Isotropic nonplanar ring laser

Abstract

A nonplanar ring laser for use as a laser gyro includes an even number of at least six reflecting surfaces which are preferably all made from the same coating batch or coating run so that they have substantially the same anisotropy characteristics. The mirrors are divided into pairs of mirrors, and the mirrors in at least each pair must match in their anisotropic characteristics. Note that the matched mirrors need only be in the laser path but not necessarily adjacent. The nonplanar geometric arrangement of the reflecting surfaces is such that the reflecting plane of incidence of each mirror is at substantially a right angle to the reflecting plane of incidence of at least one of the adjacent mirrors in the laser path. Note that the reflecting plane of incidence of each mirror may optionally be at right angles to the reflecting planes of incidence of both its adjacent mirrors in the laser path. The angles of incidence of the mirrors in each matched pair must be substantially the same. Using this geometry, and at least the mirrors in each matched pair being from a single coating batch having the same anisotropy characteristics, the phase and attenuation shifts which are introduced by imperfect coatings are cancelled in the ring laser cavity. Due to the substantial reduction in phase and attenuation anistropy this ring laser configuration reduces coupling between the two modes travelling in the same direction when used in a multioscillator laser gyro, and therefore improves gyro performance.