Effects of nonlinear frequency pulling on the cavity phasing and the collective mode structure in phase-locked VCSEL arrays

Carrier and gain depletion due to cross-cavity interactions in actively coupled vertical-cavity surface-emitting laser arrays cause nonlinear-cavity frequency pulling. As a result the collective mode structure departs significantly from earlier studied linearly coupled eigenmodes. Theory and simulations find that array eigenmodes have uniform amplitude and density distribution over the interior array sites, accompanied with boundary-layer formation at the edges. Exact zero or pi phasing among adjacent sites is achieved, depending on the coupling-strength sign. In contrast, in linearly coupled array modes neglecting cross-cavity hole burning, the phase difference cannot be exactly zero or pi, yielding a sinusoidal amplitude distribution over the array sites. The exact zero phasing and the uniform intensity distribution in nonlinearly coupled arrays offer advantages for practical applications. (c) 2006 Optical Society of America.