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High-brightness laser diodes using angular filtering by total reflection

Laserdioden mit hoher Brillanz durch Winkelselektion mit Hilfe von Totalreflektion
: Rogg, J.; Boucke, K.; Kelemen, M.T.; Rinner, F.; Pletschen, W.; Kiefer, R.; Walther, M.; Mikulla, M.; Poprawe, R.; Weimann, G.


Mawst, L.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
In-plane semiconductor lasers V : 22 - 23 January 2001, San Jose, USA
Bellingham/Wash.: SPIE, 2001 (SPIE Proceedings Series 4287)
ISBN: 0-8194-3965-7
Conferene on In-Plane Semiconductor Lasers <5, 2001, San Jose/Calif.>
Fraunhofer IAF ()
high brightness; hohe Brillanz; high-power diode laser; Hochleistungs-Diodenlaser; Z-Laser; InGaAs/AlGaAs; semiconductor laser diode; Halbleiterlaserdiode

A high power semiconductor laser with a novel lateral design using angular filtering by total reflection for increased brightness is demonstrated. In this so called "Z-Laser" two inner surfaces guide the laser beam by total reflection in a Z shaped path through the laser. Higher order laser modes with larger divergence angles are suppressed because of a smaller reflectivity. This results in a reduced far-field angle. Simulations based on a two-dimensional steady state wave equation solved by using the Pade approximation, an one-dimensional carrier diffusion equation and a logarithmic gain model have been performed to design the device. First prototypes of the laser were fabricated on MBE grown InGaAs/AlGaAs wafers. The inner surfaces providing the refractive index step necessary for total reflection were prepared by chemically assisted ion-beam etching. Single lasers were mounted junction side down on copper heat-sinks. They show lateral far field angles smaller than 2 deg FWHM in excellent agreement with numerical simulations. Output powers of more than 500 mW cw out of a 36 µm facet have been reached. In conclusion, the "Z-Laser" is a promising new design for high power, high brightness semiconductor laser diodes.