photonic integrated circuit

**Photonic Integrated Circuits (PICs)** — chips that manipulate light instead of electrons, enabling high-bandwidth, low-power data communication and sensing by integrating optical components on semiconductor substrates. **Why Photonics?** - Electrical wires: Bandwidth limited by RC delay, power grows with distance and data rate - Optical: Speed of light, no RC delay, bandwidth independent of distance - At >100 Gbps per lane, optics becomes more efficient than copper **Key Components on a PIC** - **Waveguide**: Guides light on-chip (analogous to a wire for electrons) - **Modulator**: Converts electrical signal to optical signal (E/O) - **Photodetector**: Converts optical back to electrical (O/E) - **Multiplexer/Demultiplexer**: Combine/split multiple wavelengths (WDM) - **Coupler/Splitter**: Combine or divide optical power **Silicon Photonics** - Use standard CMOS fabs to build optical components in silicon - Silicon is transparent at telecom wavelengths (1310/1550 nm) - Co-package with electronics for minimum latency - Providers: Intel, Cisco (Acacia), Broadcom, GlobalFoundries **Applications** - Data center interconnects (400G, 800G, 1.6T Ethernet) - AI cluster networking (GPU-to-GPU communication) - LiDAR for autonomous vehicles - Biosensors and medical diagnostics **Photonics** is transitioning from fiber optics into the chip — it's the technology that will enable the next order-of-magnitude increase in data center bandwidth.