Frequency-Doubled, Single-Frequency Neodymium YAG Laser.

The report deals with the theoretical and experimental work done on the basic techniques and successful operation of a stable, frequency-doubled, single-frequency NdYAG laser. An efficient, resonant cavity design with the Nd YAG rod acting as an internal focusing element was used to attain adequate TEM sub 00 mode volumes in the laser rod and the small beam waists at the nonlinear crystal Ba2NaNb5O15 necessary for optimum intracavity second-harmonic generation. Various mode filters were investigated, resulting in the use of a double, intracavity Fabry-Perot etalon arrangement to obtain single-frequency operation of the NdYAGlaser with relative ease. Mode competition effects were studied, and the necessary conditions for stable single-frequency operation at both 1.06 and 0.53 micrometers were established. Techniques and component designs were successfully developed to obtain all the frequency-doubled output in a single direction. These included appropriate cavity geometries and the design of doubly reflecting laser mirrors for both 1.06 and 0.53 micrometers including phase considerations, and also the development of AR coatings on Ba2NaNb5O15 effective at both wavelengths. The adequacy of the techniques adopted was demonstrated, and a unidirectional, single-frequency, frequency-doubled power output of 0.35 W obtained consistently from a 5 by 50 mm NdYAG rod pumped by a tungsten-iodine lamp operated at approx 850 W in a spherical pump cavity.