Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 31: GaN: Bauelemente
HL 31.2: Talk
Saturday, March 5, 2005, 15:15–15:30, TU P-N201
Mode dynamics in (Al,In)GaN laser diodes — •Markus Pindl1, Ulrich T. Schwarz1, Michael Furitsch2, Andreas Leber2, Alfred Lell2, and Volker Härle2 — 1Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany — 2OSRAM Opto Semiconductors GmbH, Wernerwerkstr. 2, 93049 Regensburg, Germany
Stable and well defined optical modes in laser diodes (LDs) are of major interesst in the design of (Al,In)GaN lasers. Impropper geometric properties of the waveguide can cause the appearance of higher lateral modes, unstable modes, mode filamentation, and beam-steering. A stable fundamental mode operation is essential for sophisticated applications like laser printers or optical data storage. We used a self-built scanning near-field microscope (SNOM) to investigate the mode behaviour of the LDs. To analyze the temporal dynamics, the SNOM has a time resolution of 5 ns. The SNOM measurements show the near-field of the optical mode directly on the facet of the LDs. To investigate effects like beam-steering, we also measured lateral cuts in the x/z plane directly in the middle of the propagating beam in a distance of 0 µ m − 20 µ m to the laser facet. We found that the LDs suffer form filamentation, mode hopping, and beam-steering if the ridge width of the waveguide is wider than 2 µ m. The cuts of the propagating beam in the x/z plane show a tilting and, in some cases, also a splitting of the beam. Because the cuts of the propagating beams show not only the near-field of the optical mode, but also how the mode propagates in the free space, one can find informations about the phase in the near-field of the LD.