Research ArticlePHYSICS

Ultrafast sub–30-fs all-optical switching based on gallium phosphide

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Science Advances  14 Jun 2019:
Vol. 5, no. 6, eaaw3262
DOI: 10.1126/sciadv.aaw3262


Gallium phosphide (GaP) is one of the few available materials with strong optical nonlinearity and negligible losses in the visible (λ > 450 nm) and near-infrared regime. In this work, we demonstrate that a GaP film can generate sub–30-fs (full width at half maximum) transmission modulation of up to ~70% in the 600- to 1000-nm wavelength range. Nonlinear simulations using parameters measured by the Z-scan approach indicate that the transmission modulation arises from the optical Kerr effect and two-photon absorption. Because of the absence of linear absorption, no slower free-carrier contribution is detected. These findings place GaP as a promising ultrafast material for all-optical switching at modulation speeds of up to 20 THz.

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