Narrow-band interference filter and its application in a laser system

摘要

A narrow-band interference filter comprises a plurality of alternating reflective dielectric layer systems arranged in a serial sequence in layer form on a substrate. Each system has a construction pattern (HL). sup.2 H, and a pair of spacing layers LL is arranged between adjacent layer systems. An H layer has a high index of refraction, and an L layer has a low index of refraction, the H and L layers being of the same optical thickness. A plurality of absorbent metal layers are interposed into the layer arrangement to act asymmetrically in relation to the reflection of light passing through the layers, the metal layers having thicknesses which are less than the geometrical thicknesses of the layers H and L. The filter, because of the asymmetrical reflection characteristic has an infinitesimal reflection for light passing therethrough in one direction. For an interposed with an active laser medium within a resonator having a pair of reflectors the filter forms a subsidiary resonator with one of the reflectors.