Low-loss low thermo-optic coefficient Ta2O5on crystal quartz planar optical waveguides

Qiancheng Zhao, Ryan O. Behunin, Peter T. Rakich, Nitesh Chauhan, Andrei Isichenko, Jiawei Wang, Chad Hoyt, Chad Fertig, Mu Hong Lin, Daniel J. Blumenthal

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


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.

Original languageEnglish (US)
Article number116103
JournalAPL Photonics
Issue number11
StatePublished - Nov 1 2020

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Computer Networks and Communications


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