Single longitudinal mode frequency converted laser

A single longitudinal mode frequency-converted solid-state laser includes an optical pumping source that produces optical pumping radiation, a coupled resonant cavity having a first resonant cavity and a second resonant cavity sharing a common partially reflecting mirror, a solid-state laser medium disposed within the first resonant cavity and pumped by the optical pumping radiation, and an optical wavelength converting means within said second resonant cavity. The laser medium generates a first laser radiation at a first wavelength which is converted by the wavelength converting means into a second laser radiation at a second wavelength. A temperature controlling means controls the temperatures of the first and the second resonant cavities and of the optical pumping source. The optical path lengths of the first resonant cavity and the second resonant cavity are selected such that only one longitudinal mode of the coupled resonant cavity is within the gain bandwidth of the laser medium. Thus, the single longitudinal mode can oscillate in said coupled resonant cavity. The laser has fewer intracavity elements and thus fewer internal optical losses and a higher efficiency.