Analysis of the effects of feedback asymmetry in external cavity He-Ne lasers

A theoretical analysis of the characteristics of an external cavity He-Ne laser with asymmetric feedback induced by the misalignment of an external feedback mirror is proposed. The theoretical model considers both the multiple reflections and the phase variation caused by the asymmetric external cavity. It is found that the phase variation is of importance in determining the effects of asymmetric feedback. The three-order asymmetric feedback effects are experimentally observed and can be interpreted well by this model. The fringe frequency of the asymmetric optical feedback system can also be increased. The experimental results are in good agreement with the theoretical analysis. The theoretical and experimental results offer a potential increase in the resolution of an optical feedback system with asymmetric feedback. (c) 2006 Optical Society of America.