This award supports the study of the response spectrum of the Avalanche Breakdown (AB) detector, and its high detection sensitivity in the far infrared. Recently, response has been measured for very low powers at a wavelength of 151 microns. This approaches the ultimate quantum detectivity limit. The detector element is n-type germanium maintained unconventionally at a bias current above the point of impact ionization. Under these conditions, the signal current is found to be proportional to the square rood of the incident power. Although several mechanisms have been suggested to explain this unusual behavior, none has yet proven satisfactory. The Free Electron Laser (FEL) at University of California, Santa Barbara, will be used to measure the detector's response spectrum over a wide range in the far infrared. These studies will provide the theoretical framework necessary for further work as well as more complete experimental results.
