Graded-phase mirror resonator with a super-Gaussian output in a CW-CO2 laser

Two graded-phase mirror (GPM) resonators have been designed to produce super-Gaussian output beam profiles of order 4 and 6. An inverse propagation method was used to calculate the appropriate shape of the GPM´s. Previous experimental work with a pulsed TEA-CO₂ laser has already confirmed the high transverse mode discrimination offered by such custom resonators, as anticipated by a theoretical analysis of their diffractional properties. Here, we extend these results by presenting new experimental measurements with a CW-CO₂ laser. The main objective of this paper is to demonstrate the super-Gaussian beam shape produced by these custom resonators. This is assessed with numerical simulations involving the incoherent superposition of transverses modes. The experimental results obtained with the GPM resonators, including measurements of the propagation of the output beam profile, are compared to those of a conventional semiconfocal cavity, and show higher monomode power extraction