High-frequency intensity modulation in orthogonal polarized dual frequency lasers with optical feedback

High-frequency modulation of laser output intensity is studied with asymmetric feedback induced by the misalignment of an external feedback reflector in an orthogonal polarized dual frequency laser. The fringe frequency of the optical feedback system is seven times higher than that of a conventional optical feedback system, due to multiple feedback effects. The output characteristics of two orthogonal polarized modes are also investigated. Mode competition is observed between the two modes. When initial intensities of the two modes are unequal, the mode competition will be strong. The difference in initial intensity between the two orthogonally polarized modes plays an important role in the mode competition with optical feedback. Experimental results are presented, as well as a theoretical explanation. The high-frequency modulation of laser intensity can greatly increase the resolution of an optical feedback sensing system.