Since the invention of VECSELs, vast spectral coverage has been demonstrated with emission wavelengths in the range from the UV to almost the MIR. Accordingly, a great variety of different quantum well and quantum dot gain designs have been applied so far to achieve such versatility. A novel gain design for GaAs based VECSELs emitting at wavelengths >1.2 μm employs type-II quantum wells, which exhibit spatially indirect charge-carrier recombination. The first VECSEL based on such a design has been demonstrated very recently. Our device consists of ten (GaIn)As/Ga(AsSb)/(GaIn)As heterostructures arranged as a resonant periodic gain. We summarize the development of this pioneering structure and discuss the fundamental laser characteristics, such as carrier densities, gain temperatures and slope efficiency. Remarkable output powers up to 4 W are demonstrated in multi-transverse mode operation at 1.2 μm. Also, the performance in TEM00 operation is investigated, with an M2 < 1.13. One major difference to conventional type-I gain structures is a characteristic blue shift of the material gain. Due to the importance of the detuning in quantum well based surface-emitters, the blue shift has to be considered as a critical designing parameter. Hence, we carry out a detuning study in order to determine an optimal detuning. As an important part of the optimization, the experimental results are compared with fully microscopic simulations.
Christoph Möller, Christian Fuchs, Christian Berger, Fan Zhang, Arash Rahimi-Iman, Martin Koch, Antje Ruiz Perez, Stephan W. Koch, Jörg Hader, Jerome V. Moloney, and Wolfgang Stolz, "The development and fundamental analysis of type-II VECSELs at 1.2 μm (Conference Presentation)," Proc. SPIE 10087, Vertical External Cavity Surface Emitting Lasers (VECSELs) VII, 100870L (Presented at SPIE LASE: January 31, 2017; Published: 21 April 2017); https://doi.org/10.1117/12.2252882.5387835711001.
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