Power-law fluctuations near critical point in semiconductor lasers with delayed feedback

Abstract

Since the analogy between laser oscillation and second-order phase transition was indicated in the 1970s, dynamical fluctuations on lasing threshold inherent in critical phenomena have gained significant interest. Here, we numerically and experimentally demonstrate that a semiconductor laser subject to delayed optical feedback can exhibit unusual large intensity fluctuations characterized by power-law distributions. Such an intensity fluctuation consists of distinct intermittent bursts of light intensity, whose peak values attain tens of times the intensity of the maximum gain mode. This burst behavior emerges when a laser with a long time delay (over $100\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$) and an optimal feedback strength operates around the lasing threshold. The intensity and waiting time statistics follow power-law-like distributions. We also report on the experimental results that suggested power-law intensity dynamics in a semiconductor laser with delayed feedback. The reason for the emergence of power-law behavior in the laser system is discussed from the perspective of nonequilibrium-critical behavior in a slowly driven-dissipative system known as self-organized criticality.