Abstract: A laser apparatus with non-collinearly phase-matched frequency mixing includes a nonlinear crystal generating an output laser beam from non-collinearly phase-matched frequency mixing of first and second input laser beams. The output laser beam is subject to walk-off in a walk-off plane. The second input laser beam is less powerful than the first input laser beam. The first input laser beam is directed to more closely align its Poynting vector to the output beam Poynting vector than in collinear phase matching. To achieve good spatial overlap in this phase matching scheme, the second input laser beam is elongated in the walk-off plane, such that the second input laser beam has a greater transverse size than the first input laser beam in the walk-off plane. This non-collinear phase matching scheme is capable of achieving an improved beam quality of the output beam, as compared to collinear phase matching with circular input beams.

Abstract: A method for intracavity frequency conversion includes end-pumping a solid-state gain medium in a laser resonator with a pump laser beam to generate an intracavity laser beam circulating in the laser resonator, and frequency-converting a portion of the intracavity laser beam in a nonlinear crystal, located in the laser resonator, to generate a frequency-converted laser beam. The method controls the output power and at least one output beam parameter of the frequency-converted laser beam by adjusting (a) the pump power and (b) a resonator loss imposed on the intracavity laser beam. Taking advantage of both the pump laser beam and the intracavity laser beam contributing to thermal lensing in the gain medium, this control scheme is capable of controlling the output power and the output beam parameter(s) independently of each other.