Study Of In Sb Mid-infrared Polarization Detector Based On Metamaterials

Polarization is another field of light besides intensity,wavelength and coherence,which can indicate different properties determined by the object,such as surface characteristics,roughness,shadows,shape,etc.Therefore,infrared polarization detection can obtain target polarization information,distinguish the inherent polarization characteristics of artificial targets and backgrounds,and improve the detection and identification of targets.Therefore,infrared polarization detection can obtain target polarization information,distinguish the inherent polarization characteristics of artificial targets and backgrounds,and improve the detection and identification of targets.Meanwhile,the state-of-the-art micro and nano processing technology and infrared detector preparation technology make it possible to fabricate mid-infrared polarization detectors for tabletop integration process.In this paper,we design and prepare a monolithic integrated subwavelength metal grating InSb infrared polarization detector for mid-wave infrared band polarization detection characteristics by theoretical simulation and experimental verification methods,core content and innovation points are:（1）Based on the material structure and operating band of the InSb detector and the excellent polarisation properties of the sub-wavelength metal grating,a metamaterial-based InSb mid-infrared polarisation detector has been designed.The polarisation optical properties of coupled subwavelength metal gratings and InSb detectors are systematically investigated using the time-domain finite-difference method.The structural parameters of an aluminium grating for InSb mid-wave infrared polarisation detectors are defined to achieve high TM-wave transmittance and extinction ratio.The results show that the period of the sub-wavelength metal grating is the main factor affecting its polarisation performance;the duty cycle and the height of the metal wire grating need to be controlled within a range of variation so that the TM-wave transmittance and extinction ratio of the sub-wavelength metal grating both reach a certain height value and maintain good performance.Finally,combined with the process conditions,the sub-wavelength grating parameters are determined:grating material Al,grating period 300nm,thickness 100nm,duty cycle 0.5.（2）The mid-wave infrared band polarization test system was designed and built to be able to test the polarization performance of the InSb polarization detector.Based on the theoretical analysis,an InSb IR polarisation detector with an integrated sub-wavelength metal grating was prepared using the electron beam exposure technique,and the grating microscopic morphology was characterised by SEM.At 3.85μm and-0.1V（77K）,the four angularly polarised image elements exceeded 1.53E+10cm Hz^1/2/W.Finally,the basic shape of the polarisation transmittance curve in the mid-wave infrared band was obtained by combining the polarisation test system.（3）A broad-spectrum circularly polarized device is proposed and simulated to be designed.The circularly polarized device has a cascaded cavity structure with efficient discrimination capability in the 3.85μm band,which can effectively block right-handed circularly polarized light and allow left-handed circularly polarized light to pass smoothly.Meanwhile,the circularly polarized device has a simple structure and can be prepared using the same platform and process as that of subwavelength metal gratings.The effects of each parameter of the circular polarizer on the performance of the polarizer are investigated by numerical simulations,and the optimal parameters of the circularly polarized device are obtained.The numerical simulation results show that the transmittance of the left circularly polarized light is 92%at a wavelength of 3.85μm,and the circular dichroism is 91.98%with good circular polarization selection performance.