摘要
A novel ferroelastic domain reconfiguration mechanism delivers giant thermo-optic response in sol–gel barium titanate (BTO) thin films. • 750 °C-annealed BTO achieves record thermo-optic coefficient of 9.69×10⁻⁴ °C⁻¹, multiple times higher than silicon. • Fully reversible a-c domain switching is realized within the practical 25 °C-100 °C working window for on-chip photonic devices. • Prototype Fabry-Pérot modulator reaches 40% modulation depth for photonic integrated circuits and wavelength selective switching. • The domain engineering strategy is potentially extendable to CMOS-compatible ferroelectric perovskites. Thermo-optic tuning in ferroelectric perovskites has emerged as a promising strategy for achieving broadband, energy-efficient optical modulation. Nevertheless, the physical origins governing the near-room-temperature thermo-optic response of ferroelectrics are still not clearly defined. In this work, we report a previously unexplored thermo-optic mechanism in sol-gel-processed (001)-oriented BaTiO₃ films. This mechanism is driven by thermally induced, reversible a-c ferroelastic domain switching, activated through the synergistic control of interfacial screening, domain, and defect engineering, resulting in a large change in refractive index in the 25°C-100 °C temperature range. Films crystallized at 750 °C exhibit high tetragonal phase purity, strong c-axis alignment, and an exceptional thermo-optic coefficient of 9.69×10 -4 °C⁻¹—over several times larger than that of crystalline silicon—together with reversible domain evolution upon thermal cycling. A Fabry-Pérot thermo-optic modulator incorporating this film delivers 40% intensity modulation in the C-band. These findings establish a ferroelastic-domain-driven route to thermo-optic enhancement in ferroelectric perovskites and lay the groundwork for scalable. Download: Download high-res image (175KB) Download: Download full-size image Fig. X: TOC Graphic.
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