大气红外波段的片上集成式偏振光谱成像器件

On-chip integrated polarization spectral imaging device for atmospheric infrared band

红外探测与遥感是气象观测的核心技术,红外辐射探测仪作为气象卫星的重要载荷,主要用于大气温度、湿度的定量化探测,其探测精度取决于光谱和偏振测量的通道数。常见的技术方案是通过组合滤光片与偏振片转轮实现光谱和偏振的探测,这造成了系统体积大、功耗高、通道数少的问题。发展片上集成式偏振光谱成像器件是解决上述问题的有效方法,已有研究主要采用薄膜谐振腔或共振微结构的阵列化方案,但二者都无法兼顾光谱和偏振选择的要求。有鉴于此,提出了一种基于薄膜微结构耦合调控的设计新思路,以13μm附近的大气红外波段为例,实现了片上集成式的偏振光谱成像,6个通道的平均透过率和消光比分别达到了94%和30。该器件有望在将来被广泛应用于偏振光谱成像领域中,同时,由于该器件对基底折射率并不敏感,基底的选择也会更加自由。

Objective Infrared detection and remote sensing are the core technologies of meteorological observation.As an important payload of meteorological satellites,infrared radiation detectors are mainly used for quantitative detection of atmospheric temperature and humidity.Their detection accuracy depends on the number of spectral and polarization measurement channels.The common technical solution is to achieve spectral and polarization detection by combining filters and polarizer wheels,which leads to problems such as large system volume,high power consumption,and few channels.The development of on-chip integrated polarization spectral imaging devices is an effective method to solve the above problems.Previous studies have mainly used arraying schemes of thin film resonant cavities or resonant microstructures,but both cannot meet the requirements of spectrum and polarization selection.To solve these problems,this article proposes a new design approach based on coupling regulation of thin film microstructures,which can provide an on-chip integrated polarization spectral imaging device.Methods An on-chip integrated polarization spectral imaging device based on thin film microstructure,which combines a subwavelength grating broadband reflector and a multi-layer high reflection film is built in this paper(Fig.1).By constructing matching conditions for phase and amplitude at the interface between multilayer films and microstructures,narrow band transmission peaks with polarization selective characteristics can be excited through the coupling of them(Fig.2).Specifically,firstly one can design a broadband high reflectivity microstructure with a central wavelength ofλ0,then design a high reflection film stack centered onλ0,with the outermost layer being a low refractive index interlayer,next adjust the appropriate spacing layer thickness Dspacer to make a narrow band transmission peak appears near the centerλ0,last scan the transmission spectrum with changes in scanning period and duty cycle,find the parameter combination corresponding to the peak,and achieve multi-channel design(Fig.3).Meanwhile,by changing the lateral parameters of the microstructure,multichannel polarization filtering can be achieved at different wavelengths,thus enabling on-chip integrated spectral imaging(Fig.4).Results and Discussions Taking the atmospheric infrared band around 13μm as an example,an on-chip integrated polarization spectral imaging device with 6 channels is designed,the average transmittance of them is over 94%and the extinction ratio is about 30(Fig.6,Tab.1).In addition,research and exploration on the physical mechanisms(Fig.5)and fabrication schemes of the devices(Fig.7)are also conducted.Meanwhile,as the device is not sensitive to the refractive index of the substrate,the selection of the substrate could also be more flexible.This new design approach has opened up new doors for on-chip integrated spectral imaging devices.With the improvement of fabrication technology and further optimization of structure,it is expected to achieve better performance and be successfully applied in the field of polarization spectral imaging.In addition,in recent years,some low dimensional infrared detection materials such as GaSb nanowires have also shown excellent infrared detection performance,and due to their dimensional advantages,they can achieve the detection of polarized infrared light.Assigning spectral selection function to infrared detection materials with polarization selective properties will also be a new research approach in the future.