The square-wave response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon.
© 2006 Optical Society of America
Lasers and Laser Optics
Original Manuscript: March 6, 2006
Revised Manuscript: April 18, 2006
Manuscript Accepted: April 20, 2006
Athanasios Gavrielides, Thomas Erneux, David W. Sukow, Guinevere Burner, Taylor McLachlan, John Miller, and Jake Amonette, "Square-wave self-modulation in diode lasers with polarization-rotated optical feedback," Opt. Lett. 31, 2006-2008 (2006)