Abstract
Heterogeneous integration of materials with a negative thermo-optic coefficient is a simple and efficient way to compensate the strong detrimental thermal dependence of silicon-on-insulator devices. Yet, the list of materials that are both amenable for photonics fabrication and exhibit a negative TOC is very short and often requires sacrificing loss performance. In this work, we demonstrate that As20S80 chalcogenide glass thin-films can be used to compensate silicon thermal effects in microring resonators while retaining excellent loss figures. We present an experimental characterization of the glass thin-film and of fabricated hybrid microring resonators at telecommunication wavelengths. Nearly athermal operation is demonstrated for the TM polarization with an absolute minimum measured resonance shift of 5.25 pm K−1, corresponding to a waveguide effective index thermal dependence of 4.28×10-6 RIU/K. We show that the thermal dependence can be controlled by changing the cladding thickness and a negative thermal dependence is obtained for the TM polarization. All configurations exhibit unprecedented low loss figures with a maximum measured intrinsic quality factor exceeding 3.9 × 105, corresponding to waveguide propagation loss of 1.37 dB cm−1. A value of−4.75(75)×10-5 RIU/K is measured for the thermo-optic coefficient of As20S80 thin-films.
Highlights
The functionalities of silicon-on-insulator (SOI) can be greatly extended via the heterogeneous integration of advanced materials with complimentary properties and strengths
While multiple reports and demonstrations of athermal operation already exists in the literature [1,2,3,4,5,6,7,8,9,10], most of the research done on athermal silicon photonics is focused on waveguide design and their applications but rely on a handful of select materials that combine a negative thermo-optic coefficient (TOC) with interesting properties for heterogeneous integration, namely, some polymer composition or TiO2
Following the passive measurements presented in the last few paragraphs, the thermal dependence of the hybrid microring resonators (MR) was studied by varying the thermoelectric cooler (TEC) set temperature from 20 °C to 35 °C in steps of 3 °C and acquiring the transmittance using the same laser swept measurement previously the wavelength shift per degree dλr/dT ≈ ∆λr/∆T
Summary
The functionalities of silicon-on-insulator (SOI) can be greatly extended via the heterogeneous integration of advanced materials with complimentary properties and strengths. = 1.8×10−4 K−1) leading to unwanted thermal drift in wavelength selective components such as filters or resonators In this case, cladding the silicon waveguides with a material that has a negative TOC can compensate the refractive index shift of silicon and lead to a reduced or even null thermally induced effective index shift. While multiple reports and demonstrations of athermal operation already exists in the literature [1,2,3,4,5,6,7,8,9,10], most of the research done on athermal silicon photonics is focused on waveguide design and their applications but rely on a handful of select materials that combine a negative TOC with interesting properties for heterogeneous integration, namely, some polymer composition or TiO2. As-S glasses have the rare property of being photosensitive in the near-infrared, allowing to use light for modification of the refractive index of the glass for resonance trimming or Bragg grating inscription [7,14,15,16]
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