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Near-field evolution in strongly pumped broad area diode lasers

: Hempel, M.; Tomm, J.W.; Baeumler, M.; Konstanzer, H.; Mukherjee, J.; Elsässer, T.


Belyanin, A.A. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Novel in-plane semiconductor lasers XI : 23 - 26 January 2012, San Francisco, California, United States; part of SPIE Photonic West
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8277)
ISBN: 978-0-8194-8920-3
Paper 82771H
Conference "Novel In-Plane Semiconductor Lasers" <11, 2012, San Francisco/Calif.>
Fraunhofer IAF ()
high power broad area diode lasers; near-field; filamentation; degradation; catastrophic optical damage

Many applications such as pumping of solid state lasers or ignition of explosives require high optical output powers during a short period. Pulsed operated diode lasers meet these requirements. They can be driven at elevated power levels, well above the ones specified for continuous wave (cw) operation. The optical near-field intensity of a diode laser in this operation regime is a key parameter since it determines the beam properties of the device. High power AlGaAs/GaAs quantum well broad area diode lasers are subjected to single pulse step tests carried out up to and beyond their ultimate limits of operation. Laser near-fields are monitored on a picosecond time scale using a streak-camera setup during pulse currents of up to ~50 times the threshold current. A transition from gain guiding to thermally-induced index guiding of the near-field is shown. Further power increase is prevented by catastrophic optical damage (COD). This sudden failure mechanism is studied in conjunction with filamentary properties of the near-field. The defect growth dynamics resolved on the picosecond time scale is used to gather inside into the physics behind COD.