Giant Enhancement of Continuous Wave Second Harmonic Generation from Few-Layer GaSe Coupled to High-Q Quasi Bound States in the Continuum

Abstract

Two-dimensional (2D) layered materials such as GaSe recently have emerged as novel nonlinear optical materials with exceptional properties. Although exhibiting large nonlinear susceptibilities, the nonlinear responses of 2D materials are generally limited by the short interaction lengths with light, thus further enhancement via resonant photonic nanostructures is highly desired for building high-efficiency nonlinear devices. Here, we demonstrate a giant second-harmonic generation (SHG) enhancement by coupling 2D GaSe flakes to silicon metasurfaces supporting quasi-bound states in the continuum (quasi-BICs) under continuous-wave (CW) operation. Taking advantage of both high-quality factors and large mode areas of quasi-BICs, SHG from a GaSe flake is uniformly enhanced by nearly 4 orders of magnitude, which is promising for high-power coherent light sources. Our work provides an effective approach for enhancing nonlinear optical processes in 2D materials within the framework of silicon photonics, which also brings second-order nonlinearity associated with 2D materials to silicon photonic devices.

Efficient Second‐Harmonic Generation from Silicon Slotted Nanocubes with Bound States in the Continuum

“…The experimentally measured SHG efficiency of the silicon slotted nanocube array is high as 1.8 × 10 −4 W −1 , which could be further engineered by modifying the air‐slot geometries, such as the width and depth of the air‐slot, and the shift of the air‐slot from the nanocube center. Moreover, recently emerged strategies, including doubly resonant enhancement [ 31,32 ] and the integration with 2D materials, [ 58 ] provide novel approaches to further boost the SHG. As more strategies are proposed, we believe that the surface SHG effect in silicon nanostructures can be further improved.…”

Polarization-controlled dynamically switchable high-harmonic generation from all-dielectric metasurfaces governed by dual bound states in the continuum

“…Finally, it is worth pointing out that the strategy and structure here are rather general, and can be extended for the selective enhancement of other nonlinear effects at alternative wavelengths via physical scalability 64,65 . One example that comes to mind may be the polarization-controlled harmonic generation and sum-frequency mixing in 2D materials [66][67][68][69][70] .…”

Engineering van der Waals Materials for Advanced Metaphotonics

“…589,1248,1250 Therefore, it could be beneficial in developing all-dielectric platforms for EIT metadevices in future especially in experiment, for example, based on all-dielectric metasurfaces. 1107,1108 However, to the best of our knowledge, experimental demonstration of ultrahigh Q-factor EIT resonance based on a combination of all-dielectric metasurfaces and 2D materials remains yet to be explored. Another challenge of 2D materials EIT metadevices is that current experimental demonstrations have been limited to linear polarization.…”