Spontaneous phase locking in a broad-area semiconductor laser

TL;DR

This paper reveals spontaneous phase locking of transverse modes in broad-area semiconductor lasers, showing complex, partially synchronized states similar to chimera states, driven by nonlinear dynamics and observed through high-resolution spectral analysis.

Contribution

It demonstrates the spontaneous formation of phase-locked mode multiplets in broad-area lasers, a phenomenon not previously observed, and links these states to chimera-like dynamics in laser systems.

Findings

Multiplets of phase-locked transverse modes are spontaneously created.

Phase locking occurs between modes of different transverse orders.

Some locked modes are generated by nonlinear dynamics, not passive cavity modes.

Abstract

Broad-area semiconductor lasers are employed in many high-power applications, however, their spatio-temporal dynamics is complex and intrinsically unstable due to the interaction of several transverse lasing modes. A dynamical and spatio-spectral analysis with ultra-high resolution of commercial broad-area lasers reveals multiplets of phase-locked first- and second-order transverse modes that are spontaneously created by the nonlinear dynamics for a wide range of operation parameters. Phase locking between modes of different transverse order is demonstrated by comparing the linewidths of the lasing modes to that of their beat note and by a direct measurement of their phase fluctuation correlations. The spontaneous phase locking is unexpected since the overall dynamics is unstable and the system lacks any intentional feature to induce locking. This partially synchronized dynamical state with groups of synchronized and unsynchronized laser modes coexisting is similar to what is called a chimera state in networks of coupled oscillators, hence indicating that such states may exist in a wider range of systems than previously assumed. Moreover, some of the phase-locked modes do not exist on the passive-cavity level, but are created by the nonlinear dynamics, an effect not previously observed in the context of partially synchronized laser modes.