Development of a dielectric corona pre-ionized TEA CO2 laser with CO2-rich gas mixture suitable for second harmonic generation

Abstract

A simple dielectric corona pre-ionized TEA CO2 laser, which is suitable for SHG applications, has been developed with the help of high concentration of carbon dioxide. The intense, very uniform UV pre-ionization and low-inductance discharge circuit permit the best laser performance with a gas mixture rich in CO2. In order to achieve the most acceptable combination of the peak power, output energy and pulse duration, not only N2:CO2 ratio varies in favor of CO2 but also helium concentration is significantly reduced. When CO2 concentration varied from 20 to 53% in the experiment, a more symmetrical, shorter output pulse (a FWHM of ∼60 ns) with a significantly lower tail and a lower energy (∼700 mJ) was obtained with a rich gas mixture of CO2:N2:He = 10:1:8 than a lean gas mixture of 1:1:3 while the peak output power was virtually kept constant (∼5.8 MW). The effect of the laser gas mixture on optimizing the energy and time parameters of SH waveform has been studied numerically. The calculations show that for the rich gas mixture the residual tail of the SH pulse is completely eliminated by the nonlinear conversion and the corresponding waveform has a lower total duration (∼600 ns). Moreover, the energy conversion efficiency can be increased by 29% with the rich mixture compared to the lean mixture.