Power-scalable optical system for nonlinear frequency conversion

A system for frequency-conversion of a pump radiation, the system comprising:

• i) a laser source generating the pump radiation;
• ii) a nonlinear optical element for frequency-conversion of the pump radiation, said nonlinear optical element including a nonlinear birefringent crystal shaped as a thin plate, said thin plate having a thickness and having a front-surface and a back-surface with a size in all directions being larger than said thickness, said nonlinear optical element generating at least one frequency-converted beam as compared to a frequency of the pump radiation, and all involved beams propagating fulfilling phase matching or quasi-phase matching conditions in said nonlinear optical element;
• iii) said nonlinear optical element including a partial reflective coating at said front-surface and a high-reflective coating at said back-surface of said nonlinear crystal yielding to resonant intensity enhancement of the laser pump radiation and at least one of the frequency-converted beams, said high-reflective coating being configured to reflect all involved wavelengths and to conserve or adjust a relative phase delay between the at least one frequency-converted beam and the pump radiation upon an internal reflection for maintaining the relative phase delays between various beams yielding optimal frequency-conversion;
• iv) a heat sink in thermal contact with said nonlinear optical element, said heat sink having a controllable temperature enabling efficient cooling of said nonlinear crystal and generating a temperature gradient in said nonlinear crystal substantially orthogonal to said back-surface and approximatively in a direction of propagation of laser beams, and reducing a temperature inhomogeneity in said nonlinear crystal, for decreasing phase matching inhomogeneity between the various beams.