Spectral stability of bound state in the continuum resonances due to thermal effect and the application as efficient thermo-optic modulators

Abstract

The phenomenon of bound state in the continuum (BIC) has raised ever-increasing research interest as a new means of manipulating light–matter interactions. The ultra-high quality factors associated with BIC resonances also make them very vulnerable to any environmental turbulence. For example, very weak changes of the refractive index may lead to large spectral shift. In this work, we numerically investigate the spectral stability of the quasi-BIC resonances due to temperature changes supported by all-dielectric optical nanoantennas in the form of slotted silicon disk array. We find that due to the extremely-high quality factor of the quasi-BIC mode, the resonance is very sensitive to ambient temperatures with a wavelength shift rate around 0.077 nm/K, resulting from the thermo-optic effect of the constituent materials. This effect of thermal tunability can nevertheless be utilized to achieve an efficient thermo-optic modulator and we demonstrate that the transmittance at the original resonance frequency will change from 0 to 1 when the temperature increases by only 5 Kelvin, using an experimentally obtained thermo-optic coefficient of silicon and fused silica as 1.8 × 10−4/K and 8.5 × 10−6/K respectively.