Nonlinear Optics in AlGaAs (1990s)

The Optoelectronics Research Group at the University of Glasgow were world leaders in the recognition, understanding and application development of nonlinear guided waves in the AlGaAs alloy semiconductor. It was recognised that ultrafast nonlinear refraction (denoted by n2 or the real part of χ(3), and also referred to as the optical Kerr effect) is enhanced in the spectral region just below the half-bandgap, and, more importantly, it avoids the detrimental effects of two-photon absorption. For the optical communications wavelength of 1550nm, this corresponds to an Al alloy fraction of 0.18 to 0.20. The refractive index change is only present when the optical field is present and therefore the speed of the effect is determined the shortness of the optical pulse, usually limited by dispersion.

Experimental demonstrations included all-optical switching in directional couplers, Mach-Zehnder interferometers, temporal and spatial solitons.

The figure shows the deduced orientational dependence of nonlinear refraction for linear and circular polarised light based on experimental observations.

Polarisation and crystallographic orientational dependence of nonlinear refraction in AlGaAs

Some of the key concepts of The Nonlinear Optical Properties of Semiconductors were included in this presentation at the CIPI-S/NIT Toronto Summer School (June 2005).

Some of the key papers on our research into nonlinear refraction in AlGaAs and its applications:

  • J. S. Aitchison, D. C. Hutchings, J. U. Kang, G. I. Stegeman and A. Villeneuve, “The Nonlinear Optical
    Properties of AlGaAs at the Half-Band-Gap”, IEEE J. Quantum Electron. 33, 341–348 (1997).
  • J. S. Aitchison, A. H. Kean, C. N. Ironside, A. Villeneuve, and G. I. Stegeman, "Ultrafast all-optical switching in Al0.18Ga0.82As directional coupler in 1.55 μm spectral region", Electron. Lett. 27, 1709-1710 (1991).
  • K. Al-Hemyari, J. S. Aitchison, C. N. Ironside, G. T. Kennedy, R. S. Grant, and W. Sibbett,  "Ultrafast all-optical switching in GaAlAs integrated interferometers in the 1.55 μm spectral region",  Electron. Lett.,  vol. 28,  pp.1090 -1092 1992.
  • J. S. Aitchison, K. Al Hemyari, C. N. Ironside, R. S. Grant, and W. Sibbett,  "Observation of spatial solitons in AlGaAs waveguides",  Electron. Lett.,  vol. 20,  pp.1879 -1880 1992.
  • D. C. Hutchings and B. S. Wherrett, “Theory of the Dispersion of Ultrafast Nonlinear Refraction in Zinc-
    Blende Semiconductors below the Band Edge”, Phys. Rev. B 50, 4622–4630 (1994).
  • D. C. Hutchings and B. S. Wherrett, “Theory of the Anisotropy of Ultrafast Nonlinear Refraction in Zinc-
    Blende Semiconductors”, Phys. Rev. B 52, 8150–8159 (1995).
  • D. C. Hutchings, J. S. Aitchison, B. S. Wherrett, G. T. Kennedy and W. Sibbett, “Polarisation dependence
    of ultrafast nonlinear refraction in an AlGaAs waveguide at the half-band-gap”, Optics Lett. 20 991–993
  • J. S. Aitchison, A. Villeneuve, and G. I. Stegeman,  "Nonlinear directional couplers in AlGaAs",  J. Nonlinear Opt. Phys. Mater.,  vol. 4,  pp.871 -891 1995
  • C. J. Hamilton, B. Vogele, J. S. Aitchison, G. T. Kennedy, W. Sibbett, W. Biehlig, U. Peschel, T. Peschel, and F. Lederer,  "Bright solitary pulses in AlGaAs waveguides at half-the-band-gap",  Opt. Lett.,  vol. 21,  pp.1226 -1228 1996
  • J. U. Kang, G. I. Stegeman, and J. S. Aitchsion,  "One-dimensional spatial soliton dragging, trapping and all-optical switching in AlGaAs waveguides",  Opt. Lett.,  vol. 21,  pp.189 -191 1996
  • D. C. Hutchings, J. M. Arnold, and D. F. Parker, “Stationary mixed-polarisation spatial solitons and their
    stability in semiconductor waveguides”, Phys. Rev. E 58, 6649–6658 (1998).