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

Third-order nonlinear optical phenomena, including Kerr nonlinearity and stimulated Brillouin scattering (SBS), lay the foundation for a variety of nonlinear applications. Harnessing Kerr and SBS effects within a low-loss, thermorefractive-stable, and CMOS-compatible photonic platform will revolutionize nonlinear photonic integrated circuits towards multi-functionality and versatility. In this work, we investigate tantalum pentoxide (Ta ₂ O ₅ ) waveguides and demonstrate their unique potential for supercontinuum generation (SCG) and four-wave mixing (FWM), enabled by a strong Kerr nonlinearity of \(\:{7.83}_{-2.39}^{+3.45}\)×10 ⁻¹⁹ m ² /W. Notably, we report the first demonstration of backward Brillouin scattering in Ta ₂ O ₅ waveguides, with a Brillouin gain of \(\:{4.9}_{-1.8}^{+2.3}\) m ^-1 W ^-1 and a Brillouin frequency shift of 11.23 GHz. These waveguides are designed with rib and strip structures to enable dispersion engineering. In the normal dispersion regime, Ta ₂ O ₅ rib waveguides generate a flat supercontinuum spanning over 180 nm with power fluctuations below 15 dB, serving as a broadband source for acetylene gas spectroscopy. In the anomalous dispersion regime, SCG exceeding 300 nm is realized and theoretically extendable to over 1100 nm. FWM experiments reveal a conversion efficiency of − 48.09 dB and a bandwidth of 120 nm, highlighting the role of dispersion in nonlinear interactions. Our Ta ₂ O ₅ waveguides exhibit a figure of merit (FOM) of 1.7×10 ^-12 m∙K∙W ^-2 , outperforming platforms such as silicon, silicon nitride, and lithium niobate in terms of Kerr nonlinearity, SBS gain, and thermorefractive stability. These findings highlight the exceptional versatility of the Ta ₂ O ₅ platform for multi-functional integrated nonlinear photonics, paving the way towards on-chip ultra-broadband light sources, frequency combs, and advanced signal processing.