Advancements in Sub-Diffractive Optical Resonators
Recent advancements in optical technology have been made with the development of all-dielectric silicon microring resonators that achieve deeply sub-diffractive mode volumes. This innovative approach utilizes nanostructured subwavelength metamaterial waveguides and focuses on the excitation of standing wave resonances rather than the traditional traveling wave whispering gallery mode (WGM) resonances. The result is a significant reduction in mode volume by factors ranging from 10 to 100 compared to conventional diffraction-limited silicon microring resonators.
The authors, Saddam Gafsi and Judson D. Ryckman, highlight a critical finding regarding the scaling of the sub-diffractive mode volume. They propose a lower limit for the mode volume, denoted as Vmin', which is proportional to the mode order multiplied by the refractive index raised to the seventh power (Vmin' ∼ m n-7). This relationship suggests that as the mode order increases, the potential for further miniaturization of optical devices also increases.
Through both numerical modeling and experimental characterization, the researchers systematically explored the modal properties of these metawaveguide ring resonators made from silicon (Si) and silicon dioxide (SiO2). The experimental results demonstrated that these sub-diffractive devices can support standing wave resonances with high intrinsic quality factors, ranging from 104 to 105.
The implications of this research are significant for the field of optics, particularly in the integration of wavelength-scale optics with sub-wavelength matter. The findings indicate a promising platform for future applications in photonics, potentially leading to more efficient and compact optical devices.
For further details, the full paper titled "All-dielectric silicon microring resonators with deeply sub-diffractive mode volumes" can be accessed at arXiv:2408.13445.