Atomic Layer Deposition for Enhanced Light Confinement in Nonlinear Metasurfaces.

Area of Science:

• Nanophotonics and Metasurface Engineering
• Nonlinear Optics
• Materials Science

Background:

• Metasurfaces offer strong nonlinear optical responses through nanoantenna resonances.
• Conventional nonlinear materials have moderate refractive indices, limiting mode localization.
• High-refractive-index materials enhance mode confinement but often require high-temperature processing.

Purpose of the Study:

• To enhance mode confinement in nonlinear metasurfaces.
• To develop a low-temperature atomic layer deposition (ALD) process for conformal titania coatings.
• To improve nonlinear signal generation in the near-infrared (NIR) wavelength range.

Main Methods:

• Development of a low-temperature ALD process for titania conformal coatings.
• Design of a metasurface integrating a nonlinear crystal with an ALD titania coating.
• Numerical simulations to optimize ALD coating thickness for enhanced mode localization and nonlinear effects.

Main Results:

• Achieved enhanced mode confinement in nonlinear metasurfaces using titania ALD coatings.
• Demonstrated significant enhancement in second-harmonic generation (SHG) through optimized ALD thickness.
• Validated the low-temperature ALD process for materials sensitive to high temperatures, including polymers.

Conclusions:

• Conformal titania ALD coatings effectively enhance mode confinement and nonlinear optical responses in metasurfaces.
• The developed low-temperature ALD technique broadens the applicability of metasurface nonlinearities to a wider range of materials.
• Optimized metasurface designs show promise for efficient nonlinear signal generation in the telecommunication wavelength range.