Above threshold estimation of alpha (Henry) parameter in stripe lasers using near- and far-field intensity measurements

Henry parameter, α_H, is a key wavelength and carrier density dependent parameter which is central in determining the dynamic behavior of semiconductor lasers. While it may be extracted from below threshold measurements, its characteristics are of great interest above threshold where the lasers operate. We show that α_H along with the lateral gain profile may be determined above threshold in stripe laser structures through recovery of the lateral near-field phase profile. The lateral phase profile of the wave-front at the facet is calculated using measured near- and far-field intensities of the laser based on a model under scalar Helmholtz equation formulation. It is shown that α_H attains its maximum value under or in the proximity of the center of the pumped stripe. We apply the method to AlGaAs (λ = 776 nm) lasers with stripe widths ranging from 6-50 μm and with two levels of lateral current spreading achieved by having two different p-side cladding layer thicknesses. This permits comprehensive interpretation and analysis of the measured near- and far-field characteristics.