Versatile Metamaterial: Exploring the Resonances of Symmetry-Protected Modes for Multitasking Functionality

In this work, an experimental study supported by numerical modeling that demonstrates the possibility of exciting Symmetry Protected-Bound states In the Continuum (SP-BICs) in a 1D silicon grating fabricated on a lithium niobate substrate is presented. bBoth transverse electric and magnetic polarization states are investigated, leading to the excitation of four quasi- Bound states In the Continuum (quasi-BIC) resonances, exhibiting distinct behaviors. Under standard illumination conditions (plane of incidence perpendicular to the 1D grating lines), two of these resonances are highly sensitive to illumination conditions, while the other two resonances involving unconventional illumination directions (plane of incidence parallel to the grating lines) are more robust to the angle of incidence, but just as sensitive to external stresses in terms of resonance wavelength and quality factor. Additionally, temperature detection is experimentally demonstrated with a Sensitivity of S_T = 0.81∼nm °C⁻¹, a state-of-the-art value achieved due to significant electromagnetic field enhancement inside the lithium niobate substrate at the quasi-BIC resonance. These findings pave the way for their use in various sensing applications (such as biology, electromagnetic, and temperature sensing), as well as nonlinear applications like second harmonic generation, and electro- and acousto-optic modulation.