Thermopile Detector Radiation Hardened Readout

Thermopile detectors have some desirable characteristics that make them better suited for certain applications than bolometers and pyroelectric/ferroelectric detectors. They are passive devices, require no electrical bias, and generate a voltage output that is proportional to the input radiation signal. They are also typically uncooled and are insensitive to substrate temperature variations, making temperature stabilization unnecessary. They are highly linear, which combined with their insensitivity to substrate temperature, make them ideal for accurate radiometry. Finally, they require no optical chopper and they have negligible 1/f noise, provided the readout amplifier has high input impedance. These properties make them well suited for broadband spectral detection applications. A two-dimensional thermopile array built over CMOS readout circuitry in the substrate will allow large format staring imaging arrays with low 1/f noise for radiometric applications.

The technology developed on this SBIR will create an improved thermopile readout to meet broadband infrared data collection in space. Thermal detectors (such as thermopiles), while typically less sensitive than quantum detectors, are useful when the combination of long wavelength signals and relatively high temperature operation makes quantum detectors unsuitable. Thermal detectors are also appropriate in applications requiring flat spectral response over a broad wavelength range. Specifically, a major NASA application is the Europa Jupiter System Mission (EJSM) that will provide a better understanding as to how gas giant planets and their satellites form and evolve. The Jupiter Europa Orbiter (JEO) is the NASA element of the EJSM. The readout ASIC, when developed on Phase II and combined with JPL thermopiles, will meet the thermal instrument requirements of the JEO and future planetary science missions. More »