Abstract: A source of narrow-band coherent radiation has a first optical parametric oscillator (OPO 1) for producing seed radiation, and a second optical parametric oscillator (OPO 2), into which the seed radiation is input after passing through a wavelength-selective element (G). In order to stabilize and adjust the bandwidth of the radiation (14) emitted by the second optical parametric oscillator (OPO 2), radiation of this type is also input into the wavelength-selective element (G) and thereby analyzed, in order, in accordance with the analysis, to adjust the wavelength-selective element or the OPO 2.

Abstract: A laser arrangement for generating narrow-band, tunable coherent radiation has an optical parametric oscillator (10) and a tunable seed oscillator (20) whose emitted seed radiation can be set in a narrow-band fashion by means of at least one wavelength-selective element (30). In order to achieve simple tunability of the output radiation (38) of the OPO in conjunction with a narrow bandwidth, good spatial beam quality and high beam intensity without maladjustment of the OPO resonator, the lineshape, set using the wavelength-selective element (30), of the seed radiation I.sub.seed (.lambda.), and the intensity transmission function T.sub.opo, (.lambda.) of the non-pumped resonator (12, 14) of the OPO (10) are set in such a way that given tuning of the center wavelength .lambda..sub.max seed of the seed oscillator (20) in the middle between two neighboring transmission maxima of the intensity transmission function T.sub.opo (.lambda.) it holds for all wavelengths .lambda. not equal to .lambda..sub.

Abstract: A tunable narrowband source of a coherent radiation, comprisinga first optical parametric oscillator (OPO1) which includes at least one first optical parametric amplifier medium (K.sub.1) in a resonator (18, 20; 20, 34) or an optical parametric generator;at least one second optical parametric oscillator (OPO2) which includes at least one second optical parametric amplifier medium (K.sub.