Solid state laser apparatus with auxiliary intra-cavity mirror elements

Claim 1

In a laser apparatus including a solid state active laser element provided with a pair of optical end surfaces aligned along a central laser axis; an optical resonant cavity formed by a pair of main mirror elements spaced apart and optically aligned along said laser axis with said laser element disposed therebetween for defining a main laser beam path; and a pulsed excitation source for pumping said laser element at sufficiently high repetition rate to produce thermal focussing effects in said laser element that normally cause some of the light energy emanating from said element and reflected from said mirror elements to stray off said main laser beam path; the improvement comprising: a pair of auxiliary apertured mirror elements mounted within said optical resonant cavity one on each side of said active laser element; said auxiliary apertured mirror elements each provided with a single aperture aligned with said laser axis and in registry with the optical end surfaces of said active laser element; said apertures being congruent with and spaced close to said optical end surfaces; said auxiliary apertured mirror elements having surfaces facing said main mirror elements that are substantially totally optically reflecting for intercepting said stray light energy and reflect it back towards said main mirror elements and into said main laser beam path.