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

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.

Structuring Nonlinear Wavefront Emitted from Monolayer Transition-Metal Dichalcogenides

“…In the past decade, nonlinear signals (second-and thirdharmonic generation, SHG and THG) from nanomaterials and artificially structured materials, namely, metamaterials and metasurfaces, have attracted extensive attention for their wavelength tunability, coherence, and ultrafast responses [1][2][3][4][5][6]. These materials show promising applications in nanoprobing [1], imaging [2,3], and crystalline detection [4][5][6].…”

“…In the past decade, nonlinear signals (second-and thirdharmonic generation, SHG and THG) from nanomaterials and artificially structured materials, namely, metamaterials and metasurfaces, have attracted extensive attention for their wavelength tunability, coherence, and ultrafast responses [1][2][3][4][5][6]. These materials show promising applications in nanoprobing [1], imaging [2,3], and crystalline detection [4][5][6]. Compared with the control of linear optical signals with a metasurface [7][8][9][10][11][12][13][14], the wavefront engineering and control of generated nonlinear signals are the most challenging task to realizing integrated, ultrathin, and efficient nonlinear optical devices, ranging from nonlinear beam steering [15,16], nonlinear metalenses [17,18], nonlinear holography [19,20], optical image encoding [21], and the generation of a nonlinear optical vortex beam [22][23][24].…”

Anomalously Strong Second‐Harmonic Generation in GaAs Nanowires via Crystal‐Structure Engineering

“…Due to a large surface‐to‐volume ratio, utilizing nanostructures, for example, nanowires (NWs), for such applications not only is important for efficient miniaturization but also allows one to tailor and enhance the nonlinear response. [ 10–30 ] Considering that a dielectric NW represents a naturally formed cavity, strong localization of the fundamental light and highly directional SHG can be achieved due to Mie resonances caused by interference of the cavity modes, [ 10 ] and also by integrating the dielectric NWs into plasmonic structures. [ 27,31–34 ] An additional degree of freedom in the engineering of the SHG response is provided by the ability to grow NWs with different lattice structures and, therefore, to explore nonlinearity of crystallographic polytypes that cannot be fabricated in bulk under conventional growth conditions.…”

Polarity-dependent nonlinear optics of nanowires under electric field

“…This method, known as electric-field-induced second harmonic (EFISH), was first demonstrated for calcite 40 . The same principle can be applied to non-centrosymmetric crystals such as CdS 41 and GaAs 42 by applying an electric field along the nonpolar [1 10] direction of the WZ structure or the [001] direction of the ZB structure, where SHG is symmetry forbidden. However, to the best of our knowledge, the modulation of SHG along the polar axis of nanostructures by an external electric field due to interference between the static SHG and EFISH component has not yet been reported, and the ability to exploit this phenomenon as a tool to determine polarity has not yet been demonstrated.…”