Integrated silicon carbide modulator for CMOS photonics

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/mm 2 ), 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.