• • EFISH enables SHG in centrosymmetric materials by breaking inversion symmetry with an external electric field, achieving effective χ(2) values comparable to traditional nonlinear crystals (e.g., LiNbO3 with χ(2) ~30–70 pm/V), thus expanding the material palette for nonlinear optics to include CMOS-compatible platforms like Si and Si3N4.
• • The effect is distinct from current-induced SHG and the quantum-confined Stark effect, offering a purely field-driven mechanism that allows dynamic electrical tuning of nonlinear optical processes without requiring charge injection, which is critical for low-power, high-speed modulators.
• • Material platforms for EFISH span bulk semiconductors, ferroelectrics, van der Waals materials, and polymers, each with unique trade-offs: ferroelectrics provide large internal fields but suffer from hysteresis, while vdW materials offer atomic-scale thickness control for integration into nanophotonic circuits.
• • Applications of EFISH include tunable photonic devices, carrier dynamics probing, and nonlinear modulation across optical, electronic, and THz regimes, with potential for electrically controlled nonlinear metasurfaces that could achieve modulation speeds exceeding 100 GHz, far beyond the ~10 GHz limit of thermal-optic or free-carrier dispersion effects.