A laser resonator including a gain medium with strong thermal-lensing properties includes an arrangement for providing near real-time compensation for variations in the thermal-lensing effects in the gain-medium resulting from variations in resonator operating parameters.
CROSS REFERENCE TO PRIOR APPLICATIONS
This application is a Continuation-in-Part of application Ser. No. 08/924,176, filed Sep. 5, 1997 and now U.S. Pat. No. 5,912,912, issued Jun. 15, 1999.
The present invention relates to a stable solid-state Raman laser, the solid-state Raman laser including a resonator cavity defined by at least two reflectors, a laser material located in the resonator cavity and capable of generating a cavity laser beam which propagates within the resonator cavity, a solid Raman medium located in the resonator cavity for shifting the frequency of the cavity laser beam to produce a Raman laser beam which propagates within the resonator cavity; and an output coupler for coupling and outputting the Raman laser beam from the resonator cavity, wherein at least one parameter selected from the group consisting of the position of the laser material relative to the position of the Raman medium in the cavity, the length of the cavity and the curvature of at least one of the reflectors, is selected such that changes in the focal lengths of both the laser material and the Raman medium as a result of thermal effects in the laser material and the Raman medium during operation of the laser do not substantially cause instability in the power of the output Raman laser beam. A method of maintaining stable operation of a solid state Raman laser is also described.
A mode-synchronized solid-state laser comprising a laser medium inside a laser resonator which is formed by a resonator mirror and an output coupling mirror and which is folded by at least one concave folding mirror, with a saturable absorber inside the laser resonator and with at least one laser pump source whose pump beam pumps the laser medium, wherein the elongated resonator length L is a function of the pulse repetition frequency and the latter is determined by a distance between the resonator mirror and the output coupling mirror. An elliptic beam profile inside of the laser resonator which is caused by an inclination of an optical axis of the at least one concave folding mirror relative to a folded optical axis of the laser resonator is eliminated by an elliptic thermal lens in the laser medium whose optical action generates an ellipticity of the beam profile which is offset by 90.degree. relative to the elliptic beam profile generated by the folding mirror, wherein, by virtue of the material characteristics, the crystallographic orientation and the geometric dimensioning of the laser medium and by a choice of intensity and intensity distribution of the pump beam in the laser medium, the degree of ellipticity of the thermal lens is adjusted in such a way that the most uniform possible energy density distribution occurs over the irradiated zone of the saturable absorber.
Disclosed is a diode-pumped solid-state laser having an asymmetrical optical resonator provided with at least two resonator mirrors, inside said resonator being provided at least one thermal lens having an optical refractive power D and having two principal planes respectively and said resonator being definable by the following stability criteria: 0<G.sub.1G.sub.2<1 with G.sub.1=1-L*/R.sub.1-Dd.sub.2 G.sub.2=1-L*/R.sub.2Dd.sub.1 and L*=d.sub.1+d.sub.2-Dd.sub.1d.sub.2 d.sub.1,d.sub.2 the distances of the resonator mirror from the principal planes of the thermal lens R.sub.1, R.sub.2 the radii of curvature of the resonator mirrors. The invention is distinguished by the values d.sub.1,d.sub.2,R.sub.1 and R.sub.2 being selected in such a manner that the following critical refractive powers D.sub.I,D.sub.II,D.sub.III and D.sub.IV, for which ##EQU00001## ##EQU00001.2## applies, the following equations are fulfilled: D.sub.II-D.sub.I=D.sub.IV-D.sub.III.gtoreq.8 dptr. |D.sub.III-D.sub.II|.gtoreq.2 dptr.
In a diode-pumped laser amplifier the inventive object is to increase the tolerance of the amplifier arrangement relative to variations of the input parameters significantly, so that fine-tuning is no longer necessary for guaranteeing the stability of the amplifier. Into a laser-active solid-state medium where a thermal lens of a strength which is different in orthogonal planes is generated in consequence of the irradiated pump radiation, a laser beam to be amplified is directed into the laser-active solid-state medium while being focused in the plane with a strong thermal lens, wherein a beam waist that is being generated lies in the area of the thermal lens. The laser amplifier can be used for amplifying the radiation of an oscillator.
An optical pulse-shaper includes a prism, a delay line having positive optical power and a reflective spatial light modulator. In one arrangement the delay line has a selectively variable optical path length for accommodating pulses of different spectral bandwidth and positive optical power is provided by a concave mirror. In another arrangement, the delay line includes a zoom-mirror arranged to provide selectively variable optical power for accommodating pulses of different spectral bandwidth.
