Free carrier induced spectral shift for GaAs filled metallic hole arrays.

For a GaAs filled metallic hole array on a pre-epi GaAs substrate, the free carriers, generated by three-photon absorption (3PA) assisted by strongly enhanced local fields, reduce the refractive index of GaAs in ~200-nm thick active area through band filling and free carrier absorption. Therefore, the surface plasma wave (SPW) resonance, and the related second harmonic (SH) spectrum blue shifts with increasing fluence; For the plasmonic structure on a substrate with surface defects, free carrier recombination dominates. The band gap emission spectral peak wavelength decreases 10-nm with increasing fluence, showing the transition from nonradiative-, at low excitation, to bimolecular-recombination at high carrier concentrations.