Laser-induced Damage in Diamond

Abstract

AN observation of laser-induced damage in clear diamond has recently been reported¹ and the conclusions there drawn are that damage occurred on the exit face only and that small holes cannot be drilled because of damage by acoustic phonons. This is contrary to our experience. Using a ruby laser operating in relaxation oscillations with an output of only 0.2 joule and a beam divergence of 3 milliradians, we can produce a hole with two laser shots. Fig. 1 shows such a hole of 40µ diameter through a diamond plate 0-5 mm thick cut parallel to the (110) plane. The laser beam was focused on to the front (110) surface by a plano-convex lens of 17 mm focal length, creating a triangular depression in this surface. Blackening of the walls of the hole also occurred, probably due to graphitization. This diamond plate had also been hit by the same laser operating with a rotating prism Q-switch to give a 5 MW pulse, beam divergence 1 milliradian, focused by an 8-mm microscope objective. Under these conditions blackening and damage occurred on the exit surface only and can be seen on the right of Fig. 1. The microscope objective was wrecked in the process.