Performance of achromatic Si-based metalens for LWIR uncooled IRFPA

Compact and low-cost sensors are required for long-wavelength infrared (LWIR) regions and lens is a key component to realize them. In recent years, we have been developing Si-based metalens for our uncooled infrared focal plane arrays (IRFPAs). However, the previous metalens is chromatic and only designed for the wavelength of 10 µm. In this study, we designed an achromatic metalens that matches focal lengths for wavelengths ranging from 8 to 12 µm, with intervals of 1 µm and fabricated the metalens on a Si wafer. We adapted the metalens on our infrared sensor and evaluated thermal images and responsivity. We confirmed a significant reduction in chromatic aberration for the developed achromatic metalens. The knowledge gained in this study will contribute to establish a design guideline to improve our metalens.