Improving Diode Pumped Alkali Laser (DPAL) Beam Quality by Inducing Refractive Index Gradients

We have recently predicted that large radial gradients of the refractive index induced by the pump beam in the heated gain medium of diode pumped alkali lasers (DPALs) could lead to improved DPAL beam quality. This effect depends on the composition of the buffer gas in the cell. We verified this counterintuitive finding by careful measurements of the beam quality factor M2 in static Cs DPALs with different compositions of the buffer gases. Computations of M2 in Cs DPALs with different He/hydrocarbon ratios using wave optics model coupled to gas dynamics code and comparison of the calculated and experimental results were also performed. The results of the present study were published in R. Luzon, et. al, Improving the beam quality of DPALs by refractive index gradients induced by the pump beam in the heated gain medium: experimental verification of the theoretical prediction", J. Opt. Soc. Am. B 38, 550-552 (2021). It is suggested that further work on the modeling of multi-mode diode pumped lasers interaction with hydrocarbons should be carried out, aiming at getting better agreement with the experimental results.