Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 21: Photonic Crystals I

HL 21.1: Vortrag

Montag, 26. März 2012, 17:00–17:15, EW 203

Spectral compression of light by ultrafast tilting of the dispersion of a photonic crystal — •Tobias Kampfrath^1,2, Daryl Beggs², Thomas Krauss³, and L. Kuipers² — ¹Fritz Haber Institute of the Max Planck Society, Berlin, Germany — ²FOM Institute AMOLF, Amsterdam, The Netherlands — ³University of St. Andrews, Scotland, UK

Photonic crystals are well known for their ability to control the dispersion relation ω(k) of light. Here, we demonstrate that ω(k) can even be tuned on ultrafast timescales by means of a femtosecond pump pulse exciting the silicon parts of a photonic-crystal waveguide. We shape the cross section of the pump beam with a nanometric shadow mask such that different waveguide eigenmodes acquire different spatial overlap with the perturbing pump. In this way, a local flattening of the dispersion curve by as much as 11 % is obtained. This value is two orders of magnitude higher than the relative pump-induced variations Δ n/n of the silicon refractive index.

We show that such partial mode perturbation can be used to adiabatically compress the spectrum of a light pulse traveling through the waveguide.