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8 W high-efficiency high-brightness tapered diode lasers at 976 nm

: Kelemen, M.T.; Weber, J.; Kaufel, G.; Moritz, R.; Mikulla, M.; Weimann, G.


Zediker, M.S. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
High-power diode laser technology and applications IV : 23-25 January 2006, San Jose, California
Bellingham/Wash.: SPIE, 2006 (SPIE Proceedings Series 6104)
ISBN: 0-8194-6146-6
ISBN: 978-0-8194-6146-9
Paper 61040D
Conference "High-Power Diode Laser Technology and Applications" <2006, San Jose/Calif.>
Conference Paper
Fraunhofer IAF ()

Today tapered diode lasers are mainly used in external resonator configuration for non-linear spectroscopy or frequency doubling for blue-green outputs. Now increased output power and brightness make tapered lasers even attractive for pumping of fibre amplifiers or lasers and fibre coupled modules. We have realized high-power ridge-waveguide tapered diode lasers emitting at 976 nm. The high material quality of the MBE-grown laser structures yields a high internal efficiency of more than 97% and low internal losses of 0.5 cm-1. Tapered single emitters consist of a ridge section with a length of 500 ?m and a taper section with a length of 3000 ?m. The taper angle was 6°. A threshold current of 1.07 A corresponding to a threshold current density of 222 A/cm2 has been obtained. The maximum slope efficiency of 1.09 W/A together with the low series resistance of 35 m ohm results in a high wall-plug efficiency of 58% at 5.5 W output power. This high wall-plug efficiency remains nearly constant up to operation currents of 9 A corresponding to output powers of more than 8 W. At an operation current of 15 A an output power of 12.5 W has been achieved, which is to our knowledge the highest output power in continuous wave mode for tapered diode lasers reported so far. At 8 W a nearly diffraction limited behavior with values for M2 of less than 1.5 have been observed resulting in a brightness of more than 660 MW/cm2.