Fabrication and characterization of back-incident optically immersed bolometer based on Mn-Co-Ni-O thin films for infrared detection

Optically immersed detectors with high index of refraction lenses were an effective technique to improve the performance of thermistor bolometer for infrared detection. In this paper we described the design and fabrication of back-incident optically immersed bolometer with germanium hemispherical lens using the Mn1.56Co0.96Ni0.48O4 thin films prepared by chemical solution deposition method on amorphous Al2O3 substrate. The characteristics of back-incident immersed bolometer operated at room temperature were investigated. It was found that the performance of the detector was significantly enhanced by the use of germanium hemispherical lens. The fabricated bolometer exhibited noise equivalent temperature of 1.56 × 10−7 K/Hz1/2, responsivity of 3.2 × 103 V/W, and detectivity of approximate 9.2 × 108 cmHz1/2/W at 30 Hz. The thermal time constant of 7.3 ms was about one third of the non-immersion ones. Field of view of ±35° and optical immersion gain of up to 14 times were also obtained. The results demonstrated that the feasibility of back-incident optically immersed bolometer could be used to uncooled infrared bolometric applications.