Sum-Frequency Generation in High-Q GaP Metasurfaces Driven by Leaky-Wave Guided Modes.

Area of Science:

• Optics and Photonics
• Materials Science
• Nonlinear Optics

Background:

• Resonant metasurfaces offer potential for enhancing multiwave nonlinear optical interactions.
• Challenges in mode matching and material transparency limit current metasurface applications for nonlinear processes.

Purpose of the Study:

• To demonstrate efficient nonlinear sum-frequency generation (SFG) in multiresonant gallium phosphide (GaP) metasurfaces.
• To explore the use of guided-wave bound-state in the continuum (BIC) resonances for enhanced nonlinear optical processes.
• To investigate the polarization dependence of SFG and its potential for controlling emission direction.

Main Methods:

• Fabrication of multiresonant GaP metasurfaces utilizing guided-wave BIC resonances.
• Excitation of the metasurface with two near-infrared input beams.
• Characterization of the generated sum-frequency signal in the visible spectrum and analysis of polarization effects.

Main Results:

• Achieved a high SFG conversion efficiency of 2.5 × 10^-4 W^-1, significantly outperforming Mie-type resonant metasurfaces.
• Observed a non-trivial polarization dependence, with enhanced SFG using non-parallel polarized input beams.
• Demonstrated control over SFG emission direction by varying the input pump beam polarization.

Conclusions:

• Multiresonant GaP metasurfaces based on BIC resonances enable highly efficient nonlinear SFG.
• The demonstrated polarization control opens new avenues for designing advanced nonlinear light sources.
• This work facilitates efficient infrared to visible light conversion with potential applications in optical technologies.