Long wavelength infrared metalens fabricated by photolithography

Metasurfaces in the long wave infrared(LWIR)spectrum hold great potential for applications in ther-mal imaging,atmospheric remote sensing,and target identification,among others.In this study,we designed and experimentally demonstrated a 4 mm size,all-silicon metasurface metalens with large depth of focus opera-tional across a broadband range from 9µm to 11.5µm.The experimental results confirm effective focusing and imaging capabilities of the metalens in LWIR region,thus paving the way for practical LWIR applications of met-alens technology.

Comparative investigation of long-wave infrared generation based on ZnGeP_2 and CdSe optical parametric oscillators

Long-wave infrared （IR） generation based on type-Ⅱ （o→e＋o） phase matching ZnGeP2 （ZGP） and CdSe optical parametric oscillators （OPOs） pumped by a 2.05μm Tm,Ho：GdVO4 laser is reported. The comparisons of the birefringent walk-off effect and the oscillation threshold between ZGP and CdSe OPOs are performed theoretically and experimentally. For the ZGP OPO, up to 419 mW output at 8.04 μm is obtained at the 8 kHz pump pulse repetition frequency （PRF） with a slope efficiency of 7.6%. This ZGP OPO can be continuously tuned from 7.8 to 8.5 μm. For the CdSe OPO, we demonstrate a 64 mW output at 8.9μm with a single crystal 28 mm in length.

Performance Comparison of Long-Wave Infrared Imaging Spectrometer Between Dyson Form and Offner Form

In view of the difficulties in traditional long-wave infrared imaging spectrometer which is hard to realize a high signal-to-noise ratio and miniaturization as well under the weak remote sensing signal,Offner convex grating spectrometer and Dyson concave grating spectrometer,both having concentric structure,are designed and analyzed in the band of 8-12 μm. The diffraction angle expressions of the two spectrometers are obtained and the diffraction characteristics are acquired. Both of the spectrometers are designed in Zemax environment under different F-numbers and different grating constants with the same slit,spatial resolution,spectral resolution and detector. The results show that Dyson grating spectrometer possesses the advantages of higher throughput and smaller volume, and Offner grating spectrometer possesses the advantage of more accessible material and the absence of chromatic aberration. The differences between Dyson form and Offner form show that the former is a better choice in the long-wave infrared imaging spectrometer.

Eye on the Sky: A UAP Research and Field Study off New York’s Long Island Coast

A ten-month field research study was meticulously conducted at Robert Moses State Park (RMSP) on the south shore of Long Island, NY. The objective was to determine if aerial phenomena of an unknown nature exist over a coastal location and to characterize their properties and behaviors. Primary and secondary field observation methods were utilized in this data-centric study. Forensic engineering principles and methodologies guided the study. The challenges set forward were object detection, observation, and characterization, where multispectral electro-optical devices and radar were employed due to limited visual acuity and intermittent presentation of the phenomena. The primary means of detection utilized a 3 cm X-band radar operating in two scan geometries, the X- and Y-axis. Multispectral electro-optical devices were utilized as a secondary means of detection and identification. Data was emphasized using HF and LF detectors and spectrum analyzers incorporating EM, ultrasonic, magnetic, and RF field transducers to record spectral data in these domains. Data collection concentrated on characterizing VIS, NIR, SWIR, LWIR, UVA, UVB, UVC, and the higher energy spectral range of ionizing radiation (alpha, beta, gamma, and X-ray) recorded by Geiger-Müller counters as well as special purpose semiconductor diode sensors.

Very long wave infrared quantum cascade detector based on modular band structure

The optoelectronic performance of quantum cascade detectors(QCDs)is highly sensitive to the design of the energy level structure,leading to the inability of a single structure to achieve broad wavelength tuning.To address this issue,we propose and demonstrate a modular concept for very long wave infrared(VLWIR)QCDs based on a miniband diagonal transition scheme.The modular design makes the wavelength tuning only need to be adjusted for the absorption quantum well module rather than for the whole active region.Theoretical simulation shows that the wavelength tuning range is 39.6 meV(~14–30μm).To prove the feasibility of the scheme,three samples with different absorption well widths were fabricated and characterized.At 10 K,the response wavelengths of the three QCDs are 14,16,and 18μm,respectively,corresponding to responsivities and detectivities exceeding 2 mA/W and 1×10^(10)Jones.

