Li Fangzhe, Deng Jie, Zhou Jing, Chu Zeshi, Yu Yu, Dai Xu, Guo Huijun, Chen Lu, Guo Shangkun, Lan Mengke, Chen Xiaoshuang
State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2020 Apr 14;10(1):6372. doi: 10.1038/s41598-020-62433-w.
Polarization-independent dielectric meta-lens is proposed to monolithically integrate with a HgCdTe infrared photodetector to concentrate power flux into a reduced photosensitive area for performance enhancement. Although a reduction in photosensitive area could suppress the dark current, the more seriously reduced light absorptance would degrade the specific detectivity D. The integration of the meta-lens could reverse the situation by improving the absorptance of the photosensitive region. The meta-lens composed of an array of nano-pillars with varying diameters is formed by carving the CdZnTe substrate of the HgCdTe detector so that the integration could be accomplished in situ. The meta-lens focuses the incident light through the CdZnTe medium and at the HgCdTe photosensitive region. The focal spot is about the wavelength size and the focusing efficiency is above 63%. Concerning a HgCdTe detector with a pitch size of 40 μm × 40 μm, when the photosensitive area is reduced to 5 μm × 5 μm, the meta-lens could still keep the light absorptance above 50%, which is 49 times higher than that of the device without the meta-lens. The dark current reduces with the decreasing photosensitive area in a linear manner. When the photosensitive area shrinks from 40 μm × 40 μm to 10 μm × 10 μm or 5 μm × 5 μm, the dark current reduces by 16 or even 64 times. Compared to the pristine device, the employment of the meta-lens together with the reduction in photosensitive area could enhance D by 5.5 times for the photosensitive area as 5 μm × 5 μm. Further, the meta-lens exhibits a good dispersion tolerance over the wavelength range from 3.3 μm to 5 μm. The averaged detectivity enhancement over this spectrum range is around 3 times for the photosensitive area as 5 μm × 5 μm. The angular response of the meta-lens integrated detector depends on the focal length. For a focal length of 73 µm or 38 µm, the angle of view for a 5 μm × 5 μm photosensitive area is 4.0° or 7.7°. For the inter-pillar distance to be 2 µm in our design, the influence of the coupling effect between the nano-pillars on the performance of the meta-lens is little.
提出了一种与碲镉汞红外探测器单片集成的偏振无关介质超透镜，用于将光通量集中到减小的光敏区域以提高性能。虽然减小光敏区域可以抑制暗电流，但光吸收率的更严重降低会降低比探测率D。超透镜的集成可以通过提高光敏区域的吸收率来扭转这种局面。由不同直径的纳米柱阵列组成的超透镜是通过雕刻碲镉汞探测器的碲锌镉衬底形成的，从而可以原位完成集成。超透镜通过碲锌镉介质将入射光聚焦到碲镉汞光敏区域。焦点约为波长尺寸，聚焦效率高于63%。对于间距尺寸为40μm×40μm的碲镉汞探测器，当光敏区域减小到5μm×5μm时，超透镜仍可使光吸收率保持在50%以上，这比没有超透镜的器件高49倍。暗电流随光敏区域的减小呈线性降低。当光敏区域从40μm×40μm缩小到10μm×10μm或5μm×5μm时，暗电流降低16倍甚至64倍。与原始器件相比，对于5μm×5μm的光敏区域，超透镜与光敏区域减小一起使用可使比探测率提高5.5倍。此外，超透镜在3.3μm至5μm的波长范围内表现出良好的色散容限。对于5μm×5μm的光敏区域，在此光谱范围内的平均探测率增强约为3倍。超透镜集成探测器的角响应取决于焦距。对于73μm或38μm的焦距，5μm×5μm光敏区域的视角为4.0°或7.7°。在我们的设计中，当柱间距为2μm时，纳米柱之间的耦合效应对超透镜性能的影响很小。
