Enhanced photoacoustic beam profiling of pulsed lasers

Abstract

An improved version of a photoacoustic beam profiler of pulsed lasers is presented. The new model resorts to high-bandwidth condenser microphones to register higher-order, excited acoustic modes, thus enabling more accurate profiling. In addition, Xe was used as a buffer gas since its high atomic weight further reduces the eigenfrequencies. Furthermore, a new gas-handling system makes up for some deficiencies found in the first model. The system was calibrated using the Airy pattern generated with a pinhole illuminated by a frequency-doubled Nd:YAG laser that excited NO 2 NO 2 traces. Once calibrated, the beam profile of a TEA CO 2 CO 2 laser was obtained, using ethylene as the absorbing species. This profiler returns more accurate profiles than thermal paper.