Application of Silicon-Based Optoelectronics in Communication

Silicon-based optoelectronics technology explores the novel working principles of micro-nano-scale photons, electronics, and optoelectronic devices in different material systems, and uses technologies and methods compatible with silicon-based integrated circuit processes to integrate them heterogeneously on the same silicon substrate On the surface, a completely new large-scale optoelectronic integrated chip with comprehensive functions is formed. The development of silicon-based optoelectronics began in the 1980s. Soref discovered the plasmonic dispersion effect in crystalline silicon, which provided a theoretical basis for silicon-based electro-optic modulation. Silicon-based optoelectronic technology has the advantages of extremely high bandwidth, ultra-fast rate, and high anti-interference characteristics of light, as well as the advantages of microelectronic technology in large-scale integration, low energy consumption, and low cost, and is more suitable for future high-speed and complex optical communication systems. Intel predicts that the expected cost of silicon-based optical modules in the future can be reduced to $0.3 (/ Gbit s−1 ), which is more cost-effective than InP materials.

The huge potential and commercial value of silicon-based optoelectronics are gradually recognized by the industry. Representative companies mainly include Luxtera, Rockly, Intel, Acacia, Sicoya, etc. The participation of commercial companies has vigorously promoted the development of the industrialization of silicon-based optoelectronics technology.

Rockly was one of the early companies working on the commercialization of silicon-based optoelectronics. Rockly’s silicon-based optoelectronic chip adopts the technical route of 3 μm thick silicon to give full play to the advantages of silicon materials in passive devices. Compared with the general 220 nm thin silicon technical route, Rockly reduces the loss of silicon waveguides by an order of magnitude ( about 0.2 dB/cm); and the 3 μm thick silicon waveguide size is similar to the InP laser mode spot size, which is convenient for hybrid integration with InP lasers and avoids the disadvantages of silicon materials in luminescence; but its disadvantage is that it cannot pass through the doped To design and form a modulator, it is necessary to integrate the InP electroabsorption modulator into a silicon-based optoelectronic chip by means of flip-chip bonding (FCB) to realize the modulation function.

Luxtera (later acquired by Cisco) was also an early company engaged in the research of silicon-based optoelectronic communication chips. Luxtera’s silicon-based optoelectronic chips use grating couplers as input/output (I/O) ports, which can directly connect silicon-based optoelectronic chips without going through splits. Carry out wafer-level testing and packaging, saving overall cost. At the same time, Luxtera’s silicon-based optoelectronic chip packaging technology is also relatively advanced. By going to FCB, laser chips and application-specific integrated circuit (ASIC) chips are mixed and mounted on the surface of silicon-based optoelectronic chips to form a complete silicon-based optoelectronic receiving/transmitting chip engine. , reducing the difficulty of back-end optical module packaging.

Intel released the first 50 Gbit/s optical transmit and receive modules based on silicon-based optoelectronics in 2016. Intel’s silicon-based optoelectronic chip adopts a special evanescent wave coupling structure. Using its own process capabilities, the silicon-based optoelectronic waveguide and the InP chip together form a laser resonator (the working wavelength can be changed by adjusting the structure of the silicon-based optoelectronic waveguide, and at the same time The alignment problem of the optical mode field is avoided), and the overall packaging cost is greatly reduced. The 100G QSFP28 PSM4 silicon-based optoelectronic transceiver module launched by Intel in 2018 is also one of the most successful products in the field of silicon-based optoelectronic communication applications in recent years, with a cumulative shipment of more than 3 million units. Acacia is in a leading position in the long-distance application of silicon-based optoelectronics. It is the first company to launch 100 Gbit/s coherent silicon-based optoelectronic transceiver modules. It has coherent digital signal processing (digital signal processing, DSP) chip design capabilities and industry-leading silicon Based optoelectronic monolithic integration and packaging process. The AC1200 module released in 2018 is the first silicon-based optoelectronic module to achieve 6600 km ultra-long-distance 400 Gbit/s rate signal transmission.

Silicon-based optoelectronic modules for Gbit/s rate signal transmission. Sicoya is a silicon-based optoelectronic chip company that adopts a monolithic integration route. It uses the germanium-silicon bipolar complementary metal oxide semiconductor (GeSi BiCMOS) process developed by IHP to integrate microelectronic integrated circuits (such as drivers, transimpedance amplifiers (TIA) ), etc.) and silicon-based optoelectronic chips are integrated on the same silicon chip, which improves the overall performance. On the one hand, the transmission distance of the high-frequency signal between the driver and the modulator is greatly shortened, and the power consumption of the transmitting end is reduced; on the other hand, due to the shortened signal path between the photodetector and the amplifier, the receiving end has a higher SNR.

The silicon-based optoelectronics industry is developing very rapidly, with continuous breakthroughs in basic research, the successive formation of technical standards, continuous improvement of the industrial chain, and increasingly perfect product solutions. Part of the basic research on silicon-based optoelectronic technology is close to the world-class level, and some key products have achieved industrial breakthroughs based on independent research and development.

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