Second harmonic generation enhancement from a nonlinear nanocrystal integrated hyperbolic metamaterial cavity

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Whispering-gallery modes (WGMs) are crucial for light confinement in resonant cavities.
• Metamaterials offer unique optical properties through engineered structures.
• Plasmonic nanostructures are explored for enhancing light-matter interactions.

Purpose of the Study:

• To theoretically investigate dipolar whispering-gallery modes (WGMs) in spherical hyperbolic metamaterial (HMM) cavities.
• To explore the field enhancement capabilities of HMM cavities with different WGM orders.
• To demonstrate the potential of HMM cavities for nonlinear optical processes like second harmonic generation (SHG).

Main Methods:

• Theoretical analysis of WGMs in multilayered spherical HMMs.
• Simulation of local field distributions within the dielectric core.
• Investigation of the effect of metal filling ratio on resonant wavelengths.
• Integration of a nonlinear nanocrystal model to calculate SHG enhancement.

Main Results:

• HMM cavities support dipolar WGMs with distinct mode orders.
• Highest order WGMs generate highly enhanced and uniform local fields in the dielectric core.
• Resonant wavelengths are tunable over a wide spectral range by adjusting the metal filling ratio.
• SHG intensity enhancement up to 3.9 × 10¹⁰ is achieved, significantly outperforming single-layer plasmonic cavities.

Conclusions:

• Spherical HMM cavities are effective platforms for generating enhanced and uniform local fields via WGMs.
• The metal filling ratio provides a facile method for tuning optical resonances.
• HMM cavities offer unprecedented enhancement for nonlinear optical processes, particularly SHG, by integrating nanocrystals.