Just as electronic ICs integrate transistors, a Photonic Integrated Circuit (PIC) integrates optical components — lasers, waveguides, modulators, detectors — onto one chip to manipulate light instead of electrons. Light moves data with vast bandwidth, no resistive heating, and immunity to electromagnetic interference, which is why optics is invading the data centre.
Working principle
Light is confined in waveguides — high-index cores (silicon or silicon nitride) surrounded by lower-index cladding — by total internal reflection. A modulator imprints data onto the optical carrier by changing the waveguide's refractive index (via free-carrier or electro-optic effects), typically inside a Mach–Zehnder interferometer or ring resonator. A photodetector (usually germanium on silicon) converts received light back to current. Silicon photonics builds all of this on standard CMOS foundry lines.
| Property | Copper / electronic | Photonic |
|---|---|---|
| Bandwidth | Limited by RC | Very high (WDM) |
| Loss over distance | High | Very low |
| Crosstalk / EMI | Significant | Negligible |
| Energy / bit | Higher at high rate | Lower |
| Challenge | Signal integrity | Laser integration, coupling |
Industry driverCo-packaged optics — placing PICs beside the switch ASIC — is the near-term driver, slashing the energy needed to move terabits inside AI/data-centre fabrics.
Applications
- Data-centre transceivers and co-packaged optics for AI clusters
- LiDAR and optical sensing on chip
- Quantum photonics and emerging optical neural-network accelerators
References & further reading
- Thomson et al., “Roadmap on silicon photonics,” J. Optics, 2016.
- Sun et al., “Single-chip microprocessor that communicates directly using light,” Nature, 2015.
- Shastri et al., “Photonics for artificial intelligence and neuromorphic computing,” Nature Photonics, 2021.