Silicon Photonic Modulation Techniques for High-Speed Communication

Silicon photonics has emerged as a leading platform for high-speed optical interconnects, harnessing the mature CMOS fabrication infrastructure to achieve compact, scalable and cost-effective modulators. Modulation is predominantly realised through free-carrier effects in silicon—either by injection, depletion or accumulation—which alter refractive index and absorption to encode data onto optical carriers. Interferometric approaches, notably Mach–Zehnder modulators, offer broad bandwidths and linear response, while resonant structures such as microring modulators deliver reduced footprint and lower drive voltages. Recent advances have focussed on energy-per-bit reduction to the femtojoule regime, bitrates exceeding 100 Gb s⁻¹ per channel and integration of multiple wavelengths via dense wavelength division multiplexing. The integration of novel materials, including heterogeneous electro-optic films and two-dimensional semiconductors, promises to transcend intrinsic trade-offs between bandwidth, efficiency and loss, enabling future photonic networks for data centres, high-performance computing and emerging quantum systems.

Research from Nature Portfolio

Recent studies have demonstrated a fully integrated CMOS-compatible silicon photonics transmitter capable of 112 Gbaud on-off keying and 224 Gb s⁻¹ four-level pulse-amplitude modulation, with energy consumption below one picojoule per bit. This is achieved by steering the electrical energy distribution via a passive-equalisation-network-driven Mach–Zehnder modulator, eliminating the need for upstream signal shaping. Bit error rate performance was systematically characterised under varied electrical and optical power configurations, confirming reliable operation at 100 Gbaud. In parallel, a dense wavelength division multiplexing microring resonator array has been realised on a silicon chip, leveraging dual-segment Z-shaped p-n junctions to alleviate the bandwidth–efficiency trade-off. This device delivers an aggregate data rate of 1 Tb s⁻¹ with per-lane throughput of 200 Gb s⁻¹ and energy efficiencies in the sub-10 fJ bit⁻¹ regime, underscoring the scalability of all-silicon modulator architectures for future optical interconnects.

Silicon Photonic Modulation Techniques for High-Speed Communication publication trend

The graph below shows the total number of articles in silicon photonic modulation techniques for high-speed communication across all publications each year (not limited to Nature Index journals).

Technical terms

Plasma dispersion effect: Variation in silicon’s refractive index and absorption induced by changes in free-carrier concentration.

Mach–Zehnder modulator: Interferometric device that encodes data by inducing phase shifts in split optical paths.

Microring resonator: Compact ring-shaped waveguide that filters and modulates light at resonant wavelengths.

Wavelength division multiplexing: Technique combining multiple optical carrier wavelengths to increase aggregate data throughput.

Pulse-amplitude modulation (PAM): Multi-level signalling method encoding information in discrete optical amplitude levels.

References

1. An integrated CMOS–silicon photonics transmitter with a 112 gigabaud transmission and picojoule per bit energy efficiency. Nature Electronics (2023).
2. A 5 × 200 Gbps microring modulator silicon chip empowered by two-segment Z-shape junctions. Nature Communications (2024).
3. 2D material platform for overcoming the amplitude–phase tradeoff in ring resonators. Optica (2024).
4. Taking silicon photonics modulators to a higher performance level: state-of-the-art and a review of new technologies. Advanced Photonics (2021).