Graham T. Reed

The explosive growth of artificial intelligence (AI) and high‑performance computing (HPC) workloads is placing increasingly stringent demands on optical interconnects for fast, reliable, and mass‑manufacturable photonic receivers 1–3. Germanium (Ge)-on-silicon (Si) photodetectors have demonstrated impressive bandwidth and responsivity, yet large-signal operation beyond 400 Gbps per wavelength has remained largely inaccessible in foundry-compatible platforms 4–6. Here we show that a mass-manufacturable 300 mm monolithic complementary metal-oxide-semiconductor (CMOS) silicon photonics (SiPh) platform can overcome this limitation. An O‑band Ge‑on‑Si lateral photodetector achieves large‑signal data rates exceeding 448 Gbps per wavelength with four‑level pulse‑amplitude modulation (PAM4) and 520 Gbps with six‑level pulse‑amplitude modulation (PAM6) at a photocurrent of ~2 mA. This performance is enabled by an optoelectronic bandwidth of up to ~215 GHz, near‑unity quantum efficiency, and a record bandwidth-responsivity product exceeding ~217 GHz·A W⁻¹ - more than 2 times higher than the previous best of 108 GHz·A W⁻¹ for waveguide‑coupled Ge photodiodes - while sustaining optical input powers up to 2.8 mW and maintaining sub‑38 nA dark current at -1 V bias. Crucially, these metrics are attained without inductive peaking, avalanche gain, or transimpedance-amplifier (TIA) integration, with uniform high-speed characteristics across a full 300 mm wafer, underscoring production-level reproducibility. The same platform supports high speed depletion mode, travelling wave Si Mach-Zehnder modulators (MZMs) capable of ≥400 Gbps per wavelength operation without digital signal processing (DSP), precision silicon nitride (SiN) wavelength division multiplexing (WDM) filters with sub 1.5 nanometre channel stability, low loss detachable fibre-chip input-output (I/O) (~1 dB per facet), co integrated CMOS circuits using ≥350 GHz class ft transistors, and advanced wafer level packaging features. To the best of our knowledge, this is the first monolithic CMOS silicon photonics foundry platform uniting ≥400 Gbps-class transmitter and receiver functions on a single substrate, providing a scalable foundation for next-generation pluggable, near- and co-packaged (NPO/CPO) optical interconnects in AI/HPC systems.

Methods for high resolution phase trimming of silicon Mach–Zehnder interferometers via the electrical annealing of amorphized waveguide sections are presented. A high resolution of phase change is necessary to accurately trim the performance of individual devices to correct fabrication errors and when scaling to large programmable photonic circuits. On‐chip microheaters positioned above amorphous waveguide sections are driven by short voltage pulses, causing a degree of recrystallization, controllably changing the material's refractive index. An average resolution of phase change per voltage pulse of 0.0007π is demonstrated if an adaptive method is employed, where the voltage step between successive pulses is set to be dependent on the average phase change brought about by the previous three voltage pulses.

The increasing demand for energy-efficient hardware for artificial intelligence (AI) and data centres requires integrated photonic solutions delivering optical transceivers with Tbit/s data rates and energy consumption2, achieving a dynamic power consumption∼58fJ/bit, ∼3 times lower than previous graphene modulators and Mach-Zehnder modulators based on Si or lithium niobate. We show devices with∼0.037dB/Vμm modulation efficiency,∼16 times better than previous demonstrations based on graphene. This paves the way to wafer-scale production of graphene modulators on Si useful for Tbit/s optical transceivers and energy-efficient AI.

Lead (Pb²⁺) toxification is a concerning, unaddressed global public health crisis that leads to 1 million deaths annually. Yet, public policies to address this issue have fallen short. This work harnesses the unique abilities of crown ethers, which selectively bind to specific ions. This study demonstrates the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion. This realizes an integrated photonic platform that enables the in-operando, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, facilitating the subsequent amine conjugation for various crown ethers. The presented platform is specifically engineered for selective Pb²⁺ detection, demonstrating a large dynamic detection range, and applicability to field samples. The compatibility of this platform with cost-effective manufacturing indicates the potential for pervasive implementation of the integrated photonic sensor technology to safeguard against societal Pb²⁺ poisoning.

