Longitudinally excited CO2 laser with short laser pulse and high quality beam

Abstract

We developed a longitudinally excited CO 2 laser with a tail-free short pulse and a high quality beam. The laser system had a longitudinal discharge tube, a long optical cavity and a simple driver circuit. The discharge tube was made of an alumina ceramic pipe with an inner diameter of 16 mm and a length of 45 cm, two metallic electrodes and two windows. Gas medium was a 20:1 mixture of CO 2 /N 2 at a pressure of 2.6 kPa. The optical cavity with the length of 180 cm was formed by an output coupler with a reflectivity of 70p and a high-reflection mirror. The optical cavity had an aperture or did not. The driver circuit consisted of −600 V pulse power supply and a primary capacitance of 9.6 μF, a step-up transformer, a storage capacitance of 700 pF, a spark gap and the discharge tube. The CO 2 laser produced a tail-free short pulse with the width of 281 ns. The CO 2 laser beam was a ununifomly distributed circular beam with the M 2 factor of 22.8 in the laser system without an aperture, a top-hat shape of circular beam with the M 2 factor of 9.61 in the laser system with a φ11-mm aperture, 5.40 in the laser system with a φ9-mm aperture, or a Gaussian shape of circular beam with the M 2 factor of 3.01 in the laser system with a φ7-mm aperture.