8 May 2008 Oblong-shaped VCSELs with pre-defined mode patterns
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We report on the theoretical analysis and fabrication of a novel type of vertical-cavity surface-emitting laser (VCSEL) that provides selection of a certain higher-order transverse mode. This selection is based on a spatial variation of the threshold gain by adding an antiphase layer with an etched relief structure. The field intensity profile emitted from this laser is calculated numerically as well as with an analytical approach. The main factors that control the selected mode such as the threshold gain, the confinement factor, and the phase parameter are calculated as a function of the active aperture, aiming to achieve single higher-order transverse mode emission. For a given aspect ratio of a rectangular oxide aperture, the threshold gain difference between the selected and neighboring modes is maximized via the relief diameter and the size of the aperture. The fabrication process involves selective etching of the antiphase layer, passivation of the relief, oxidation of an AlAs layer to the desired aperture after reaching this layer using wet-chemical etching. N- and p-metalization processes are applied, followed by polyimide passivation. Finally, bondpad metalization is carried out for electrical contacting. Mode selection is successfully achieved. Attractive applications for such devices are found in optical manipulation of micro-particles such as sorting and separation.
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Abdel-Sattar Gadallah, Andrea Kroner, Ihab Kardosh, Fernando Rinaldi, Rainer Michalzik, "Oblong-shaped VCSELs with pre-defined mode patterns", Proc. SPIE 6997, Semiconductor Lasers and Laser Dynamics III, 69971R (8 May 2008); doi: 10.1117/12.781099; https://doi.org/10.1117/12.781099

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