Experimental test of a prototype gravitational radiation detector employing an active cavity laser sensor

A prototype gravitational radiation detector which uses two small He-Ne lasers in a heterodyne arrangement for displacement sensing has been built and tested. Operation of the system at the theoretical noise limit determined by spontaneous emission has been achieved. Above 2 kHz, the noise has a flat spectrum and is equivalent to displacements of 3*10-15 cm Hz-12/. It is shown that small active-cavity systems can be competitive with long-baseline Michelson interferometers when the high-quality mirrors and high-gain amplifying media are used.