Cavity dumping of a laser in its unstable frequency regime

Claim 2

Optical apparatus comprising a laser including an optical resonator and an active medium disposed therein, means for pumping said medium to generate a beam of optical radiation, modulator means located within said resonator and approximately at the waist of said beam, signal forming means for applying a periodic train of extraction pulses to said modulator to cause output pulses of optical radiation to exit from said resonator, said laser having an unstable regime of operation wherein the amplitude and/or timing of said output pulses is random when the repetition rate of said extraction pulses is at or near the relaxation oscillation frequency of said laser, characterized in that said laser is operating in said regime, and said signal forming means includes means for applying to said modulator, after each extraction pulse is applied thereto, a holding pulse having an amplitude effective to keep said laser operating slightly above its threshold and having a duration so that after said holding pulse is removed, the internal power in said resonator is allowed to build up to approximately maximum before the next succeeding extraction pulse is applied to said resonator, so that said output pulses are stable in both amplitude and timing.

Claim 3

The apparatus of claim 1 wherein said modulator is an acousto-optic modulator.

Claim 4

The apparatus of claim 1 wherein said active medium comprises Nd:YAG.

Claim 5

The apparatus of claim 3 wherein said laser has a relaxation oscillation frequency of approximately 50 kHz and said unstable regime extends from about 30 kHz to about 125 kHz.

Claim 6

The apparatus of claim 1 including feedback means connected to said signal forming means and responsive to the internal power in said resonator for adjusting the slope of said holding pulse so that during said holding pulse the internal power in said resonator is maintained at a relatively low level as compared to the level of internal power which would exist in the absence of said feedback means.

Claim 7

The apparatus of claim 5 wherein said feedback means is effective to produce an increasing slope with increasing time of said holding pulse.

Claim 8

An optical device comprising: a laser including an active medium, a means for pumping said medium to generate a beam of electromagnetic radiation, an optical cavity resonator comprising at least first and second reflectors, said medium being located within said resonator and on an optic axis thereof, said cavity resonator having a geometry such that the beam of radiation has a waist in a region near the center of curvature of said second reflector, and modulator means located at approximately the center of curvature of said second reflector, signal forming means for applying a periodic train of extraction pulses to said modulator means to cause output pulses of optical radiation to exit from said resonator, said laser having an unstable regime of operation wherein the amplitude and/or timing of said output pulses is random when the repetition rate of said extraction pulses is at or near the relaxation oscillation frequency of said laser, characterized in that said laser is operating in said regime, and said signal forming means includes means for applying to said modulator means, after each extraction pulse is applied thereto, a holding pulse having an amplitude effective to keep said laser operating slightly above its threshold and having a duration so that, after said holding pulse is removed, the internal power in said resonator is allowed to build up to approximately maximum before the next succeeding extraction pulse is applied to said resonator, so that said output pulses are stable in both amplitude and timing.

Claim 9

An optical device comprising: a laser including an active medium, a means for pumping said medium to generate a beam of electromagnetic radiation, an optical cavity resonator comprising at least first and second reflectors, said medium being located within said resonator and on an optic axis thereof, said cavity resonator having a geometry such that the beam of radiation has a waist in a region near the center of curvature of said second reflector, and modulator means located at approximately the center of curvature of said second reflector, signal forming means for applying a periodic train of extraction pulses to said modulator means to cause output pulses of optical radiation to exit from said resonator, said laser having an unstable regime of operation wherein the amplitude and/or timing of said output pulses is random when the repetition rate of said extraction pulses is at or near the relaxation oscillation frequency of said laser, characterized in that said laser is operating in said regime, and said signal forming means includes means for applying to said modulator means, after each extraction pulse is applied thereto, a holding pulse having an amplitude effective to keep said laser operating slightly above its threshold and having a duration so that, after said holding pulse is removed, the internal power in said resonator is allowed to build up to approximately maximum before the next succeeding extraction pulse is applied to said resonator, so that said output pulses are stable in both amplitude and timing.