Directly grown crystalline gallium phosphide on sapphire for nonlinear all-dielectric nanophotonics

Abstract

Efficient second harmonic generation (SHG) in nanophotonic designs based on all-dielectric nanostructures demands materials with large values of the quadratic nonlinear susceptibility, low dissipative losses, and high refractive index. One of the best materials meeting all these parameters is gallium phosphide (GaP). However, second-order nonlinearity requires high crystallinity and morphology quality of the GaP layer grown for further lithographic processing. Here we develop a method to fabricate high-quality crystalline GaP metasurfaces, which demonstrate pronounced linear and nonlinear optical properties. Direct growth of a GaP layer on a sapphire substrate tackles the previous problem of wafer bonding, because of high optical contrast between fabricated resonant nanoparticles and the substrate. As a result, the fabricated GaP metasurface supports bound state in continuum mode with an experimental quality factor around 100 yielding a strong enhancement of SHG in narrow spectral range. We believe that the developed approach will become a versatile platform for nonlinear all-dielectric nanophotonics.

Anisotropic Radiation in Heterostructured “Emitter in a Cavity” Nanowire

“…GaP is a low-loss material with the near-zero imaginary part of the refractive index. However, for the provided wavelengths, the real part of the refractive index decreases from 3.4 (650 nm) to 3.1 (1300 nm) [52]. This affects the directivity of the NW: as the wavelength increases, the light coupling in the NW reduces with the corresponding fall of the emission directed toward the edges.…”

Broadband Optical Constants and Nonlinear Properties of SnS2 and SnSe2

“…As shown in Figure 6 , SnS 2 meets both requirements since it possesses a refractive index n ≈ 2.8 and zero extinction in the visible and infrared ranges. More importantly, SnS 2 could even compete with classical high refractive index materials such as Si, GaP, and TiO 2 [ 65 , 66 , 67 , 68 ]. In particular, SnS 2 has a wider transparency region compared with GaP and Si and a larger refractive index than TiO 2 ( Figure 6 ).…”

Nonlinear Dielectric Nanoantennas and Metasurfaces: Frequency Conversion and Wavefront Control

“…107,108 Their interaction increases the damping rate of one of the modes, while that of the other decreases until it nearly vanishes and the quasi-BIC emerges. Experimental demonstrations of SHG on the nanoscale through high-Q quasi-BICs have been performed in GaP metasurfaces 58,59 and AlGaAs single nanodisks. 51 Figure 2e schematizes the unit cell of the GaP metasurface studied by Anthur et al 58 and the optical modes involved in the quasi-BIC formation.…”

“…It relies on the second order nonlinear susceptibility, χ (2) , which acts as a third-rank tensor when considering the vectorial nature of the fields. In the electric dipole approximation of light–matter interaction, all elements of χ (2) vanish in uniform media with a centrosymmetric crystal structure, channeling most of the research on SHG in nanostructured dielectrics toward the use of high-index ( n > 3) noncentrosymmetric III–V semiconductors, such as GaAs, ,− AlGaAs, − and GaP. − The basic optical properties of these three compounds are presented in Table , including their transparency range, refractive index, and nonzero independent elements of χ (2) in the contracted notation (assuming the Kleinman symmetry condition). All these semiconductors possess a zincblende crystal structure with a cubic symmetry described by the 4̅3 m point group, making χ 36 (2) the only nonzero independent element of χ (2)…”

“…Experimental demonstrations of SHG on the nanoscale through high- Q quasi-BICs have been performed in GaP metasurfaces , and AlGaAs single nanodisks Figure e schematizes the unit cell of the GaP metasurface studied by Anthur et al and the optical modes involved in the quasi-BIC formation.…”