Power transfer mechanism of metallic grating coupled whispering gallery microsphere resonator

Abstract

The power transfer mechanism of the Fano resonance in a metallic grating coupled whispering gallery microsphere resonator is both theoretically investigated and experimentally verified. Based on temporal coupled mode theory, a two-stage cascaded scattering model is formulated to account for the power interaction of multiple resonances in the system. The modeled results show agreement with experimental measurements and are able to explain several counter-intuitive observations in the spectra. The coupling efficiency of the grating coupler is evaluated at critical coupling by approximating symmetric resonance line-shape with grating design. Based on the modeled results, it is found that the coupling efficiency can be further improved by enhancing diffraction efficiency of the first-order diffractions.

Fabrication and spectral characterizations of high Q asymmetric resonant cavities

“…Fig. 5(b) shows the coupling efficiency of ARCs and its corresponding microspheres,which is the key factor for the limit sensitivity of ROG [26].The coupling efficiency of ACRs remains around 70% calculated using formula [27], which is the same as microsphere. Thus, compare to the corresponding microsphere, the ARC with deformation degree η¼8% holds the same scale Q-values and coupling efficiency, but a single spectrum peak (fundamental mode).…”

The Distribution and Evolution of Refractive Index in a Polystyrene Whispering Gallery Microcavity during Glass Transition

“…The diffraction grating had been demonstrated as an effective coupler for the excitation of WGMs in microspheres. [34][35][36][37] Compared with the coupling setup of micro-prisms, tapers, and waveguides, [38][39][40][41] the diffraction grating was a planar film-like object, as thin as hundreds of nanometers, and its area could be as small as 10 × 10 µm 2 , which made it suitable for integration. Furthermore, both the fundamental and high-order radial WGMs of the microspheres could be easily excited by adjusting the period of a diffraction grating.…”