Technique and apparatus for stabilizing the frequency of a gas laser

Claim 1

An apparatus for stabilizing the output of a laser at a desired frequency comprising an absorption cell in optical alignment with said laser output, means operably connected to said laser and to said absorption cell for passing said laser output twice through said absorption cell, said cell containing a gas and a pair of plates therein, an RF voltage source and an AF voltage source electrically connected together and to said plates for subjecting said gas to an RF field and an AF field in order to induce DC absorption sidelobes in said gas, said gas exhibiting a first order Stark effect, having an absorption line centered near the desired frequency for the laser output and having a pressure sufficiently low that (a) the absorption line of said gas is Doppler broadened and (b) the linewidth of said gas is substantially less than the RF frequency applied thereto, a phase sensitive detecting system operably connected to said AF voltage source and to the output emanating from said absorption cell after being twice passed therethrough, and means operably connecting said phase sensitive detecting system to said laser for varying said laser output in accordance with a signal from said phase sensitive detecting system whereby by applying said RF field at a frequency which is the difference between the desired operating frequency for the laser output and the frequency of the center of the absorption line of said gas said laser output can be locked to said desired frequency.

Claim 2

An apparatus for stabilizing the output of a laser at a desired frequency comprising an absorption cell in optical alignment with said laser output, means operably connected to said laser and to said absorption cell for passing said laser output twice through said absorption cell, said cell containing a gas and a pair of plates therein, an RF voltage source and an AF voltage source electrically connected together and to said plates for subjecting said gas to an RF field and an AF field in order to induce DC absorption sidelobes in said gas, said gas exhibiting a first order Stark effect, having an absorption line centered near the desired frequency for the laser output and having a pressure sufficiently low that (a) the absorption line of said gas is Doppler broadened and (b) the linewidth of said gas is substantially less than the RF frequency applied thereto, a phase sensitive detecting system operably connected to said AF voltage source and to the output emanating from said absorption cell after being twice passed therethrough, and means operably connecting said phase sensitive detecting system to said laser for varying said laser output in accordance with a signal from said phase sensitive detecting system whereby by applying said RF field at a frequency which is the difference between the desired operating frequency for the laser output and the frequency of the center of the absorption line of said gas said laser output can be locked to said desired frequency.

Claim 6

A method for stabilizing the output of a laser at a desired frequency comprising the steps of: a. twice passing the output of a laser through a gas which exhibits a first order Stark effect and has an absorption line centered near the desired frequency for said laser output and has a pressure sufficiently low that the absorption line of said gas is Doppler broadened and the linewidth is substantially less than an RF frequency applied thereto, b. applying said RF field and an AF field to said gAs in order to induce DC absorption sidelobes therein, said RF field being maintained at a frequency which is the difference between the desired operating frequency for the laser output and the frequency of the center of the absorption line of said gas, c. analyzing the output after having twice passed through said gas in order to determine whether an absorption of the laser output at the desired frequency has taken place, and d. utilizing said analysis in order to vary the laser output in accordance therewith thereby producing a laser output which is locked to said desired frequency.

Claim 7

A method for stabilizing the output of a laser at a desired frequency comprising the steps of: a. twice passing the output of a laser through a gas which exhibits a first order Stark effect and has an absorption line centered near the desired frequency for said laser output and has a pressure sufficiently low that the absorption line of said gas is Doppler broadened and the linewidth is substantially less than an RF frequency applied thereto, b. applying said RF field and an AF field to said gAs in order to induce DC absorption sidelobes therein, said RF field being maintained at a frequency which is the difference between the desired operating frequency for the laser output and the frequency of the center of the absorption line of said gas, c. analyzing the output after having twice passed through said gas in order to determine whether an absorption of the laser output at the desired frequency has taken place, and d. utilizing said analysis in order to vary the laser output in accordance therewith thereby producing a laser output which is locked to said desired frequency.