Experimental Study of Time-Delay Signatures in Vertical-Cavity Surface-Emitting Lasers Subject to Double-Cavity Polarization-Rotated Optical Feedback

Suppression of time-delay (TD) signature in a vertical-cavity surface-emitting laser subject to double-cavity polarization-rotated optical feedback has been verified experimentally. The TD signature, represented by the autocorrelation coefficient at the delay time in the external cavity, is measured in the two orthogonal polarizations of the laser. The results show that TD signatures with double-cavity feedback can be 22% to 35% weaker than those with single cavity feedback for the same experimental parameters. For appropriate feedback polarization, TD signatures become invisible. This is in good agreement with the theoretical prediction. Our results also show that higher feedback strength results in greater suppression in TD signatures in a wide range of polarization angle.