nBn结构长波红外碲镉汞器件优化设计

分析了Type-I型能带对nBn结构碲镉汞器件性能的影响。通过理论计算获得了势垒层组分、掺杂浓度与能带带阶的关系,确定了nBn结构长波器件吸收层掺杂浓度与暗电流的关系。优化了nBn结构长波红外碲镉汞器件的掺杂浓度、势垒层与吸收层之间的组分过渡,建立了二维器件仿真模型并对nBn结构长波红外碲镉汞器件的能带结构进行了计算,结果表明器件结构参数的优化可以有效降低器件工作所需的开启电压,同时在吸收层内几乎不会形成耗尽区,从而有效抑制SRH产生-复合电流及隧穿电流。计算了器件结构参数优化后的长波红外碲镉汞nBn器件暗电流的变温特性,器件工作温度达到110 K以上。为高性能势垒结构长波红外碲镉汞器件的研制提供了理论依据。

变光阑长波红外连续变焦光学系统设计

非制冷长波连续变焦光学系统由于相对孔径大导致小型化和无热化设计困难,本文采用可变光阑约束物镜尺寸压缩系统总长,实现长波640×512非制冷连续变焦光学系统轻小型化设计。通过材料合理配置及主动补偿实现5片透镜的8.5×连续变焦光学系统消热设计。该系统F#恒定1.2、工作波段为8~12μm、视场变焦范围为30°×24°~3.5°×2.8°、系统总长187.5 mm,该连续变焦光学系统重量轻、总长短、透过率高、在-40℃~+60℃温度范围全视场成像质量良好。

大变倍比制冷型长波红外变焦光学系统设计

长波红外变焦光学系统相对于中波红外变焦光学系统存在可用材料少、系统高低温环境无热化难度大等难题。本文采用机械补偿变焦技术实现光学多视场变焦,利用主动补偿的消热差技术使系统在−40°C~+65°C温度范围内能够清晰成像,实现四片透镜架构的制冷型长波红外四视场光学系统设计。该光学系统四视场焦距分别为25 mm、109 mm、275 mm、400 mm,变倍比为15,光学系统包络尺寸为268 mm(长)×200 mm(宽),光学零件总质量为618 g。该光学系统具有质量轻、性能高、成本低等SWaP-C特征,在辅助导航、搜索、跟踪等安防领域中具有较大应用潜力。

Surface-patterned chalcogenide glasses with high-aspect-ratio microstructures for long-wave infrared metalenses

Multidimensional-engineering chalcogenide glasses is widely explored to construct various infrared photonic devices,with their surface as a key dimension for wavefront control.Here,we demonstrate direct patterning high-aspect-ratio microstructures on the surface of chalcogenide glasses offers an efficient and robust method to manipulate longwave infrared radiations.Despite chalcogenide glass being considered soft in terms of its mechanical properties,we successfully fabricate high-aspect-ratio micropillars with a height of 8μm using optimized deep etching process,and we demonstrate a 2-mm-diameter all-chalcogenide metalens with a numerical aperture of 0.45 on the surface of a 1.5-mm-thick As2Se3 glass.Leveraging the exceptional longwave infrared(LWIR)transparency and moderate refractive index of As2Se3 glass,the all-chalcogenide metalens produces a focal spot size of~1.39λ0 with a focusing efficiency of 47%at the wavelength of 9.78μm,while also exhibiting high-resolution imaging capabilities.Our work provides a promising route to realize easy-to-fabricate,mass-producible planar infrared optics for compact,light-weight LWIR imaging systems.

大视场小型无热化长波红外镜组设计

跟随红外镜头小型化、大视场化的趋势,利用ZEMAX设计了一款大视场无热化小型长波红外镜组。系统匹配384×288@17μm的非制冷型长波红外探测器,工作波段为8~12μm。系统F数为1.6,相比于传统红外镜头,视场角更大,全视场达72°,尺寸更小,总长仅为6.96 mm。主镜头仅用3片镜片,通过两种红外光学材料的搭配以及6面非球面实现像差的校正和光学系统的无热化,工作温度范围覆盖-40~60℃。仿真结果表明,在空间频率15 lp/mm处,全视场的调制传递函数大于0.5,空间频率30 lp/mm处,全视场调制传递函数大于0.15。同时为了增大红外探测器的填充因子,提高能量利用率,在系统中搭配设计了放置于红外传感器前的微透镜阵列。实现了红外光学系统的小型化,为红外热像仪在智能手机上的应用提供了解决方案。

