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Investigations were conducted in the areas of second harmonic generation and mode locking with CW neodymium:YAG Lasers. Demonstration of consistent and reproducible 100% conversion of the available CW power at 1.06 microns into 0.53 micron power was accomplished at a level of 2.1 watts in the TEM(oo) mode. A completely electronic closed loop automatically stabilized mode-locking system was developed, with capability of tracking plus or minus 1.5% variations in cavity length. Experimental and theoretical investigations of combined mode locking and intracavity second harmonic generation using a common Ba2NaNb5O15 crystal showed that there was a strong interaction between the processes, the nonlinear harmonic generation having a serious effect on mode-locking effectiveness. Thermal effects due to absorption in the nonlinear crystal were shown to have a significant effect on second harmonic generation. Correlation between theory and experiment was obtained. (Author)

The results of an experimental program designed to produce the maximum, stable second harmonic power from a mode-locked Nd:YAG laser using external second harmonic generation are reported. The laser was operated C.W. at the 2 to 3 watt level in a TEM transverse mode, and mode locked at 500 MHz. The major results were: Up to 400 mw of second harmonic power with a conversion efficiency of 15% was generated and demonstrated to be stable (less than 10% drift) over testing periods of 15 minutes or greater. A maximum of 550 mw of second harmonic was generated at 16% efficiency but at this level the system was stable for only a few minutes.

Observations of the spatial non-uniformities of laser gain indicated that the origin of this effect is laser light trapped within the ruby rod. Experimental and theoretical work with laser amplifier systems resulted in the development of a 3000 MW amplifier system. Systems with output half-power pulsewidths in the 50 - 250 microsec range were also developed. The limits of achievable performance were investigated, with allowances made for technologically feasible improvements and differing amplifier and oscillator component configurations. Amplification of the output of a curvedmirror interferometer was shown to be the most practical approach for producing high-brightness and spikeless laser output. Y2O3:Eu(+3) crystals of 1/4-inch diameter and one-inch length were grown. Difficulties encountered in lasing suggest the use of Gd(+3) as an additive ion. (Author), See also AD-424 737.

Measurements to correlate the gain profile of ruby laser rods with optical quality and pumping light intensity. Curved mirror optical cavities were studied with regard to the production of spike free laser outputs. A feedback system with Pockels cell gain control was constructed and applied to a ruby laser. Development of a multi-gigawatt oscillator-amplifier system was completed. Y2O3:Eu(3+) was tested as a laser material with no success thus far. (Author)