Suppression of Cavity Time-Delay Signature Using Noise-Phase-Modulated Feedback

We propose reconfiguration of the conventional feedback scheme to suppress the external-cavity time-delay signature (TDS) by adding noise phase modulation in the feedback of semiconductor laser. Noise-phase-modulated feedback introduces broad band noise frequencies into the feedback light and enables the suppression of the TDS. In this work, by means of simulations, the effect on TDS suppression of phase modulation (PM) index is explored. In addition, the influence of noise bandwidth variation is investigated. Using the auto-correlation function to quantity the TDS, we find that, for a large range of operating parameters, the TDS is significantly suppressed to the noise level and even submerged into the base noise. It is shown that suppression TDS is achievable over a wide operating parameter provided the noise generator bandwidth is of order 10 GHz and the PM index is greater than about 3. The proposed configuration will have widespread applications in contexts where suppression of the TDS is required.