Laser clamping assembly and method

Details Laser clamping assembly and method Laser clamping assembly and method

1999-04-21

2002-05-07

Davie, James W. (Department: 2874)

Coherent light generators

Particular temperature control

C036S066000, C036S06700D

Reexamination Certificate

active

06385220

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the field of solid state lasers and more particularly to a clamping arrangement and method for a solid state laser media that mitigates thermal focusing and depolarization of laser radiation stimulated within the medium of the solid state laser.
BACKGROUND OF THE INVENTION
In general, the problem with laser systems is to achieve power that is as high as possible, and also to maintain stable laser performance over a broad power range (i.e. from low to high power). Laser power dependent thermal lensing or temperature induced changes in the index of refraction of the laser material that cause distortion of the laser beam as it passes through the laser material have been a major impediment to achieving stable laser operation over a broad power range. Typically, solid state lasers are designed to operate at a single operating power so that constant pumping power and constant temperatures are maintained thereby stabilizing thermally-induced effects to the laser material. However, many current lasing applications require that a user controlled variable output power feature be available in order to enhance the functionality of the laser.
Disc or thin plate lasers have been proposed in the prior art to at least partially deal with this problem (See for example U.S. Pat. No. 5,553,088 issued Sept. 3, 1996, hereby incorporated by reference).
The advantage of disc or thin plate laser systems is that the solid body can be pumped at a high pumping power since the heat resulting thereby can be transferred to a solid cooling element via a cooling surface at one or both ends.
The temperature gradient formed in the solid body does not lead to a negative effect on the beam quality of the laser radiation field at high pumping power since the laser radiation field propagates approximately parallel to the temperature gradient in the solid body so the laser radiation field “sees” the same temperature gradient in all the cross-sectional areas. In summary, the use of an end-cooled disc or thin plate laser material geometry can in principle result in reduced thermal lens distortion.
However, in practice, non-amplified solid state laser assemblies (including disc, slab, and rod type laser mediums) continue to be hampered by thermal effects when pumped at broad power ranges (i.e. from low to high power).
SUMMARY OF THE INVENTION
An object of the present invention is to provide a laser clamping assembly and method for a laser material within a solid state laser that has reduced thermo-mechanical distortion of the laser material and consequently reduced distortion of an output laser beam.
Another object of the present invention is to provide a laser clamping assembly and method for a laser material within a solid state laser that generates a high quality diffraction-limited beam.
Another object of the present invention is to provide a laser clamp assembly and method for a laser material within a solid state laser that has reduced optical and polarization distortion.
Another object of the present invention is to provide a laser clamping assembly and method for a laser material within a solid state laser that is less susceptible to material fractures and mechanical distortion due to stress from large thermal gradients caused by increased pumping power.
Another object of the present invention is to provide a laser clamping assembly and method for a laser material within a solid state laser that reduces the effects of pumped-induced heating of the laser material on the properties of the laser output beam.
In accordance with one aspect of the present invention there is provided a laser clamping system for a laser medium in a solid state laser comprising: (a) a first member made from a heat conductive material; (b) a second member constructed to allow a laser beam to pass therethrough substantially unattenuated, the laser medium being disposed between and in contact with the first and second member; and (c) means for applying pressure to the laser medium through the first and second members to inhibit thermo-deformation of the laser medium.
In accordance with another aspect of the present invention there is provided a laser clamping system for a laser medium in a solid state laser comprising: (a) two heat conducting members, each heat conducting member having a generally planar surface, the two heat conducting members being oriented to receive the laser medium such that the laser medium contacts the generally planar surfaces of the two heat conducting members; (b) at least one of the heat conducting members allows the laser beam to pass therethrough substantially unattenuated and unchanged; and (c) pressure means for holding both heat conducting members in contact against the laser medium, whereby the heat conducting members and the pressure means remove heat from the laser medium under pumping conditions.
In accordance with another aspect of the present invention there is provided a thin-plate laser comprising: (a) a solid state laser medium configured as a thin-plate; (b) two heat conductive members capturing the solid state laser medium therebetween, the two heat conductive members each generally conforming to one of a pair of opposed surfaces of the solid state laser medium to facilitate heat transfer from the solid state laser medium to the two heat conductive members; (c) at least one of the heat conductive members being optically transparent to transmit pumping light from a source to the solid state laser medium; and (d) force applying means for applying pressure to the heat conductive members to restrain the solid state laser medium from mechanical deformation under pumping conditions.
In accordance with another aspect of the present invention there is provided a method for enhancing an output of a laser having a solid state laser medium, the method comprising the steps of: (a) pumping the solid state laser medium through at least one of two heat conductive members, one heat conductive member being disposed in thermal contact with each of two generally opposed surfaces of the solid state laser medium; (b) removing heat from the solid state laser medium via the two heat conductive members; and (c) applying pressure to the heat conductive members to restrain the solid state laser medium from mechanically deforming under pumping conditions to mitigate thermal focusing and depolarization of laser radiation stimulated with the solid state laser medium.


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