Owing to its attractive optical and electronic properties, silicon carbide is an emerging platform for integrated photonics. However an integral component of the platform is missing—an electro-optic modulator, a device which encodes electrical signals onto light. As a non-centrosymmetric crystal, silicon carbide exhibits the Pockels effect, yet a modulator has not been realized since the discovery of this effect more than three decades ago. Here we design, fabricate, and demonstrate a Pockels modulator in silicon carbide. Specifically, we realize a waveguide-integrated, small form-factor, gigahertz-bandwidth modulator that operates using complementary metal-oxide-semiconductor (CMOS)-level voltages on a thin film of silicon carbide on insulator. Our device is fabricated using a CMOS foundry compatible fabrication process and features no signal degradation, no presence of photorefractive effects, and stable operation at high optical intensities (913 kW/mm2), allowing for high optical signal-to-noise ratios for modern communications. Our work unites Pockels electro-optics with a CMOS foundry compatible platform in silicon carbide.

Herein, the impact and spin‐coating process of Nafion thin films on photonic nanowaveguide structures fabricated via a complementary metal–oxide–semiconductor compatible process for the first time is investigated. Particularly, the effect of Nafion thin films (≈23–776 nm) on microring resonators (MRRs) with compact waveguide sizes (480 nm by 220 nm and 380 nm by 220 nm) is focused on, where the microring provides enhanced interactions between the Nafion and light, which is related to Nafion thin‐film properties such as the refractive index, water uptake, and swelling. The results demonstrate small, compact, and cost‐effective MRR devices to characterize Nafion thin film and high‐resolution on‐chip humidity sensing for real‐time and continuous measurements.

The electro-optic modulator encodes electrical signals onto an optical carrier, and is essential for the operation of global communication systems and data centers that society demands. An ideal modulator results from scalable semiconductor fabrication and is integrable with electronics. Accordingly, it is compatible with complementary metal-oxide-semiconductor (CMOS) fabrication processes. Moreover, modulators using the Pockels effect enables low loss, ultrafast, and wide-bandwidth data transmission. Although strained silicon-based modulators could satisfy these criteria, fundamental limitations such as two-photon absorption, poor thermal stability and a narrow transparency window hinder their performance. On the other hand, as a wide bandgap semiconductor material, silicon carbide is CMOS compatible and does not suffer from these limitations. Due to its combination of color centers, high breakdown voltage, and strong thermal conductivity, silicon carbide is a promising material for CMOS electronics and photonics with applications ranging from sensors to quantum and nonlinear photonics. Importantly, silicon carbide exhibits the Pockels effect, but a modulator has not been realized since the discovery of this effect more than three decades ago. Here we design, fabricate, and demonstrate the first Pockels modulator in silicon carbide. Specifically, we realize a waveguide-integrated, small form-factor, gigahertz-bandwidth modulator that can operate using CMOS-level drive voltages on a thin film of silicon carbide on insulator. Furthermore, the device features no signal degradation and stable operation at high optical intensities (913 kW/mm2), allowing for high optical signal-to-noise ratios for long distance communications. Our work unites Pockels electro-optics with a CMOS platform to pave the way for foundry-compatible integrated photonics.

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We measure the photothermal nonlinear response in suspended cubic silicon carbide (3C-SiC) and 3C-SiC-on-insulator (SiCOI) microring resonators. Bi-stability and thermo-optic hysteresis is observed in both types of resonators, with the suspended resonators showing a stronger response. A photothermal nonlinear index of 4.02×10−15 m2/W is determined for the suspended resonators, while the SiCOI resonators demonstrate one order of magnitude lower photothermal nonlinear index of 4.32×10−16 m2/W. Cavity absorption and temperature analysis suggest that the differences in thermal bi-stability are due to variations in waveguide absorption, likely from crystal defect density differences throughout the epitaxially grown layers. Furthermore, coupled mode theory model shows that the strength of the optical bi-stability, in suspended and SiCOI resonators can be engineered for high power or nonlinear applications.