LWIR亚波长铝/硒化锌光栅偏振器设计

为提高长波红外偏振成像系统中偏振器件性能,本文通过分析光栅材料及结构参数对光栅偏振性能的影响,设计并优化了一种双层材料构成的亚波长光栅。该光栅为矩形形貌,光栅区由铝与硒化锌构成,两种材料的厚度分别为0.6μm和0.4μm,光栅周期1μm,占空比50%。利用严格耦合波理论分析并计算该结构光栅的衍射效率,7~15μm波段的光以0~60°入射后其0级横磁模透射率达到87.54%以上,消光比超过47 d B。该光栅在10.6μm的测试波长下,TM透射率高达90.80%且具有50 d B以上的消光比,相比槽深相同的单层铝光栅,偏振透过率明显提高。仿真结果显示,该光栅在整个宽长波红外波段具有良好的偏振性能。

深低温工作甚长波面阵红外探测器封装技术

基于甚长波红外探测器对低于液氮温度工作环境的需求,提出了一种深低温工作甚长波红外探测器封装技术。通过对杜瓦组件漏热和芯片电学引出结构的优化设计,可控制芯片在30 K低温工作时整个杜瓦组件的静态热耗为0.65 W,最冷端位置的静态热耗为0.3 W,与之适配的两级脉管制冷机冷量可以满足上述热耗需求。完成了探测器组件的封装测试。结果表明,在制冷机膨胀机热端空气冷却测试条件下,探测器芯片部分可达到35 K的温度;杜瓦的外轮廓小于Φ130 mm×180 mm。该项技术成果促进了深低温工作的甚长波面阵红外探测器封装技术的发展。

Enhanced thermal emission from metal-free,fully epitaxial structures with epsilon-near-zero InAs layers

We introduce a novel method to create mid-infrared(MIR)thermal emitters using fully epitaxial,metal-free structures.Through the strategic use of epsilon-near-zero(ENZ)thin films in InAs layers,we achieve a narrow-band,wide-angle,and p-polarized thermal emission spectra.This approach,employing molecular beam epitaxy,circumvents the complexities associated with current layered structures and yields temperature-resistant emission wavelengths.Our findings contribute a promising route towards simpler,more efficient MIR optoelectronic devices.

长波红外大孔径长焦距无热化光学系统设计

对于长波红外长焦距光学系统,大孔径能使系统具有更好的成像亮度,但也带来了孔径边缘像差较大且难以校正的问题。利用折反射式结构减少光学系统总长,采用两块反射镜结构作为基础,在其后搭配一组校正折射透镜构成光学系统,并应用光焦度分配、消热差及消色差条件,设计出大孔径、长焦距的长波红外无热化光学系统。该光学系统工作波段为8~12μm,焦距为800 mm,全视场角为0.6°,F数为2.5,遮拦比为0.2,光学系统总长为344.62 mm;在-40~60℃工作温度范围内,全视场角的调制传递函数值在奈奎斯特频率20 lp/mm处均大于0.25。设计的长波红外大孔径长焦距光学系统由2块反射镜和4块折射透镜组成,系统结构紧凑,成像性能稳定,可为类似此类光学系统设计提供参考。

紧凑低成本非制冷长波红外连续变焦光学设计

随着红外技术的快速发展,SWaP-C(尺寸小、质量轻、功耗低、成本低)概念已深入红外热像仪整机设计全过程。在非制冷连续变焦红外热像仪设计中,相对已模块化的非制冷探测器与成像电路、光学系统影响整机包络尺寸、产品质量及价格成本,因此设计一款总长短、质量轻、成本低、性能高的非制冷长波红外连续变焦光学系统将具有广阔的市场前景。非制冷长波红外连续变焦光学因相对孔径大、光学材料种类少等因素存在系统小型化和无热化设计难题,通过采用变F#设计方法约束物镜尺寸;利用三组联动变焦技术平衡像差、压缩系统总长;通过主动补偿的消热差技术使得系统在-40~+60℃温度范围成像质量良好,实现四片透镜构成的非制冷长波红外连续变焦光学系统设计。该系统工作波段为8~12μm,焦距变化范围为20.7~126 mm,对应F#为1.05~1.2,视场变化范围为21°×16.8°~3.5°×2.8°,变倍比为6.0×,最大物镜直径116 mm,光学系统总长180 mm,光学零件总质量418 g。该光学系统具有轻小型、高性能、低成本等SWaP-C特征,将在无人装备平台及手持热像仪设备中得到广泛应用。

