared hyperspectral images from the GF-5 AHSI. A spatial-spectral feature extraction method was proposed， which utilized the complementary nature of spatial and spectral information in hyperspectral images. The method achieved an accuracy of over 97% and a false alarm rate of less than 2% on GF-5 hyperspectral image data. It not only provides an innovative technical approach for aircraft contrail detection， but also offers valuable insights for future researchers and promotes further development of hyperspectral imaging in practical applications.

Abstract:Metasurfaces are artificial structures that can finely control the characteristics of electromagnetic waves at subwavelength scales， and they are widely used to manipulate the propagation， phase， amplitude， and polarization of light. In this work， a bound state in the continuum （BIC） structure based on a metallic metasurface is proposed. By adjusting the metallic structure using CST and COMSOL software， a significant quasi-BIC peak can be achieved at a frequency of 0.8217 terahertz （THz）. Through multi-level expansion analysis， it is found that the electric dipole （ED） is the main factor contributing to the resonant characteristics of the structure. By leveraging the characteristics of BIC， an imaging system was created and operated. According to the simulation results， the imaging system demonstrated excellent sensitivity and resolution， revealing the great potential of terahertz imaging. This research not only provides new ideas for the creation of BIC structures but also offers an effective reference for the development of high-performance terahertz imaging technology.

Abstract:A high-performance oxygen detection system enables real-time online monitoring of critical parameters such as oxygen concentration and flow velocity within the engine， ensuring optimal operational efficiency. In flow field tests for engines such as scramjet and aviation engines， the complex environment characterized by high temperatures， pressures， and velocities， along with limited measurement space， poses significant challenges for accurate flow field diagnostics. To address these challenges， a device for measuring oxygen component concentration based on cavity-enhanced absorption spectroscopy （CEAS） was developed. The device features an embedded optical probe design and incorporates multi-directional adjustment mechanisms at both the transmitting and receiving ends to facilitate precise optical path alignment， enhancing its applicability in engineering experiments. Experimental results demonstrated that， in a static environment， the measured oxygen concentration was 20.846±0.97%.. In shock tube experiments， the system successfully captured three distinct states： before the arrival of the incident shock wave， after the passage of the incident shock wave but before the reflected shock wave arrived， and after the passage of the reflected shock wave. The measured oxygen concentration data were consistent with theoretical predictions.

Abstract:Thermo-optic modulators are key components of optical communication systems， and their performance directly affects system efficiency. With the development of silicon optothermonic technology， silicon thermo-optic modulators have been widely used in optothermonic chips. Conventional silicon optical modulators are large in size and have high losses. In recent years， researchers have proposed to use the slow light effect of photonic crystals to reduce the footprint of modulators. Related studies have shown that these devices have advantages， such as small size and low driving voltage. However， the optical transmittance of thermo-optic modulators based on photonic crystals is still affected by defects caused by fabrication errors. Valley photonic crystal optical waveguides can achieve scattering-immune high-efficiency unidirectional transmission， providing a new venue for realizing high-performance photonic devices. In this paper， a new silicon thermo-optic modulator based on a valley photonic crystal Mach-Zehnder interferometer （MZI） is designed. The electrical heating mechanism is introduced on one of the waveguides of the MZI. The thermo-optic effect modulates the refractive index to achieve precise phase modulation of the transmitted light. The thermo-optic modulator device has a small footprint of only 9.26 μm × 7.99 μm， which can achieve a high forward transmittance of 0.91， an insertion loss of 0.41 dB， and a modulation contrast of 11.75 dB. It can also be experimentally fabricated using complementary metal oxide semiconductor （CMOS） technology， so it will have broad application prospects. This modulation principle can be widely used in designing different thermo-optic modulation devices.

Abstract:This paper proposes a novel dual-frequency-band millimeter-wave extended interaction klystron amplifier （EIKA）. It is primarily based on the multimode operating mechanism of dual-2π mode. This design integrates a broadband traveling-standing-wave mode input cavity with a dual-2π standing-wave mode output cavity， resulting in a compact slow-wave structure design that efficiently operates within a total circuit length of approximately 24 mm. Particle-in-cell simulation results reveal that under a 15.6 kV， 1 A electron beam and a uniform 0.6 T magnetic field， the device achieves output power for 183-1024 W across a broadly 1.20 GHz bandwidth， spanning 93.76-94.96 GHz. Remarkably， it facilitates dual-band output in both lower-2π and upper-2π bands， delivering maximum gains of 37.09 dB （1024.10 W at 93.90 GHz） and 35.75 dB （752.20 W at 94.84 GHz）， with -3 dB bandwidths of 0.33 GHz and 0.20 GHz， respectively. The effectiveness for the dual-2π mode design is further confirmed through a cold-test experiment using the perturbation method. This experiment demonstrated typical dual-2π mode field distribution profiles， affirming the design"s efficacy.

Abstract:In this paper， we present a broadband， high-extinction-ratio， nonvolatile 2×2 Mach-Zehnder interferometer （MZI） optical switch based on the phase change material Sb₂Se₃. The insertion loss （IL） is 0.84 dB and the extinction ratio （ER） reaches 28.8 dB at the wavelength of 1550 nm. The 3 dB bandwidth is greater than 150 nm. Within the 3 dB bandwidth， the ER is greater than 20.3 dB and 16.3 dB at bar and cross states， respectively. The power consumption for crystallization and amorphization of Sb₂Se₃ is 105.86 nJ and 49 nJ， respectively. The switch holds significant promise for optical interconnects and optical computing applications.

Abstract:The new active metasurface has the advantages of small size, lightweight and easy integration， so it has an important application prospect in weapon radar intelligent stealth. Based on this, focusing on the requirements of radar intelligent stealth for current weapons and equipment， this paper expounds the methods, approaches and performance advantages of active metasurface in electromagnetic wave regulation， reviews the development history of various active metasurface， and summarizes the research status and future development direction of active metasurface for radar intelligent stealth. It provides the relevant theoretical basis and design reference for the wide application of active metasurface in intelligent stealth of weapon equipment radar.