Abstract
We report on the design and measurement of tellurium oxide microcavity resonators coupled to silicon bus waveguides on silicon photonic chips. The resonators are fabricated using a standard silicon photonics foundry processing flow in which the SiO2 top-cladding is etched in a ring shape and aligned next to a silicon bus waveguide. The resulting microtrench is coated in a tellurium oxide film by reactive sputtering in a post-processing step to form the waveguiding layer of the resonator. A 100-μm radius trench with a 1115-nm-thick TeO2 film is measured to have an internal Q factor of 0.9 × 105. Smoothing the etch wall surface with a fluoropolymer coating is shown to enhance the Q factor of several devices, with a trench coated in a 630-nm-thick TeO2 film demonstrating a Q factor of 2.1 × 105 corresponding to 1.7-dB/cm waveguide loss. These results demonstrate a potential pathway toward monolithic integration of tellurite glass-based nonlinear and rare-earth-doped devices compatible with silicon photonics platforms.
Highlights
IntroductionIntegrated photonic circuits based in silicon-on-insulator (SOI) waveguides are a leading photonics platform due to their mature complementary metal-oxide-semiconductor (CMOS) compatible fabrication technology that can leverage the existing silicon electronics fabrication infrastructure.[1,2] A large library of established passive silicon photonic components, such as fiber-chip couplers, wavelength-division-multiplexors, and filters are well developed, as well as opto-electronic devices, such as modulators and photodetectors.[2,3,4] challenges still exist in fabricating light sources with silicon waveguides, including optically pumped nonlinear and rare-earth-doped active photonic devices, due to silicon’s large two-photon absorption at telecommunications wavelengths[5,6] and low rare earth solubility,[7,8] respectively
We have demonstrated integrated TeO2 microtrench resonators on silicon photonic chips using a standard wafer-scale foundry process and a straightforward low-temperature post-processing TeO2 deposition step
Calculations show that even with TeO2 coating thicknesses of over 1000 nm, the microcavities can reasonably be bent below a 40-μm radius, which maintains a compact footprint on scale with silicon photonic devices
Summary
Integrated photonic circuits based in silicon-on-insulator (SOI) waveguides are a leading photonics platform due to their mature complementary metal-oxide-semiconductor (CMOS) compatible fabrication technology that can leverage the existing silicon electronics fabrication infrastructure.[1,2] A large library of established passive silicon photonic components, such as fiber-chip couplers, wavelength-division-multiplexors, and filters are well developed, as well as opto-electronic devices, such as modulators and photodetectors.[2,3,4] challenges still exist in fabricating light sources with silicon waveguides, including optically pumped nonlinear and rare-earth-doped active photonic devices, due to silicon’s large two-photon absorption at telecommunications wavelengths[5,6] and low rare earth solubility,[7,8] respectively. We have previously shown applications of this platform toward thermal and evanescent waveguide sensor devices.[44] Here, we provide greater detail on the cavity design and device properties, as well as improved device performance, showing Q factors of up to 2.1 × 105 by using polymer coatings to smooth the microtrench sidewall These results demonstrate a platform for future integration of nonlinear photonic and rare-earth-doped active tellurite resonators on a silicon photonics platform, for applications including Kerr comb sources for sensing and spectroscopy,[45] laser biosensors for diagnostic systems on a chip,[46] and high-power light sources for communications and detection and ranging.[47]
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