Lead (Pb²⁺) toxification in society is one of the most concerning public health crises that remains unaddressed. The exposure to Pb²⁺ poisoning leads to a multitude of enduring health issues, even at the part-per-billion scale (ppb). Yet, public action dwarfs its impact. Pb²⁺ poisoning is estimated to account for 1 millions deaths per year globally, which is in addition to its chronic impact on children. With their ring-shaped cavities, crown ethers are uniquely capable of selectively binding to specific ions. In this work, for the first time, the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion is demonstrated. This realizes a photonic platform that enables the in-situ, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, laying the ground for subsequent amine conjugation for various crown ethers. In this work, the platform is engineered for Pb²⁺ detection, demonstrating a large dynamic detection range of 1–262000 ppb with high selectivity against a wide range of relevant ions. These results indicate the potential for the pervasive implementation of the technology to safeguard against ubiquitous lead poisoning in our society.

The widening application of advanced digital infrastructure requires the development of communications technologies with increased data transmission rates. However, ensuring that this can be achieved in an energy-efficient way is challenging. Here we report an integrated complementary metal–oxide–semiconductor/silicon-photonics-based transmitter in which a switching current is applied to the passive-equalization-network-guided silicon Mach–Zehnder modulator, rather than driving a standard Mach–Zehnder modulator with a traditional voltage swing. This approach allows the total electrical energy to be selectively distributed to different frequency components by choosing an appropriate inductance and near-end termination impedance values. With the approach, we achieve 112 gigabaud—112 gigabits per second on–off keying and 224 gigabit per second pulse-amplitude modulation with four levels—transmission with energy efficiencies below picojoules per bit, and without the need for signal-shaping functions in the data source. We also investigate the bit error rate for different electrical and optical power conditions at 100 gigabaud, including the electrical power consumption of the driver amplifier.

We report the design, fabrication, and characterization of a universal silicon p-n junction ring resonator for C band error-free communication links operated up to 50 Gb/s with co-designed optical modulation and detection performance. The universal p-n junction ring device shows co-designed detection responsivity up to 0.84 A/W, and in conjunction with a modulation efficiency of ~4 Vmm and >8 dB optical modulation extinction ratio (ER), enabling C band 50-Gb/s NRZ communication link with bit error rate (BER) ≤ 3×10^-12. Individually, the speed of modulation and detection is measured up to 112 Gb/s and 80 Gb/s, respectively. The principle of co-designing PN junction ring modulator and detector performance required for error-free communication links can significantly ease the fabrication yield challenges of ring structures by reducing the number of types of devices. The principle can also be applied to O band wavelengths. To the best of our knowledge, for the first time, a device of this type has achieved both error-free modulation and detection operation up to 50 Gb/s in the C band individually or in conjugation as an error free communication link, which paves the way to realize a >1.6 Tb/s all-silicon WDM based error free optical transceiver link in future and is essential for future programmable photonics circuits.

The escalating need for expansive data bandwidth, and the resulting capacity constraints of the single mode fiber (SMF) have positioned the 2-μm waveband as a prospective window for emerging applications in optical communication. This has initiated an ecosystem of silicon photonic components in the region driven by CMOS compatibility, low cost, high efficiency and potential for large-scale integration. In this study, we demonstrate a plasma dispersive 4 × 4 photonic switch operating at the 2-μm waveband with the highest switching speed. The demonstrated switch operates across a 45-nm bandwidth, with 10-90% rise and 90-10% fall time of 1.78 ns and 3.02 ns respectively. In a 4 × 4 implementation, crosstalk below -15 dB and power consumption lower than 19.15 mW across all 16 optical paths are indicated. This result brings high-speed optical switching to the portfolio of devices at the promising waveband.

This conference presentation was prepared for Photonics West, 2023,