Above threshold modeling of single-spatial-mode edge-emitting diode lasers A. P. Napartovich * , N. N. Elkin, A. G. Sukharev, V. N. Troshchieva, and D. V. Vysotsky Troitsk Institute for Innovation and Fusion Research, 142190 Troitsk, Moscow region, Russia M. Nesnidal, E. Stiers AlfaLight Inc. 1832 Wright Street, Madison, WI, USA 53704 L. J. Mawst, D. Botez University of Wisconsin-Madison, 1415 Engineering Dr., Madison, WI, USA 53706 ABSTRACT There is an increasing need for single-spatial-mode, edge-emitting semiconductor lasers with reliable cw output power of around 1 W for applications such as pumps for rare-earth-doped fiber amplifiers and free-space communications. The design of respective devices is still a challenging task for experimenters, and software can assist very much in doing analyses of potentially perspective designs. We have developed a 3D numerical code supplied with a user-friendly interface for active diode-laser structures, taking into account light diffraction and carrier diffusion. The Watt-Ampere characteristics are calculated by changing the drive current density in the equation for the carrier-number density. To evaluate a single-mode stability limit, a procedure is developed to calculate 3-5 higher order optical modes on a ‘frozen background’: gain, carrier-induced index variation, as produced by the operated mode at a fixed drive level. Modal gains of these modes are compared to the calculated threshold gains for each mode. Because of non-uniform gain saturation by the operated mode, modal gains for higher-order modes increase with drive current due to beneficial overlap of their fields with the gain. When one of the higher-order modes approaches its threshold, this puts an upper limit for stable single-mode operation. A graphical interface allows for viewing near- and far-field patterns of any mode in the form of 3D surfaces or contour-plots. Scanning of profiles of mode intensity in an arbitrary cross section in the output plane and in far-field zone is available, too. Results of analyses of a number of published designs are reported. Keywords: diode laser, mode competition, gain spatial hole burning, interface 1. INTRODUCTION There is an increasing need for single-spatial-mode, 0.98-μm-emitting semiconductor lasers with reliable cw output power in excess of 1 W for applications such as pumps for rare-earth-doped fiber amplifiers (in fiber-optical communications) and free-space communications. Conventional positive-index-guided devices are limited by thermally induced kinks to stable, single-mode operation up to 800mW-1W cw range. However, such devices have small apertures: 4-5 μm. In turn that limits the reliability of fully facet-passivated devices (due to bulk degradation) to around 700 mW. Large - aperture (8–10μm) single-mode devices are required for significantly increased reliability, as well as for achieving reliable operation at powers in excess of 1 W cw. However, conventional devices suffer from the appearance of additional lasing modes that causes degradation in optical beam quality. The mechanisms responsible for mode competition are well known: gain spatial hole burning (GSHB) and self-focusing/defocusing associated with carrier- and thermally induced index variations. Both these factors, the GSHB and thermal lens, are to be taken into account in order to predict accurately single-mode operation limits. In this paper, study is made on effects associated with the GSHB and carrier-induced index suppression. Incorporation of thermal effects in the model is in progress, and will be reported later. Thus, our program package includes an optical subroutine with carrier distribution simulations in the framework of the diffusion equation and competing modes simulations on a “frozen” background. Effectiveness of this software is illustrated on two examples: an antiresonant reflecting optical waveguide (ARROW) diode laser [1, 2, 3] with apertures * E-mail: apn@triniti.ru Invited Paper Physics and Simulation of Optoelectronic Devices XIII, edited by Marek Osinski, Fritz Henneberger, Hiroshi Amano, Proc. of SPIE Vol. 5722 (SPIE, Bellingham, WA, 2005) 0277-786X/05/$15 · doi: 10.1117/12.589551 267