Optical Feedback Characteristics in He–Ne Dual Frequency Lasers

Abstract

Optical feedback characteristics in He–Ne dual frequency lasers arestudied systematically in different feedback power ratios with avariable attenuator. Feedback power ratios vary from 0.010 up to 0.998.Five distinct regimes of self-interference effects are found and definedas regimes I, II, III, IV and V. Accordingly, five opticalfeedback levels have been put forward in He–Ne dual frequency lasers.Strong mode competitions are observed in regimes III and IV.In regime V, multiple feedback effects are investigated. The basictheoretical analysis is also presented. Our results can advance theresearch of self-mixing interferometer and displacement sensor of He–Neorthogonally polarized dual frequency lasers.