Optical nonlinearity in semiconductor nanowaveguides

Semiconductor nanostructures have great promise for applications such as nonlinear optics, sensing, and life sciences. In nanowaveguides, both the strong optical nonlinearity of semiconductors and the light localization can be applied for nonlinear scanning microscopy, novel nanoscopic light sources, and active nonlinear elements in future nanophotonic devices.

The second-harmonic generation (SHG) is a particular case of nonlinear optical wave mixing utilizing non-centrosymmetric crystals. However, at the surface, both structural and optical filed discontinuities can contribute to SHG, which can also be observed in centrosymmetric crystals (e.g. in silicon). The structural discontinuity breaks the symmetry at the surface, whereas the optical field discontinuity present at the interface of two materials with different refractive indices leads to quadrupole contribution to surface SHG. Therefore in semiconductor nanostructures with large refractive index contrast both effects should be considered in addition to the bulk nonlinearity.

In this seminar, I will give an introduction to surface optical nonlinearity and discuss both the surface and the bulk contribution to nonlinear phenomena in semiconductor nanowaveguides.