Generating a geometric mode for clarifying differences between an operator method and SU(2) wave representation

Abstract

We study both numerically and experimentally a specific geometric mode, named VW mode, in an end-pumped Nd:YVO4 laser with a plano-concave cavity near the 1/3-degeneracy. Three theoretical methods are used to analyze the transverse profiles, the operator method [J. Opt. Soc. Am. A 22, 1559 (2005)], the SU(2) wave representation [Phys. Rev. A 69, 053807 (2004)], and the Fox-Li approach. Some differences among them are addressed and clarified. Moreover, the generating conditions for VW mode are found peculiar and its propagation character is demonstrated. By comparing the experimental mode patterns with the three numerical results, we conclude that the field of a geometric mode in the operator method should be extended to include those of the reverse directional trajectories and the SU(2) coherent state representation is found too specific to produce the fringes within some transverse patterns.