Single Photon Detection Using Optical Heterodyne Interferometry

We detail and explore the application of heterodyne interferometry for a weak field coherent detection scheme. Planned use in a current dark matter search experiment sets specification goals to accurately measure fields on the order of 1 photon per week. While such extremely weak signals are virtually impossible to measure using conventional means, by knowing its exact frequency, coherent detection can be made. Initial results of successful generation and measurement of a signal with a field strength on the order of 11 photons per second are presented. Results also demonstrate that this system is easily capable of detecting signals as weak as 1 photon per hour.