TECHNIQUES FOR SUPER-MODE OSCILLATION.

By means of a frequency selective coupler, more than 50 percent of the multimode power of a He-Ne laser was obtained at a single frequency. The amplitude stability of this single-frequency output was strongly dependent on the behavior of the power stabilization system used to control the positions of the laser mirrors. 28 mw of single-frequency light was obtained from a 50 mw He-Ne laser using the stabilization system described in the previous report. One of the limitations on the use of the super-mode technique is the very high peak-phase deviation ratio T that results from the operation of high-power FM lasers. Recently we have been able to operate an FM He-Ne laser with an internal phase perturbation driven at twice the axial mode interval of the laser cavity. The result of this 2c2L excitation is an FM laser with approximately half the usual number of driven modes and thus half the modulation index to be un-modulated by the super-mode modulator. The preliminary design for the control system to absolutely stabilize the frequency of the FM laser has been completed.