MODE DISCRIMINATION APPARATUS In an optical system such as a ring laser gyroscope cavity, oscillations occur in many transverse modes. The desired modes are allowed to exist by suppressing undesired modes utilyzing a light stop apparatus. One light stop is made by treating a dielectric mirror with an electron beam causing a phase change to occur to the undesired reflected waves. An alternative light stop is made by depositing an absorptive material on a dielectric mirror for absorbing some of the energy of the undesired modes. Both light stop embodiments are adjustable with respect to a laser wave in a resonant cavity.
MODE DISCRIMINATION APPARATUS