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Automotive And Consumer Applications Are Benefitting From Silicon Photonics Technologies


Silicon Photonics (SiP) has benefitted from strong pull by the communications sector. By leveraging the industry’s vast storehouse of CMOS and related high volume Silicon processes, materials and packaging expertise, SiP is growing beyond telecom & datacom to bring the economies and performance of Silicon manufacturing to automotive and biotech applications. BY ERIC HIGHAM, DIRECTOR – ADVANCEDSEMICONDUCTOR APPLICATIONS/ADVANCED DEFENSE APPLICATIONS, STRATEGY ANALYTICS

AS GLOBAL ECONOMIES continue to recover from COVID and the pace of events around the world quickens, the importance of broadband connectivity is clear. Countries are expanding their broadband footprints and users are clamoring for higher data rates to accommodate their growing video and application appetites. The result has been an explosion of data traffic over the past decade. The curves in Figure 1 show an extrapolation of Cisco network data for the next decade and the conclusion is inescapable; data traffic is large and growing quickly.

The red curve shows IP (Internet Protocol) data traffic and this represents any bit of transmitted data, whether that data is on a wireless or wireline network. This data extrapolation predicts traffic to increase by a factor of 125 times over the forecast period. Even more impressive is the magnitude of data shown by the blue line. This curve represents expected data traffic in data centers. This short-reach data traffic runs between five and six times the magnitude of the IP data and it reflects the increasing importance of data communications as we have become more comfortable with the cloud and the home becomes the center of many of our interactions with the world.

The magnitude of this communications activity is becoming clearer. The emerging 5G wireless standard will drive the entire electronics market with cellular terminals exceeding 1 billion units. There are reports of total optical transceiver shipments reaching 1 billion in the next 5 years and yearly data center port shipments exceeding 60 million in the next couple of years.

This communications opportunity, along with the technical requirements have been instrumental in the development and maturation of silicon photonics and the broader photonics integrated circuits (PIC) ecosystem. While communications opportunities currently drive the optical market, the industry is looking at other fast growth, high volume applications that could benefit from more optical content in devices and networks.

Figure 1: Data Traffic Projection

Silicon Photonics

Photonics devices face the same pressures as electronic devices to be smaller and less expensive, with better performance to enable more capabilities. The response to these challenges from optical component manufactures has been more integration. Photonic integrated circuit design and manufacturing techniques have gained traction as the component roadmap evolves to include more electrical and optical functions in an optical module. These modules are a mix of direct and coherent detection schemes and that means a variety of compound semiconductors to optimize the linear functions, along with an increasing amount of digital silicon to increase performance characteristics.

Figure 2: Photonic Integrated Circuit Conceptual Block Diagra. Source: S. Y. Siew, et al, Review of Silicon Photonics Technology and Platform Development, Journal of Lightwave Technology, 2021

Figure 2 shows a conceptual block diagram of the functions that a photonic integrated circuit must address. As digital processing and control capabilities become more important in optical applications, silicon becomes the natural choice for an integration medium. This allows for relatively low volume opportunities to take advantage of the massive processing and manufacturing infrastructure in place for silicon technologies. Manufacturers are using existing silicon CMOS-based processes for all the functions shown in Figure 2, except for the generation function. Silicon is an indirect bandgap material, so it will not emit photons meaning that the generation function requires another technology. The silicon photonics device becomes a subset of a photonics integrated circuit, with a silicon integrated circuit accomplishing all the required functions except for the laser.

New Market Applications
Broadly, the optical industry is becoming extremely excited about the potential in sensing applications. Automotive platforms are generating significant interest as that industry evolves toward more electric vehicles, more sophisticated ADAS (Advanced Driver Assistance Systems) capabilities and full autonomation. After being hard hit by COVID, the automotive industry is trending toward global sales of 100 million vehicles per year and as Figure 3 shows, sensing and detection opportunities in automobiles are increasing and becoming very sophisticated. Vehicle platforms of assorted sizes and purposes are becoming webs of sensor inputs.

The term “sensor” encompasses many distinct functions and technologies. Sensors became increasingly important in automotive applications as vehicles began to incorporate more computerized functions. As semiconductor detection and processing capabilities have improved, the scope of driver assistance has increased. A thorough discussion of the full range of sensor applications and technologies is outside the scope of this discussion, but most vehicles sold today use a combination of cameras, ultrasonic sensors and radar at different frequencies to enable features like adaptive cruise control, parking assistance, automatic emergency braking, and blind spot monitoring. These technologies have advantages and disadvantages and the photonics industry is particularly interested in building on early successes with LiDAR systems to help enable the automotive industry's evolution to full automation.