Tantalum Pentoxide Integrated Photonics II: A Promising Photonic Platform for Third-Order Nonlinearities

Third-order nonlinear optical phenomena, particularly stimulated Brillouin scattering (SBS) and Kerr nonlinearity, lay the foundation for various advanced nonlinear applications. Integrating these effects within a low-loss, thermorefractive-stable, and CMOS-compatible photonic platform enables multifunctional and versatile nonlinear photonic integrated circuits. Here, we demonstrate the first backward SBS in tantalum pentoxide (Ta2O5) waveguides, revealing a Brillouin gain of 4.9−1.8+2.3 m–1 W–1 at a Brillouin frequency shift of 11.23 GHz. The strong nonlinear refractive index of 7.8−2.4+3.5×10–19 m2/W supports efficient supercontinuum generation (SCG) and four-wave mixing (FWM) in dispersion-engineered strip and rib waveguides across both anomalous and normal dispersion regimes. In the anomalous dispersion regime, SCG exceeding 300 nm is realized and theoretically extendable to over 1100 nm. FWM experiments exhibit a conversion efficiency of −48.1 dB and a potential bandwidth of 120 nm. In the normal dispersion regime, a flat supercontinuum spanning over 180 nm with power fluctuations below 15 dB is generated, serving as a broadband source for acetylene gas spectroscopy. Ta2O5 outperforms other platforms such as silicon, silicon nitride, and lithium niobate in terms of Kerr nonlinearity, SBS gain, and thermorefractive stability, with a figure of merit of 1.7 × 10–12 m·K·W–2, highlighting its exceptional versatility for multifunctional integrated nonlinear photonics.