Analysis of eigenfields in the axicon-based Bessel-Gauss resonator by the transfer-matrix method: comment

Numerical calculations recently published [J. Opt. Soc. Am. A23, 912 (2006)] on the eigenmodes in axicon-based Bessel-Gauss resonators revealed significant inconsistencies regarding the modal patterns, the mode losses, the mode ordering by loss, and the intracavity field distributions. We show that the results are inaccurate mainly because (a) it was overlooked in the derivation of the matrix equations that light crosses twice through the axicon in a complete round-trip and (b) the numerical method used to evaluate the diffraction integral equations cannot resolve the eigenvalues and eigenfields for the given resonator configuration.