Abstract A method of stabilizing the operating frequency of a laser which includes comparing by means of interference the relative phase of two beams of radiant energy from the laser, one of which is a reference while the other passes through the active lasing material. The optical path traversed by the reference beam is adjusted to produce a selected condition at the point of interference when the laser is oscillating at a frequency which corresponds exactly to an anomaly in the dispersion of the lasing material. Thereafter, the laser frequency is stabilized by adjusting its operating frequency to maintain this condition. Preferably, the comparison is made by varying the reference phase about the selected value. Apparatus for performing this method includes means defining two substantially equal optical paths for radiation emitted by the laser, one of which extends through the active material of the laser. The two paths are terminated at the same point so that interference occurs and the apparatus includes means for detecting the output from the point of interference. Finally, means are provided for controlling the laser frequency to maintain a predetermined interference condition.
A method of stabilizing the emission frequency of a laser including a resonant cavity and an active material which comprises the steps of: providing a first path for a first beam of radiation emitted by said laser, said path having an optical length which includes a controllable variation; providing a second path for a second beam of radiation emitted by said laser and passing through said active material; setting said laser to emit at a frequency corresponding to an anomaly in the dispersion of said active material; adjusting the optical length of said first path to produce a predetermined phase difference between the respective beams when said emitted radiation is at said frequency; comparing the beam at the end of said second path with that at the end of said first path by permitting said beams to interfere; detecting the amplitude of radiation produced from said interference of said beams; and changing said optical length of said resonant cavity to reduce to zero any component in said detected radiation which is at the frequency of said cyclic variation of the optical length of the first path.
Claim 2
Independent Claim
186 words
A method of stabilizing the emission frequency of a laser including a resonant cavity and an active material which comprises the steps of: providing a first path for a first beam of radiation emitted by said laser, said path having an optical length which includes a controllable variation; providing a second path for a second beam of radiation emitted by said laser and passing through said active material; setting said laser to emit at a frequency corresponding to an anomaly in the dispersion of said active material; adjusting the optical length of said first path to produce a predetermined phase difference between the respective beams when said emitted radiation is at said frequency; comparing the beam at the end of said second path with that at the end of said first path by permitting said beams to interfere; detecting the amplitude of radiation produced from said interference of said beams; and changing said optical length of said resonant cavity to reduce to zero any component in said detected radiation which is at the frequency of said cyclic variation of the optical length of the first path.
Claim 3
Dependent Claim
27 words
The method of claim 1 in which the phase difference between the respective beams produced by adjusting the optical length of the first path is pi radians.