固体浸没式红外超表面透镜设计

Design of solid-immersion infrared metalens

红外焦平面阵列在各类红外成像系统中发挥着巨大的作用。为提升红外焦平面的工作温度、量子效率和灵敏度,通常使用微透镜阵列作为红外焦平面的聚光器。当前微透镜阵列的制作材料通常与红外探测器材料不同,因此在集成装配时需要额外的工艺手段,工艺难度较大且效率较低。利用微纳光学超表面技术体系,可以在红外探测器衬底材料上直接制作平面式的固体浸没型微透镜阵列,实现前置微透镜与红外焦平面的单片集成。文中以红外探测领域最有潜力的锑化物Ⅱ类超晶格红外探测器为应用目标,设计了一种基于GaSb衬底的固体浸没式红外超表面透镜。设计的超表面透镜在中波红外波段工作,能适用于所有入射偏振。器件设计焦距为100μm,理论上在目标波长下的最高聚焦效率达到70.7%,数值孔径(NA)达到1.15。该设计可以推动微透镜阵列向扁平、超薄、轻量的方向发展,简化微透镜阵列与红外焦平面阵列的集成工艺,有望提升红外焦平面的探测效率,并降低制造成本。

Infrared focal plane arrays(IR FPAs) play an important role in various infrared imaging systems. In order to improve the working temperature, quantum efficiency and sensitivity of IR FPAs, microlens arrays are usually used as light condenser for IR FPAs. Currently, materials of microlens array are usually different from the material of the infrared detector, so additional process means are required during integration of the two parts,which is difficult and inefficient. Based on metasurface, a planar solid immersion microlens array can be directly fabricated on the substrate material of the infrared detector, so that monolithic integration of the two can be realized. Aiming at the application of antimonide class type Ⅱ superlattice infrared detector, a solid immersion infrared metalens based on GaSb substrate this was designed. The designed metalens worked in the mid-wave infrared band and could be applied to all incident polarizations. The designed focal length is 100 μm for all metalens devices designed here. Theoretically, the highest focusing efficiency at the target wavelength reaches70.7%, and the numerical aperture(NA) reaches 1.15. This design can promote microlens array to be flat, ultrathin and lightweight, simplifying the integration process of microlens array and infrared focal plane array.Besides, this design is expected to improve the detection efficiency of infrared focal plane device and reduce manufacturing cost.