All-solid-state single-frequency continuous wave laser

An all-solid-state single-frequency continuous wave laser, comprising a symmetric ring resonant cavity, a first gain crystal and a second gain crystal symmetrically arranged in the symmetric ring resonant cavity, and a gain unit symmetrically arranged between the first gain crystal and the second gain crystal;

• wherein the symmetric ring resonant cavity comprises an output cavity mirror and a first cavity mirror arranged symmetrically to the output cavity mirror, and a second cavity mirror at a front end of the first gain crystal, the output cavity mirror, the first cavity mirror and a third cavity mirror at a front end of the second gain crystal form a 8-shaped optical path;
• wherein the gain unit comprises at least one gain crystal arranged in sequence, and in the gain unit, a third gain crystal nearest to the first gain crystal and a fourth gain crystal nearest to the second gain crystal are symmetrically arranged;
• wherein each gain crystal is coupled with a separate pump source, an optical diode is arranged between the second cavity mirror and the output cavity mirror, and a nonlinear crystal is arranged at a beam waist between the first cavity mirror and the output cavity mirror;
• wherein two gain crystals symmetrically arranged are the same, and each gain crystal acts as a gain medium and a mode-matching element.