INFLUENCE OF EXTERNAL OPTICAL FEEDBACK ON POLARIZATION SWITCHING IN INGAASP INP LASERS/

Optical feedback effects on the emission properties of 1.3 mu m InGaAs P/InP ridge waveguide lasers were studied experimentally for both de p umping and current modulation. The laser diodes used in our experiment s showed a current-induced transition from TM to TE polarization witho ut external feedback. At external optical feedback, the current for th e onset of TM/TE transition droped by 25 mA and multiple TM/TE switchi ng was observed over a large current interval. The dynamic response of the external-cavity laser to current pulses of various width was foun d to depend sensitively on the fine tuning of the external cavity leng th, resulting in TM/TE oscillations of 2 or 10 GHz, respectively, in t he case of 2 ns current pulses. The physical mechanism responsible for the observed behaviour is discussed.