Bessel–Gauss resonator with internal amplitude filter

We investigate a conventional resonator configuration, using only spherical curvature optical elements, for the generation of Bessel–Gauss beams. This is achieved through the deployment of a suitable amplitude filter at a Fourier plane create by careful selection of the geometric cavity parameters, such as mirror curvatures and resonator length. We analyze the loss behaviour of the odd and even modes, and show that the lowest Bessel–Gauss mode does not necessarily have the lowest loss.