Second-order acceleration for optical power measurement using axial thermopile detectors

Abstract

A method of accelerating the response of thermopile detectors is proposed for optical power measurements. The physical model of the detectors is established, and the theoretical response is derived. The response is not completely described by a single exponential function. The difference between the conventional latency compensation method assuming a single exponential leads to overshoot and deviation from the equilibrium state. A new method with second-order differential operations is proposed, which is more appropriate for the non-exponential responses. In simulations, the second-order method theoretically shows 67% improvement in the measuring time. Experiments based on fabricated copper-substrate detectors show 43%, 65%, and 56% reduction in the measurement time compared with the conventional method, under the deviation ranges of ± 1%, ±0.5%, and ± 0.3%, respectively. Since the method is based on the adiabatic mechanism that generally exists in the light absorbing process, it is compatible with various types of calorimetric detectors.