Submillimeter Photon Counting In Ruby (Correspondence)

A microwave detection process very similar to Bloembergen´s quantum counting has been observed in the vicinity of 500 Gc using the fluorescence of ion pairs in red ruby. The detector which has been realized is quite sensitive and particularly simple because it uses polychrornatic light for pumping. The results reported here are preliminary, and the apparatus is not refined for detection beyond the stage at which feasibility has been shown.