Background fluctuation limit of infrared detection of thermal waves at high temperatures
Jochen Bolte, Ji H Gu, Bruno K Bein
Starting from the basic principles of photon detection, a general theoretical description is given for the incoherent background fluctuation limit of thermal wave detection. Different cases of infrared detection of thermal waves are considered: differential detection over a narrow detection interval, Δλ; integral detection over a larger wavelength interval; two background regions which are at different stationary temperatures and from which radiation is collected under different solid angles. The theoretical limits are compared with measurements obtained for different infrared detectors and different experimental conditions. Good agreement between the observed detection limits and theoretical prediction is obtained. The minimum thermal waves detected with the help of an indium arsenide detector vary between δT / mK approx. 30 at 350 K and δT / mK approx. 0.5 at 800 K; the minimum thermal wave amplitudes resolved with the help of a mercury cadmium telluride detector are δT / μK approx. 44 at 300 K, δT / μK approx. 15 at 400 K, and δT / μK approx. 9 at 500 K.