长波红外高透射率二维光子晶体设计及应用研究

近年来,如何提高红外探测器的光子吸收率是目前红外探测的重点研究之一,增加入射光的透射率是其中重要的一环。传统的多层减反膜受到粘附性,热失配和稳定性不足等问题在应用上受到一定限制。光子晶体是一种直接在光学表面加工微结构实现增透效果,不存在上述等问题,并且表现出较好的增透效果。但目前光子晶体设计结构复杂,对工艺加工带来困难。基于此本文设计了几种简单的ZnS光子晶体几何结构,包括长方体、圆柱体、六棱柱体和金字塔结构,在长波红外8~10μm波段内每种光子晶体结构的最佳平均透射率均在90以上,其中金字塔的增透效果最好。设计了金字塔阵列结构,透射率仿真结果表明金字塔阵列间隙在一定范围内均能保持98以上的透射率。最后探究了不同基底材料碲镉汞厚度和温度对光子晶体透射率的影响。本文研究可为光子晶体增透研究和微纳光学器件设计提供一定的借鉴意义。

聚乙烯分子结构长波近红外–中红外光谱研究

采用长波近红外–中红外光谱对聚乙烯分子结构进行了研究,结果表明,聚乙烯分子结构的红外吸收模式主要包括2νas(CH_(3))、2νas(CH_(2))、νas(CH_(2))+ν(CH)、2νs(CH_(3))、νas(CH_(2))+νs(CH_(2))、2νs(CH_(2))、νas(CH_(3))、νas(CH_(2))、νs(CH_(3))、νs(CH_(2))、δ(CH_(2))和ρ(CH_(2))。采用变温长波近红外–中红外光谱进一步开展了聚乙烯分子的热稳定性研究,结果表明,在303~393 K,聚乙烯分子的吸收频率及强度都有明显改变。

基于碲化铋纳米线的长波红外光热电探测器

研究碲化铋(Bi_(2)Te_(3))光电探测器在长波红外波段的响应机制及性能提升策略对光电探测的发展具有重要意义。首先通过化学气相沉积(CVD)中生长温区的选择,实现了热力学主导的纳米结构形貌可控合成,其形状从三角形纳米片转变为纳米线。然后研究了Bi_(2)Te_(3)纳米线光电探测器在长波红外波段的响应,确定其响应机制由光热电效应主导。通过优化电极材料,将探测器响应度提升至17 V/W,噪声等效功率为0.22 nW·Hz^(-1/2);通过构造非对称电极结构,解决了微纳型光热电探测器在全局光照明下无响应电压输出的问题。此外,Bi_(2)Te_(3)纳米线光热电探测器响应时间为53μs,突破了传统热型光电探测器毫秒级响应速度的限制。与其他复杂的结构设计相比,Bi_(2)Te_(3)纳米线光电探测器有与之相当的性能,为二维材料光热电探测器的设计提供了新的思路。

红外图像融合在光电侦察系统中的应用

针对光电侦察系统中长波波段与中波波段图像融合问题,开展红外图像融合仿真及应用研究。首先分析侦察目标辐射特性在不同波段的异同,其次设计图像融合算法流程,最后进行仿真及试验。结果表明,图像融合匹配准确,融合结果可以将不同波段的图像优势特性相结合。

短工作距无热化长波红外检测镜头设计

针对1 024×1 024长波非制冷探测器的应用需求,设计了一款短工作距高分辨率8~14μm波段长波红外检测镜头。该镜头采用了一个非球面提高了光学元件的校正像差能力,减少了镜片数量;为满足在-45℃~70℃的温度范围内的无热化要求,在光学系统中加入了衍射面,使其在40 lp/mm处的MTF均大于0.2。该镜头畸变小于1.5%,成像质量良好,结构紧凑,满足了在短工作距离范围内的高分辨率检测,具有较广泛的应用价值。