Ultra-high Q-factor quasi-BIC BaTiO₃ metasurface for electro-optic modulation

Area of Science:

• Metasurfaces
• Optoelectronics
• Nanophotonics

Background:

• Metasurfaces enhance light-matter interactions by trapping specific wavelengths.
• Electro-optic modulation metasurfaces offer fast, stable, and efficient dynamic modulation.
• High Q-factor resonances are crucial for detecting weak electro-optic effects.

Purpose of the Study:

• To design an electro-optic modulation metasurface that facilitates voltage application and achieves near 100% modulation efficiency.
• To leverage quasi-bound states in the continuum (Q-BIC) for enhanced modulation sensitivity.
• To provide a theoretical basis for efficient, dynamic metasurface design.

Main Methods:

• Finite-difference time-domain (FDTD) method used for modeling single-crystal BTO metasurfaces.
• Structural symmetry was broken to introduce Q-BIC resonance.
• Simulated applied electric field to induce refractive index changes.

Main Results:

• Achieved a high Q-factor optical signal of 2.45 × 10⁴.
• A refractive index change of 8 × 10^-4 in BTO resulted in 100% electro-optical intensity modulation depth under a 143 V/mm electric field.
• The metasurface nanostructure is designed for facile nano-fabrication and voltage application.

Conclusions:

• The simulated BTO metasurface demonstrates the potential for high-depth electro-optic modulation.
• The design is suitable for low-power, CMOS-compatible, and miniaturized electro-optic devices.
• Provides crucial theoretical guidance for realizing efficient dynamic metasurfaces.