Designing Optically & Utilization of Thermopile Chip with Resonant Cavity Absorber Structure as IR Absorber

Abstract

This paper presents a novel thermopile chip in which the resonant cavity structure was fully utilized as an absorber by an optical design. The resonant cavity absorber structure was designed using Al as anthe bottom reflective metal layer, air as the intermediate dielectric layer, and SiO2/TiN/Si3N4 sandwich layers as the top absorption layer, while the bottom reflective metal (Al) was deposited on the cold junctions of the thermopile. The simulation and calculation results show that the thermopile chip with resonant cavity absorber structure not only has great infrared absorption in the wide infrared absorption range but also can effectively prevent the cold junctions from absorbing infrared radiation and inhibit the rise of temperature. As a result, the temperature difference between the hot junctions and the cold junctions is increased, and the responsivity of the thermopile chip is further improved. Moreover, the duty cycle of the thermopile chip is greatly improved due to the double-layer suspension structure. Compared with the traditional thermopile chip structure, the sizes of the thermopile chip with the resonant cavity absorber structure can be further reduced while maintaining responsivity and specific detectivity.