Optical resonator-based frequency stabilization plays a critical role in ultra-low linewidth laser emission and precision sensing, atom clocks, and quantum applications. However, there has been limited success in translating traditional bench-top stabilization cavities to compact on-chip integrated waveguide structures that are compatible with photonic integration. The challenge lies in realizing waveguides that not only deliver low optical loss but also exhibit a low thermo-optic coefficient and frequency noise stability. Given the problematic sources of frequency noise within dielectrics, such as thermorefractive noise, resonators with small thermo-optic response are desirable for on-chip reference cavities. We report the first demonstration of a Ta₂O₅ (tantala) waveguide core fabricated on a crystal quartz substrate lower cladding with TEOS-PECVD SiO₂ upper cladding. This waveguide offers significant advantages over other waveguides in terms of its low thermo-optic coefficient and reduced thermorefractive-related frequency noise. We describe the waveguide structure and key design parameters as well as fabrication considerations for processing tantala on quartz waveguides. We report a waveguide thermo-optic coefficient of −1.14 × 10⁻⁶ RIU/K, a value that is over 6 times smaller in magnitude than that of SiO₂-substrate tantala waveguides, with a propagation loss of 1.19 dB/cm at 1550 nm and <1.33 dB/cm across the 1525 nm–1610 nm wavelength range. Within a 1.6 mm radius ring resonator, we demonstrate a 2.54 × 10⁵ intrinsic Q factor. With the potential for very low loss and the ability to control the thermal response, this waveguide platform takes a key step toward creating thermally stable integrated resonators for on-chip laser frequency stabilization and other applications.

中文翻译：

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晶体石英平面光波导上的低损耗低热光系数Ta2O5

基于光学谐振器的频率稳定在超低线宽激光发射和精确感测，原子钟以及量子应用中起着至关重要的作用。然而，在将传统的台式稳定腔转换成与光子集成兼容的紧凑的片上集成波导结构方面，成功的有限。挑战在于实现不仅具有低光学损耗而且还具有低热光系数和频率噪声稳定性的波导。考虑到电介质中频率噪声的问题源，例如热折射噪声，对于片上基准腔，希望具有小的热光响应的谐振器。我们报告了Ta ₂ O ₅的首次演示（tantala）波导芯制造在带有TEOS-PECVD SiO ₂上包层的石英晶体衬底下包层上。就其低的热光系数和减少的热折射相关的频率噪声而言，该波导比其他波导具有明显的优势。我们描述了波导结构和关键设计参数，以及在石英波导上处理塔塔拉的制造注意事项。我们报告的波导热光系数为-1.14×10 ^-6 RIU / K，该值的大小比SiO ₂小6倍以上基板塔塔拉波导管，在1550 nm处的传播损耗为1.19 dB / cm，在1525 nm至1610 nm的波长范围内的传输损耗为<1.33 dB / cm。在半径为1.6 mm的环形谐振器内，我们证明了2.54×10 ^5的固有Q因子。由于具有极低的损耗潜力和控制热响应的能力，该波导平台迈出了关键一步，以创建用于片上激光频率稳定化和其他应用的热稳定集成谐振器。