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7 February 2012 Multi-mode to single-mode switching caused by self-heating in bottom-emitting intra-cavity contacted 960 nm VCSELs
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Detailed investigation of anomalous modal behavior in fabricated bottom-emitting intra-cavity contacted 960 nm range vertical cavity surface emitting lasers (VCSELs) have been performed. At low currents the broad-aperture VCSELs show multi-mode operation at 945 nm via whispering gallery-like modes. Subsequent increase of pump current results in rapid increase of fundamental mode intensity and switching to a pure single transverse mode lasing regime at 960 nm with the higher slope efficiency. As a result record single transverse mode output power of 15 mW with a side-mode-suppressionratio (SMSR) above 30 dB was achieved. The observed phenomena cannot be explained by oxide-index guiding or changes in current pumping. 2D heat transport simulations show a strong temperature gradient inside the microcavity due to an effective lateral heat-sinking. This creates an effective waveguide and results in lower optical losses for the fundamental mode. At fixed pump current in pulsed regime (pulse width < 400 ns) high-order modes dominate, however the subsequent increase of pulse width leads to a rapid rise of optical power for the fundamental mode and SMSR increasing. Thus the self-heating phenomena play a crucial role in observed VCSEL unusual modal behavior.
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Sergey A. Blokhin, Nikolai A. Maleev, Alexander G. Kuzmenkov, James A. Lott, Marina M. Kulagina, Yurii M. Zadiranov, Andrey G. Gladyshev, Alexey M. Nadtochiy, Ekaterina V. Nikitina, Vladimir G. Tikhomirov, Nikolai N. Ledentsov, and Viktor M. Ustinov "Multi-mode to single-mode switching caused by self-heating in bottom-emitting intra-cavity contacted 960 nm VCSELs", Proc. SPIE 8276, Vertical-Cavity Surface-Emitting Lasers XVI, 82760W (7 February 2012);

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