Over the last 25 years since their invention, CO2 lasers have slowly and steadily evolved as one of the most mature laser systems for various technological applications. It remains a predczninant source of radiation for applications in the strategic longer wavelength infrared atmospheric window range. The successful application of CO2 lasers will require optical canponents capable of operating at these laser waveiengths. A CO2 laser detector is an important component among these, and is the subject of this paper. In the earlier period after their invention, it was difficult to find suitable detectors for CO2 laser wavelengths. Available quantum detectors required cooling with liquid helium. Thermal detectors lacked the sensitivity and speed of photon detectors. However, the advantage of thermal detectors has been their room temperature operation.