Abstract: An electromagnetic wave ring resonator is disclosed including means to spatially rotate the electromagnetic field distribution of waves resonant therein about the direction of propagation of such waves to enable such waves to resonate with opposite senses of circular polarization, and means, including a laser amplifier medium, to provide different indices of refraction to resonant waves of the same sense of circular polarization as they pass through such laser amplifier medium in different directions. With such arrangement the two mentioned means enable the waves to resonate with four different frequencies. In a laser gyroscope using such ring resonator the electromagnetic field distribution rotating means includes a catoptric arrangement which, together with the last-mentioned means, reduces the loss, scatter and linear birefringence associated with the ring resonator included in such gyroscope.

Abstract: A four frequency laser gyroscope system having a rugged and compact output structure for producing output signals representing the frequency differences between counter-circulating wave pairs circulating as two beams within the gyroscope cavity. A partially transmitting dielectric mirror forms both one of the cavity reflectors and the means for extracting a small portion of each beam. The two extracted beams are combined on a beam splitter. Both the transmitted and reflected beams from the output of the beam splitter, each containing waves of all four frequencies, are utilized. Each resultant beam is then polarization discriminated to extract the desired signal content. The entire structure is adapted for rigid mechanical coupling and may be constructed to have a small size.