Single frequency stabilized laser

Claim 1

In a frequency stabilized laser system of the type including a first assembly for rapidly compensating the laser resonant cavity length by small amounts to counteract factors tending to change said length and therefore the frequency of the emitted radiation of the laser, wherein said first assembly is rapidly acting and precise but has a relatively small dynamic adjustment range, the improvement comprising: a second assembly for at least approximately compensating said reasonant cavity length over a substantially larger adjustment range than the range of said first assembly, said second assembly comprising a spacer block supporting one resonant cavity-defining mirror from one end of the housing of the laser, said spacer block being of a material having a substantially different coefficient of thermal expansion than the material of said housing; said second assembly further comprising means for supplying thermal energy to said spacer block to change its length and therefore the position of said one mirror; and control means operatively connected to said second assembly to cause said second assembly to compensate said resonant cavity length over said relatively larger range to a length at least within said relatively small adjustment range of said first assembly, said control means comprising thermal energy adjusting means for controlling the effective thermal energy supplied to said spacer block; so that said laser system is frequency stabilized even when the large magnitude of the length-changing factors would otherwise have caused cavity length changes outside the relatively small dynamic adjustment range of said first assembly; said spacer block being of an effective length and of a material having a coefficient of thermal expansion of such value that the product thereof roughly compensates for the net potential change in length of the resonant cavity caused by thermal expansion of the material of the laser housing and other elements determining the effective spacing of said one mirror and the other resonant cavity defining mirror, but said length and coefficient of thermal expansion of said block being of such relative values that their product causes a slight mismatching in a known sense of the roughly compensated thermal expansion of said laser housing and other elements, whereby in the absence of any thermal energy supplied to said spacer block the effective spacing between said one mirror and said other resonant cavity defining mirror changes in a particular direction as the laser gradually warms up, so that an always positive amount of thermal energy is required to be supplied to said spacer block to compensate said thermal expansion of said laser housing and other elements to within the adJustment range of said first assembly.