Patent ID: 7161967

Claim:
A method for checking the regulation state, with respect to a desired laser frequency V 0 , of a frequency-stabilized laser, comprising: providing a laser, tunable within a given tuning range; generating a laser beam at a frequency V L using said laser; modulating said laser beam at at least one first sideband frequency V RF ; modulating said laser beam at a second sideband frequency V FG at a known separation, which is defined by a frequency generator, from said desired laser frequency V 0 ; passing the laser beam, modulated at said at least one first sideband frequency V RF and at said second sideband frequency V FG , through an absorption material which has two or more absorption lines in said tuning range of the laser, said absorption lines being at different intervals from one another, with the laser frequency V L ; measuring the absorption of the second sideband frequency V O +V FG in the absorption material at successive times; and in response to said measuring determining no absorption for the second sideband frequency, tuning the laser frequency V L until said measuring determines absorption both at the laser frequency V 0 and at the second sideband frequency V O +V FG .