Fig. 1. (a) WGM schematic diagram. (b) Resonance wavelengths as a function of polar mode numbers in a single WGMR with R=2.4  mm and ρ=0.05R. The red and blue colors indicate q=1 and q=2 radial modes, respectively. Resonance wavelength as a function of the radius for (c) different radial modes with l=20,770 and p=0 and (d) different angular modes with l=20,770 and q=1.

Fig. 2. Schematic illustration of a resonator with two WGMs.

Fig. 3. (a) LN WGMR with copper electrodes. (b) Schematic of the experimental setup. An LN WGMR is coupled to a rutile prism. HWP, half-wave plate; and PD, photodetector.

Fig. 4. (a)–(e) Normalized experimental transmission spectrum changes with increasing voltage. The pink arrow indicates mode 1, while the blue arrow indicates mode 2. (f) Zoom-in for the normalized transmission of adjacent modes 1 and 2, corresponding to the green box in Fig. 3(a). (g) Resonance wavelength shifts of two modes as a function of the applied voltage.

Fig. 5. (a)–(e) Experimental data for the normalized transmission spectra of the LN WGM coupled via a rutile prism at different voltages. From the top panel to the bottom panel, the voltage changes from 0 V to 160 V, at intervals of 40 V. (f), (g) Theoretical calculation of the spectrum of the coupled system. The theoretical parameters are: [k0A,k1A,k0B,k1B,g,ΔωAB]=[0.95π,11π,−9.6π,−0.17π,0.03π,−105]  MHz, [0.95π,11.8π,−9.6π,−0.4π,0.44π,−46]  MHz, [0.95π,10.8π,−9.6π,−0.5π,0.2π,0]  MHz, [0.95π,11.2π,−9.6π,−0.4π,0.14π,24]  MHz, and [0.95π,10π,−9.6π,−0.14π,1.8π,145]  MHz.