Abstract
In this report, we propose and demonstrate an air-mode photonic crystal ring resonator (PhCRR) on silicon-on-insulator platform. Air mode is utilized to confine the optical field into photonic crystal (PhC) air holes, which is confirmed by the three-dimensional finite-difference time-domain simulation. PhCRR structure is employed to enhance the light-matter interaction through combining the whispering-gallery mode resonance of ring resonator with the slow-light effect in PhC waveguide. In the simulated and measured transmission spectra of air-mode PhCRR, nonuniform free spectral ranges are observed near the Brillouin zone edge of PhC, indicating the presence of the slow-light effect. A maximum group index of 27.3 and a highest quality factor of 14600 are experimentally obtained near the band edge. Benefiting from the strong optical confinement in the PhC holes and enhanced light-matter interaction in the resonator, the demonstrated air-mode PhCRR is expected to have potential applications in refractive index sensing, on-chip light emitting and nonlinear optics by integration with functional materials.
Highlights
In this report, we propose and demonstrate an air-mode photonic crystal ring resonator (PhCRR) on silicon-on-insulator platform
Air mode is utilized to confine the optical field into photonic crystal (PhC) air holes, which is confirmed by the three-dimensional finite-difference time-domain simulation
Distinct from the dielectric-mode PhCRR, optical field is strongly squeezed into the PhC holes and overlaps sufficiently with the analyte in the air-mode PhCRR, which further improves the sensitivity of PhCRR structure
Summary
When approaching the Brillouin zone edge, the decrease in FSRs from 3.31 to 0.95 nm indicates the large group index dispersion and strong slow-light effect. From the above measured and simulated transmission spectra of the air-mode PhCRR in Fig. 2(b) and 3(a), the group index can be calculated by taking ng ≈ λ 2/(FSR·L), where ng is the group index, λ is the central wavelength between two adjacent resonances, and L is the round-trip path-length of the ring. We have proposed and demonstrated an air-mode PhCRR on silicon-on-insulator In such type of PhCRR, optical field can be strongly confined in PhC air holes, proven by the 3D FDTD simulated band-edge resonant mode profiles. As wavelength approaches the Brillouin zone edge, the transmission spectrum of the PhCRR exhibits a decreasing FSR, indicating the presence of the slow-light effect. The combination of the strong optical confinement in air holes, the slow-light effect and the WGM resonance would greatly enhance the light-matter interaction in air holes, which makes the air-mode PhCRR potential for applications in RI sensing, on-chip light emitting and nonlinear optics
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