Abstract: An arrangement for the resonant frequency doubling of multimode laser radiation with resonators is provided, including mirrors and an optically nonlinear material. The arrangement ensures a dispersion-free tuning of the length of a passive resonator, and enables the frequency doubling of a multimode laser, which is resonant simultaneously for all modes of the laser radiation, and which is achieved by pairs of mutually oppositely disposed movable elements of an optically transparent material, such as prisms (P1, P2). The prisms are brought into the beam path of the resonator (R), formed from mirrors (M1 to M4) and optically nonlinear material (BBO). The prisms are movable elements (P1, P2) which are connected to adjusting elements such as piezoactuators, so that the optical length of the resonator (R) can be tuned and compensation for dispersion attained.

Abstract: A method for the production of Gaussian intensity distribution in the beam profile of secondary radiation generated by non-linear optical processes, particularly frequency conversion and more particularly frequency doubling of a primary radiation beam. The non-linearly generated, secondary radiation beam is non-Gaussian in profile due to the walk-off effect and has a near field path near the non-linear optical material and a transition field path interconnecting the near field path with a remote, or far, field path. A Gaussian secondary beam profile of substantially circular cross-section is produced at a finite distance from the optical material by providing an optical system in the transition path which, taken as a whole, has no divergence altering or imaging effect on the secondary radiation beam.

Abstract: A frequency-converted laser apparatus includes an optical pumping source that produces fundamental laser radiation and an external resonant cavity having one beam path direction-marked frequency conversion crystal within said resonant cavity or just beam path direction-marked frequency conversion crystals without an additional resonant cavity. The “to-be-used” direction of said frequency conversion crystal is well defined or clearly marked. The frequency converted laser radiation after said frequency conversion crystal shows better beam quality and much higher power stability if said frequency conversion crystal is used in the “to-be-used” direction.

Abstract: The invention relates to a method and device for frequency conversion, particularly for frequency doubling and particularly of continuous fixed frequency laser radiation, of semi-monolithic design with a ring resonator consisting of a mirror and an optically non-linear crystal. The objective of the invention is to develop a generic method and a device by means of which the frequency conversion, particularly the generation of the second harmonic from continuous fixed frequency laser radiation under avoidance of the disadvantages described, with high efficiency, with markedly enhanced opto-mechanical stability and a much simplified ease of production is assured, and is met by application of an electrical voltage to an annular piezo-adjuster 103 arranged between the mirror 101 and the crystal 102.