Time-resolved spatial profile of TEA CO_2 laser pulses: influence of the gas mixture and intracavity apertures

Abstract

The evolution of the intensity profile of transversely excited atmospheric CO_2 laser pulses is investigated within the intensity moment formalism. The beam quality factor M_2 is used to study the mode evolution. Attention is focused on the influence of both the gas mixture (N_2:CO_2:He) and the diameter of an intracavity diaphragm placed to attenuate higher-order modes. The degree of accuracy that can be attained by approximating the laser field amplitude by means of the lower-order terms of a Hermite-Gauss expansion is also analyzed. In particular, a bound for the truncation error is given in terms of two time-resolved spatial parameters, namely the beam width and the M_2 parameter.