Presentation
17 September 2018 Ultrafast dynamics and spectral dependence of optical nonlinearities in doped semiconductors at epsilon-near-zero (Conference Presentation)
Author Affiliations +
Abstract
Materials where the real part of the permittivity is near zero are known to have interesting nonlinear optical properties such as enhanced harmonic generation and large nonlinear refraction (NLR). In particular, the NLR of highly doped semiconductors such as Indium Tin Oxide and Aluminum doped Zinc Oxide is enhanced in the near-infrared spectral regions, where the real part of the permittivity crosses zero, the precise wavelength of which can be tuned by controlling the doping level.. This is also known as the epsilon near zero (ENZ) regime, although the imaginary part of the permittivity is not necessarily small at this wavelength. In order to characterize these nonlinearities, we use the Beam-Deflection (BD) method to directly characterize the temporal dynamics and polarization dependence of the nondegenerate NLR and nonlinear absorption of doped semiconductors at ENZ. BD has sensitivity to induced optical path length as small as 1/20,000 of a wavelength, which enables us to resolve NLR in the presence of large nonlinear absorption backgrounds. The BD technique also allows separation of instantaneous bound electronic nonlinearities from non-instantaneous mechanisms such as the carrier redistribution effects that dominate in ENZ materials,. We can also study the dependence on relative polarization and incidence angle of excitation and probe waves. Our method also reveals the effect of tuning the wavelength of excitation or probe waves through ENZ separately and we find that that the strong wavelength dependence of nonlinearities around the ENZ point is quite different for pump and probe waves.
Conference Presentation
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Sepehr Benis, Eric W. Van Stryland, and David J. Hagan "Ultrafast dynamics and spectral dependence of optical nonlinearities in doped semiconductors at epsilon-near-zero (Conference Presentation)", Proc. SPIE 10719, Metamaterials, Metadevices, and Metasystems 2018, 1071910 (17 September 2018); https://doi.org/10.1117/12.2321983
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KEYWORDS
Nonlinear optics

Semiconductors

Ultrafast phenomena

Absorption

Polarization

Harmonic generation

Indium

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