Optical Techniques for the Fabrication of Laser Rods and Mirrors

Abstract

In our development of puled solid state lasers, optical techniques have been developed to fabricate laser rods and laser mirrors. Using the precision grinding and polishing techniques, the crystal is made into a cylindrical rod and the end faces arc ground and polished to a flatness of A/10 of sodium light and parallel to 2 to 5 seconds of an arc, using different grades of diamond paste and mild steel and wooden tools. The flatness of the rod is tested in an interferoscope and the parallelism between the two surfaces is measured with the help of an autocollimating system. To sustain laser action, a resonator cavity is essential. This is achieved by coating the end faces of the laser rod with alternate layers of suitable dielectric materials. External mirrors coated in the same way serve the same purpose. An optical monitoring system with a chopper and narrow band amplifier has been designed and fabricated to control the thickness of the dielectric coatings such that the desired reflectivities are obtained. Using these optical techniques, ruby and Nd, Glass rods and the necessary laser mirrors have been made and they are tested to give laser output.