Unstable laser apparatus

摘要

An unstable laser with improved beam quality has a laser medium and a pair of crossed Porro prism end reflectors positioned to form a resonator defining a light path through the laser medium. Beam expansion optics magnify the beam with each pass through the resonator and is accomplished with a negative lens at one end of the resonator and a telescope at the other end. The negative lens produces a diverging beam through a laser medium in one direction and the telescope recollimates the beam in the reverse direction. Radially varying birefringent compensation is accomplished in the resonator with a crystalline waveplate. Output coupling is achieved through the use of the waveplate in conjunction with polarizer optics.