Passive Feedback Control in a Ruby Laser

摘要

This research investigates the feasibility of pulse stretching in a Q-switched ruby laser by means of passive feedback control. Control of pulses with half widths of less than 300 nanoseconds is of special interest as this cannot be accomplished with presently existing active feedback systems due to the delay time involved. Intuitively it is felt that inserting a loss into the laser cavity that increases with laser power would limit the peak spike power. If the spike energy remains constant an increase in spike width will result. Two such loss systems are reported here. One is a loss due to the frequency discrimination of the laser linewidth. Laser power is shifted in frequency by stimulated Rayleigh wing scattering to higher loss sections of the linewidth. The amount of shift and the amount of power shifted are power dependent. The second system involves discrimination on the basis of polarization. The induced rotation of the polarization ellipse associated with self-focusing is used. The Rayleigh effect produces control at lower power levels than the induced polarization rotation system. (Author)