Strong modulation of second-harmonic generation with very large contrast in semiconducting CdS via high-field domain

Ming-Liang Ren,Gerui Liu,Jacob S Berger,Wenjing Liu,Ritesh Agarwal

doi:10.1038/s41467-017-02548-3

Ming-Liang Ren, Gerui Liu + Show 3 more

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https://doi.org/10.1038/s41467-017-02548-3

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Journal: Nature Communications	Publication Date: Jan 15, 2018
Citations: 26	License type: open-access

Affiliation: University of Pennsylvania

Abstract

Dynamic control of nonlinear signals is critical for a wide variety of optoelectronic applications, such as signal processing for optical computing. However, controlling nonlinear optical signals with large modulation strengths and near-perfect contrast remains a challenging problem due to intrinsic second-order nonlinear coefficients via bulk or surface contributions. Here, via electrical control, we turn on and tune second-order nonlinear coefficients in semiconducting CdS nanobelts from zero to up to 151 pm V−1, a value higher than other intrinsic nonlinear coefficients in CdS. We also observe ultrahigh ON/OFF ratio of >104 and modulation strengths ~200% V−1 of the nonlinear signal. The unusual nonlinear behavior, including super-quadratic voltage and power dependence, is ascribed to the high-field domain, which can be further controlled by near-infrared optical excitation and electrical gating. The ability to electrically control nonlinear optical signals in nanostructures can enable optoelectronic devices such as optical transistors and modulators for on-chip integrated photonics.

Highlights

Dynamic control of nonlinear signals is critical for a wide variety of optoelectronic applications, such as signal processing for optical computing
To study dynamically controlled second-harmonic generation (SHG), we fabricated two-terminal devices on a single-CdS nanobelt with a d.c. electric field applied along the
CdS a-axis, with optical excitation via the fundamental wave (FW) polarized along the CdS x-axis, with crystallographic axes confirmed via SHG polarimetry (Supplementary Fig. 1)[12]

Summary

Introduction

Dynamic control of nonlinear signals is critical for a wide variety of optoelectronic applications, such as signal processing for optical computing. Controlling nonlinear optical signals with large modulation strengths and near-perfect contrast remains a challenging problem due to intrinsic second-order nonlinear coefficients via bulk or surface contributions. EFISH was first observed in a bulk calcite crystal in 19626, in which a strong electric field (Fl) was applied to break structural inversion symmetry and induce effective secondorder nonlinear coefficients χðij2kÞð2ω; ω; ω; 0Þ by interacting with third-order nonlinear coefficients χðij3kÞlð2ω; ω; ω; 0Þ. Electrolyte, it is challenging to switch bulk second-order nonlinear coefficients from zero to very-large values (e.g., >100 pm V−1), let alone in semiconductors, which typically have a large density of free carriers It would be desirable if new nonlinear coefficients could be obtained in semiconductors with perfect contrast and strong modulation strengths, via controlling the unique electric field profile, to enable their use for practical applications and integration with other on-chip electronic/photonic devices.

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