Spatial structures in broad-area vertical-cavity regenerative amplifiers

Summary form only given.The spatial structure of broad-area semiconductor lasers and possibilities of its control are a subject of considerable interest both from a fundamental and an application point of view. In particular, recent work predicts the possibility of addressable soliton-like excitations (cavity solitons) in semiconductor microcavities. Their demonstration might enable new forms of all-optical information coding and processing with the speed, compactness and robustness of a semiconductor device. We study the spatial structure of broad-area semiconductor regenerative amplifiers using vertical-cavity surface-emitting lasers, which are biased electrically around threshold and subjected to external injection of a homogeneous beam. The investigated devices are bottom-emitters based on three InGaAs/GaAs quantum wells in a /spl lambda/-cavity emitting in the 970 to 990 nm region. The spatial length scale of the patterns did not depend significantly on the beam parameters of the injected beam as long as it is enlarged. Tight focusing however produced an excitation of a broad spectrum of transverse wavevectors. Contrary to expectation we did not observe a distinct threshold for the appearance of the off-axis wavevectors. This is attributed to the fact that a seeding of the instability is provided by spontaneous scattering at boundaries and/or irregularities or by the finite wavevector spectrum of the incident beam if it is focused.