Analysis of induced-transparency in an original three-order resonator system

For the application requirements of resonant micro-cavity, an original three-ring resonant micro-cavity structure is proposed in this paper. Like electromagnetically induced transparency in an atomic system, the coupled resonator-induced transparency (CRIT) phenomenon in a new optical micro-cavity system is proven experimentally. Up to now, most of the resonators based on CRIT are just in the theoretical exploration stage, and the analysis of the double-ring structure has been relatively common. The CRIT effect of a resonator has a significant relationship with the coupler insertion loss, the ring circumference, and the multiples of the rings, which need high requirements in the structural design and preparation process. In order to reduce the difficulty in design and preparation, we propose a new three-ring cascade resonator structure with the same cavity size on silicon. According to the transfer matrix method and coupled mode theory, we find a CRIT effect after theoretical analysis. Our devices are fabricated on an SOI wafer. By using the micro-cavity measurement platform to repeat and analyze the tests of single ring and three-ring cascade resonator structure, we obtain a grating coupler efficiency of 30%. By applying the antireflection coating, the coupling efficiency of the grating coupler is up to 34%. During the test, the mutual interference between annular cavities of the three-ring resonators produces two transmission peaks, the output spectrum of the resonator with a narrow transparency peak at a low group velocity, which is verified in CRIT phenomenon. Compared with the traditional single-ring structure, the resonator has a quality factor increasing four times, reaching a value of up to 0.65 × 10⁵, the through and drop transmission spectra of the resonator are reconciled well with each other. At the same time, in order to obtain the sensitivity of the resonator to temperature, we conduct tuning tests of the resonator temperature characteristics, the resonant peak is moved to the large wavelength direction with temperature increasing, and detuning wavelength of the resonance can be controlled by changing temperature, which is called red-shift. Therefore, the original three-ring cascaded resonators have significant applications in the rotation sensing, optical filters, optical storage and temperature sensing elements.