Laser system and method using plural gain elements and thermal lensing

Claim 1

A laser system comprising: first and second solid state active gain elements, the second active gain element having an input face and output face; at least one common optical pump operable to excite said first and second active gain elements, the excitation being such as to induce thermal lensing power at least in the second active gain element; a laser resonator comprising at least an output coupler, wherein the first active gain element is located within the resonator and provides an output beam from the output coupler; and at least one optical coupler operable to couple and steer the output beam from the output coupler into the input face of the second active gain element, wherein the output beam from the output coupler is a divergent beam having a wavefront with a radius of curvature that increases with propagation distance in the region of the second active gain element; the system being configured such that the wavefront radius of curvature at the input face of the second active gain element is matched to the thermal lensing power of the second active gain element so that a substantially collimated beam emerges from the output face of the second active gain element.

Claim 9

A method for obtaining a substantially collimated output beam from a laser system comprising first and second solid state active gain elements, the second element having an input face and output face; at least one common optical pump operable to excite said first and second active gain elements, the excitation being such as to induce thermal lensing power at least in the second active gain element; a laser resonator comprising at least an output coupler, the first active gain element being located within the resonator and providing an output beam from the output coupler; and at least one optical coupler operable to couple and steer the output beam from the output coupler into the input face of the second active gain element, the method comprising obtaining an output beam from the output coupler which is divergent, having a wavefront with a radius of curvature that increases with propagation distance in the region of the second element, wherein the radius of curvature of the beam at the input face of the second element is selected or adjusted so that it matches the thermal lensing power of the second element so as to obtain a substantially collimated output beam from the second active gain element.

Claim 10

A method for obtaining a substantially collimated output beam from a laser system comprising first and second solid state active gain elements, the second element having an input face and output face; at least one common optical pump operable to excite said first and second active gain elements, the excitation being such as to induce thermal lensing power at least in the second active gain element; a laser resonator comprising at least an output coupler, the first active gain element being located within the resonator and providing an output beam from the output coupler; and at least one optical coupler operable to couple and steer the output beam from the output coupler into the input face of the second active gain element, the method comprising obtaining an output beam from the output coupler which is divergent, having a wavefront with a radius of curvature that increases with propagation distance in the region of the second element, wherein the radius of curvature of the beam at the input face of the second element is selected or adjusted so that it matches the thermal lensing power of the second element so as to obtain a substantially collimated output beam from the second active gain element.