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Adv Mater. 2017 Jul;29(27). doi: 10.1002/adma.201700754. Epub 2017 May 3.

A Solution-Processed Ultrafast Optical Switch Based on a Nanostructured Epsilon-Near-Zero Medium.

Guo Q1,2, Cui Y2,3, Yao Y4, Ye Y1, Yang Y1, Liu X2,3, Zhang S4, Liu X1,2, Qiu J2,3, Hosono H5.

Author information

1
Institute of Inorganic Materials, School of Materials Science & Engineering, Zhejiang University, Hangzhou, 310027, China.
2
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, 310027, China.
3
College of Optical Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
4
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China.
5
Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.

Abstract

All the optical properties of materials are derived from dielectric function. In spectral region where the dielectric permittivity approaches zero, known as epsilon-near-zero (ENZ) region, the propagating light within the material attains a very high phase velocity, and meanwhile the material exhibits strong optical nonlinearity. The interplay between the linear and nonlinear optical response in these materials thus offers unprecedented pathways for all-optical control and device design. Here the authors demonstrate ultrafast all-optical modulation based on a typical ENZ material of indium tin oxide (ITO) nanocrystals (NCs), accessed by a wet-chemistry route. In the ENZ region, the authors find that the optical response in these ITO NCs is associated with a strong nonlinear character, exhibiting sub-picosecond response time (corresponding to frequencies over 2 THz) and modulation depth up to ≈160%. This large optical nonlinearity benefits from the highly confined geometry in addition to the ENZ enhancement effect of the ITO NCs. Based on these ENZ NCs, the authors successfully demonstrate a fiber optical switch that allows switching of continuous laser wave into femtosecond laser pulses. Combined with facile processibility and tunable optical properties, these solution-processed ENZ NCs may offer a scalable and printable material solution for dynamic photonic and optoelectronic devices.

KEYWORDS:

colloidal nanocrystals; epsilon-near-zero; optical modulation; tunable optical properties; ultrafast photonics

PMID:
28466957
DOI:
10.1002/adma.201700754

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