1D Confocal Broad Area Semiconductor Lasers (Confocal BALs) for Fundamental Transverse Mode Selection (TMS#0)

  • Previously in this journal we have reported on fundamental transversemode selection (TMS#0) of broad area semiconductor lasers (BALs) with integrated twice-retracted 4f set-up and film-waveguide lens as the Fourier-transform element. Now we choose and report on a simpler approach for BAL-TMS#0, i.e., the use of a stable confocal longitudinal BAL resonator of length L with a transverse constriction.The absolute value of the radius R of curvature of both mirror-facets convex in one dimension (1D) is R = L = 2f with focal length f.The round trip length 2L = 4f againmakes up for a Fourier-optical 4f set-up and the constriction resulting in a resonator-internal beam waist stands for a Fourier-optical low-pass spatial frequency filter. Good TMS#0 is achieved, as long as the constriction is tight enough, but filamentation is not completely suppressed. 1. Introduction Broad area (semiconductor diode) lasers (BALs) are intended to emit high optical output powers (where “high” is relative and depending on the material system). As compared to conventional narrow stripe lasers, the higher power is distributed over a larger transverse cross-section, thus avoiding catastrophic optical mirror damage (COMD). Typical BALs have emitter widths of around 100 ????m. Thedrawback is the distribution of the high output power over a large number of transverse modes (in cases without countermeasures) limiting the portion of the light power in the fundamental transverse mode (mode #0), which ought to be maximized for the sake of good light focusability. Thus techniques have to be used to support, prefer, or select the fundamental transverse mode (transverse mode selection TMS#0) by suppression of higher order modes already upon build-up of the laser oscillation. In many cases reported in the literature, either a BAL facet, the

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Author:Henning FouckhardtORCiD, Ann-Kathrin Kleinschmidt, Johannes Strassner, Christoph DöringORCiD
URN (permanent link):urn:nbn:de:hbz:386-kluedo-57342
Publisher:Hindawi Verlag
Document Type:Article
Language of publication:English
Publication Date:2019/06/17
Year of Publication:2019
Publishing Institute:Technische Universität Kaiserslautern
Date of the Publication (Server):2019/09/09
Number of page:6
Faculties / Organisational entities:Fachbereich Physik
DDC-Cassification:5 Naturwissenschaften und Mathematik / 530 Physik
Licence (German):Zweitveröffentlichung