Q Factors Exceeding 10⁴ in Wavelength-to-Subwavelength-Scale Free-Space Resonators with Dual Asymmetry Control

Area of Science:

• Photonics
• Nanotechnology
• Materials Science

Background:

• High quality factors (Q) and small mode volumes (Vm) are crucial for enhancing light-matter interactions in optical resonators.
• Current designs are limited to Q factors of ~10^3 due to coupled geometric and optical perturbations.
• Accessing ultrahigh-Q regimes in free-space-addressable resonators remains a significant challenge.

Purpose of the Study:

• To present a novel biaxial framework for designing optical resonators with independently tunable asymmetry axes.
• To overcome the limitations of existing designs and achieve ultrahigh Q factors at subwavelength mode volumes.
• To establish a generalizable strategy for creating advanced nanophotonic resonators.

Main Methods:

• Demonstrated the biaxial framework using very-large-scale-integrated Silicon nanoantenna pixel (VINPix) resonators.
• Utilized out-of-plane perturbations with amorphous Si, SiNx, and SiO2.
• Experimentally characterized resonator performance in arrays of over 80 resonators in water.
• Employed computational methods to explore slotted VINPix resonators for even higher Q factors.

Main Results:

• Achieved experimental Q factors up to 76,000 at Vm of ~1.7 λ0^3*neff^-3.
• Demonstrated iso-Q contours connecting distinct geometric and optical perturbations.
• Computationally predicted Q factors exceeding 10^6 at Vm of ~0.2 λ0^3*neff^-3 for slotted VINPix resonators.

Conclusions:

• The biaxial framework unlocks a new radiative landscape, enabling independent tuning of geometric and optical perturbations.
• This approach provides a generalizable design strategy for ultrahigh-Q free-space nanophotonic resonators.
• The demonstrated VINPix resonators show significant potential for applications in sensing, nonlinear optics, and quantum photonics.