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Polarization of eigenmodes in laser diode waveguides on semipolar and nonpolar GaN
J. Raß1, T. Wernicke2, W.G. Scheibenzuber3, U.T. Schwarz3, J. Kupec4, B. Witzigmann5, P. Vogt1, S. Einfeldt2, M. Weyers2, and M. Kneissl1,2
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
3 Department of Physics, Regensburg University, 93040 Regensburg, Germany
4 Integrated Systems Laboratory, ETH Zurich, Gloriastr. 35, 8092 Zurich, Switzerland
5 Computational Electronics and Photonics Group, University of Kassel, Wilhelmshöher Allee 71, 34121 Kassel, Germany
Published in:
phys. stat. sol. (RRL), vol. 4, no. 1, pp. 1-3 (2010).
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Abstract:
Recent calculations of the eigenmodes in waveguides grown
on semipolar GaN suggest that the optical polarization of the
emitted light as well as the optical gain depends on the orientation
of the resonator. Our measurements on separate confinement
heterostructures on semipolar (11 2) and (10 2)
GaN show that for laser resonators along the semipolar [11  ]
and [011] directions (i.e. the projection of the c-axis onto the
plane of growth) the threshold for amplified spontaneous
emission is lower than for the nonpolar direction and that the
stimulated emission is linearly polarized as TE mode. For the
waveguide structures along the nonpolar [100] or [110] direction
on the other hand, birefringence and anisotropy of the
optical gain in the plane of growth leads not only to a higher
threshold but alsoto a rotation of the optical polarization
which is not any more TE- or TM-polarized but influenced by
the ordinary and extraordinary refractive index of the material.
We observe stimulated emission into a mode which is
linearly polarized in extraordinarydirection nearly parallel to
the c-axis.
PACS::
42.25.Ja, 42.55.Px, 42.60.Lh, 78.20.Fm, 78.55.Cr, 78.67.De
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