Adjustable responsivity for thermal infrared detectors

With the recent interest in adaptive IR imaging, focal plane arrays are desired that can operate linearly over an enormous dynamic range. Unfortunately, large signals can cause thermal detectors to operate at temperatures significantly above their ambient resulting in intensity dependent performance or even device damage. In this letter, the responsivity of microbolometer devices is controlled using the detector and substrate as a simple electrostatic actuator. Microbolometers are demonstrated to switch between states that are over a factor of 50 apart in responsivity. The limits of the switching are theoretically separated by four to five orders of magnitude. In addition, intermediate values of responsivity can be obtained by designing devices in which the support beams snap down at lower voltage than the detector plate. Combining this idea with the pressure dependence of the thermal contact conductance, continuous thermal conductance tuning over a factor of 3 is demonstrated. (C) 2002 American Institute of Physics.