Ultra-low-loss Ta2O5 waveguide for integrated nonlinear photonics

Abstract

Integrated nonlinear photonics demands waveguides that simultaneously offer ultra-low-loss, relatively strong nonlinearity, and tight mode confinement. Tantalum pentoxide (Ta2O5) is attractive for this purpose because it combines a broad transparency window, relatively strong third-order nonlinearity, and favorable thick-film growth characteristics. In tightly confined Ta2O5 waveguides, however, enhanced interaction between the optical mode and etched sidewalls makes scattering loss an important limitation for achieving high Q anomalous-dispersion resonators. Here, we mitigate this confinement-scattering trade-off in pure Ta2O5 waveguides using a fabrication flow based on the Damascene concept. The resulting microring resonators (MRRs) with a cross-section of 1.6 μm x 0.85 μm exhibit intrinsic quality factors exceeding 4.0 x 106, corresponding to propagation losses below 10 dB/m, while maintaining anomalous dispersion suitable for bright dissipative Kerr soliton operation. Using these resonators, we generate a coherent bright single-soliton microcomb with a repetition rate of 108.32 GHz. Under optimized dual-pump operating conditions, the platform further exhibits an experimentally accessible single-soliton window spanning 7.5 GHz, indicating a large detuning tolerance for soliton operation; this broad operating window is consistent with the relatively weak thermo-optic response of Ta2O5. Thermal-bistability analysis further indicates that the residual scattering loss is comparable to the material-absorption loss, rather than dominating the loss budget. These results demonstrate that low optical loss, tight mode confinement, and dispersion engineering suitable for soliton formation can be jointly achieved in a pure Ta2O5 platform, providing an ultra-low-loss platform foundation for integrated nonlinear photonic devices and more complex chip-scale nonlinear photonic systems.

9 pages, 4 figures, 1 table. Accepted for publication in Optica

References in corpus (16)

• All-optical signal processing platforms for CMOS compatible integrated nonlinear optics
• Photonic Damascene Process for Integrated High-Q Microresonator Based Nonlinear Photonics
• Ultra-efficient frequency comb generation in AlGaAs-on-insulator microresonators
• Stably accessing octave-spanning microresonator frequency combs in the soliton regime
• 422 Million Q Planar Integrated All-Waveguide Resonator with a 3.4 Billion Absorption Limited Q and Sub-MHz Linewidth
• Probing the loss origins of ultra-smooth $\mathrm{S}{\mathrm{i}}_3{\mathrm{N}}_4$ integrated photonic waveguides
• Ultralow-power chip-based soliton microcombs for photonic integration
• III-Nitride nanophotonics for beyond-octave soliton generation and self-referencing
• Tailoring microcombs with inverse-designed, meta-dispersion microresonators
• Ultra-Broadband Kerr Microcomb Through Soliton Spectral Translation
• Probing material absorption and optical nonlinearity of integrated photonic materials
• Anneal-free ultra-low loss silicon nitride integrated photonics
• Ultra-Low-Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries
• Prediction of New Ground State Crystal Structure of Ta2O5
• Toward ultimate-efficiency frequency conversion in nonlinear optical microresonators
• Measurements of Optical Scatter Versus Annealing Temperature for Amorphous Ta2O5 and TiO2:Ta2O5 Thin Films