INFLUENCE OF CARRIER SPREADING ON THE CURRENT-CONTROLLED LATERAL-MODE BEHAVIOR OF TWIN-STRIPE LASERS

Near- and far-field patterns, lasing efficiency, and spectra of twin-stripe lasers as a function of the injected current ratio were systematically examined with particular interest in their dependence on the carrier spreading which was controlled by the interstripe etched depth. As for lasers lightly etched not deeper than 0.5 μm to the active layer, the near-field peak shifts with current ratio at a higher rate for deeper etching, which leads to the more drastic change of the lasing efficiency. At the same time, the peak direction of the far-field pattern and the peak wavelength also changes at a higher rate for deeper etching. The dependence of these characteristics on the etching depth can be attributed to the higher current isolation for deeper etching. These results mean that laser beam deflection and nonlinear light-current characteristics, which are particularly important for information processing, can be controlled by the interstripe etched depth. As for lasers deeply etched down to 0.3 μm to the active layer, the regions below the stripes lases independently from each other which are ascribed to both the strong isolation of carriers and the considerable dip in the built-in index in the interstripe region.