Patent ID: 7068689

Claim:
A method for producing laser radiation comprising the steps of: (a) providing an optical pumping source for producing optical pumping radiation; (b) arranging a Brewster-cut frequency conversion crystal in a first configuration for frequency conversion, wherein a beam of the optical pumping source passes through the crystal in a first direction, and the normal of a first entrance surface of the Brewster-cut frequency conversion crystal forms a Brewster angle with the beam of the optical pumping source, and measuring a first output power of the converted radiation; (c) arranging the Brewster-cut frequency conversion crystal in a second configuration, for frequency conversion, wherein the beam passes through the crystal in a second direction, the second direction being the reversed direction of the first beam path direction, the second configuration being obtained by rotating the crystal by 180 degrees with respect to the first arrangement about an axis perpendicular to the horizontal cross section of the crystal, the normal of a second entrance surface of the Brewster-cut frequency conversion crystal forming a Brewster angle with the beam of the optical pumping source, and measuring a second output power of the converted radiation; (d) determining a preferred beam path direction of a frequency conversion crystal by determining the configuration of the first and second configurations which results in a higher output power of the converted radiation over time; and (e) amplifying radiation of an optical pumping source by using an optical cavity having at least one frequency conversion crystal disposed such that said crystal is passed by the radiation only in the predetermined preferred beam path direction.