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Ultra-low-loss Ta2O5-core/SiO2-clad planar waveguides on Si substrates


An increasing number of systems and applications depend on photonics for transmission and signal processing. This includes data centers, communications systems, environmental sensing, radar, lidar, and microwave signal generation. Such systems increasingly rely on monolithic integration of traditionally bulk optical components onto the chip scale to significantly reduce power and cost while simultaneously maintaining the requisite performance specifications at high production volumes. A critical aspect to meeting these challenges is the loss of the waveguide on the integrated optic platform, along with the capability of designing a wide range of passive and active optical elements while providing compatibility with low-cost, highly manufacturable processes, such as those found in CMOS. In this article, we report the demonstration of a record low propagation loss of 3 ± 1 dB∕m across the entire telecommunications C-band for a CMOS-compatible Ta2O5-core∕SiO2-clad planar waveguide. The waveguide design, fabrication process, and optical frequency domain reflectometry characterization of the waveguide propagation loss and group index are described in detail. The losses and dispersion properties of this platform enable the integration of a wide variety of linear and nonlinear optical components on-chip, as well as integration with active rare-earth components for lasers and amplifiers and additionally silicon photonic integrated devices. This opens up new integration possibilities within the data communications, microwave photonics, high bandwidth electrical RF systems, sensing, and optical signal processing applications and research communities.

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