亚波长金属线栅的设计、制备及偏振成像实验研究

Design and fabrication of sub-wavelength metal wire-grid and its application to experimental study of polarimetric imaging

针对红外偏振成像系统,运用等效介质理论,在氟化钙基底上设计了周期为200nm,深度为100nm的金属铝栅.模拟计算结果表明,设计的金属铝栅在中红外(3—5μm)和远红外(8—12μm)双波段范围内,以及±20°的视场范围内能够提供大于35dB的消光比.利用电子束曝光、反应离子束刻蚀、等离子去胶等工艺完成了金属铝栅的制作.将金属铝栅放在中波红外热像仪前,得到了目标轮廓清晰的偏振图像.

Metal wire-grid whose period is far less than the illuminating wavelength exhibits strong polarization selectivity within a large field of view over a wide wave length range. Thus it could be used as the polarization-controller in the polarimetric imaging system. For infrared polarimetric imaging system,an aluminum wire-grid on the CaF substrate with period of 200nm and depth of 100nm was designed based on effective medium theory. The calculation results demonstrate that the designed wire-grid has the extinction ratio larger than 35 dB within a field of view ± 20° over both middle wave infrared （MWIR） （3—5 μm） and long wave infrared （LWIR） （8—12 μm）. The aluminum wire-grid was fabricated by electron beam lithography,reactive ion etching and plasma stripping. A clear-cut polarimetric image was obtained when wire-grid was placed in front of a MWIR thermal infrared imager.