A system, method and apparatus for operating a laser at a downhole location is disclosed. A gas is configured to receive an output of a laser and to absorb a selected wavelength of the laser corresponding to a selected spectral line of the gas. A pressure device reduces broadening of the selected spectral line related to a temperature at the downhole location. A photodetector receives light from the gas chamber and provides a measurement related to the received light. A processor alters an operating parameter of the laser using the obtained measurement to operate the laser.