Index antiguiding in narrow ridge-waveguide (In,Al)GaN-based laser diodes
J. Appl. Phys., vol. 114, no. 113102 (2013).
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The threshold current density of narrow (1.5 µm) ridge waveguide (In,Al)GaN based laser diodes is found to strongly depend on the ridge etch depth. By solving the complex-value two-dimensional waveguide equation, it is shown that, for shallow-ridge devices with a small built-in index step, the dependence of the modal gain on the material gain is strongly influenced by antiguiding effects. Taking into account the lateral extension of the material gain beyond the ridge as well as the optical mode absorption in the unpumped regions of the quantum wells, the observed differences in the threshold current density can be reproduced by simulations.
1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
2 Institute for Solid State Physics, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany