Faster, lighter, more durable, and, at the end of the day, also much cheaper: the benefits of photonic circuits are considerable, for a wide range of applications. And the Netherlands plays an important role, globally, in the development and application of this key technology. In recent years, under the leadership of PhotonDelta, a solid foundation has been laid under the Dutch integrated photonics ecosystem. One of the important application areas of this key technology is heterogeneous integration, the combination of different technologies. Read the other parts of the series here.
Within integrated photonics, various technologies exist. In order to ultimately get the optimal result for the intended application – and thus be able to make money – it is essential to combine those technologies. In such ‘heterogeneous integrations’, different semiconductor technologies are combined on a chip or on a wafer, the platform on which those chips are produced. This process yields better performance and lowers costs.
What is integrated photonics?
Photonics is similar to electronics. However, instead of electrons, it uses photons (light) to transmit information. Photonic technology detects, generates, transports, and processes light. Current applications include solar cells, sensors, and fiber-optic networks. Photonic chips, officially called Photonic Integrated Circuits (PICs), integrate various photonic and often electronic functions into a microchip to make smaller, faster, and more energy-efficient devices. Because they are manufactured like traditional chips (with wafer-scale technology), mass production is also within reach – with price drop as a result. More here.
Each technology within integrated photonics offers its own typical strengths. These can be brought together in a number of different ways, depending on the application. No single integrated technology can fill all the functions on its own; combinations are needed for maximum functionality. The range of techniques for doing that – hybrid or heterogeneous integration – is a major growth driver for the Dutch photonics industry.
Each of the three main ‘flavors’ within integrated photonics – indium phosphide (InP), silicon nitride (SiN), and silicon photonics (SiPh) – has its own strengths and weaknesses. They are complementary: for many applications, one platform cannot do without the other: they must be combined to unlock certain functionality. This includes combining them with the regular silicon chips needed to drive the photonic chips. On top of all that, increasing the performance or reducing costs can also be a reason for combinations.
Which combinations will be applied at a certain moment, therefore, depends entirely on the intended application. Gerwin Gelinck, professor at TU Eindhoven and researcher at TNO at Holst Centre, sees three major application domains for integrated photonics: telecom/datacom, automotive, and medical. “When looking at high volume applications – because that’s when the costs go down – telecom/datacom is already showing most results. It’s all about how to send as much data as possible as cheaply and economically as possible. That process takes a lot of power and generates a lot of heat. Transmitting data via light leads to a significant reduction in the use of energy. We consider it a social task of Holst Centre to contribute to this.”
Gelinck foresees an important role for the Netherlands in the development of integrated photonics: “There are some parties that are becoming very big thanks to this new technology. The universities, in particular, should be proud of that. With several photonic start-ups and semiconductor giants like ASML and NXP, the Netherlands is already at the forefront of making new products.”
One such start-up was EFFECT Photonics in Eindhoven, some 10 years ago. The company now has around 250 employees and offices in the Netherlands, England, Taiwan, and the US. Boudewijn Docter, founder, and president: “A few years ago we took the first steps in the transition from an R&D company to a production company. The next step is to produce in large quantities. We make transceivers, transmitters, and receivers in one. These can be used for medium-distance fiber optic connections from 10 to 100 km, including for 5G networks. But they also work for connections between antennas, exchanges, and the rest of the network. In addition, for connecting data centers to each other and to the Internet Exchange.”
Different colors of light
The possibilities of optical data transport can be broadened by working with different colors of light, Docter says. “When light changes color it gets a different frequency. If you send light in different colors in parallel in fiber optics, you can increase the capacity of the link. So we develop transceivers that you can set to different colors. That way you can send as many as a hundred data streams through one fiber optic cable.”
Docter is optimistic about the opportunities for the Dutch integrated photonics industry: “We have a good position in terms of knowledge and developing applications. In addition, we have a long history in the semicon industry with Philips, ASML, and NXP. On the other hand, we have less experience in scaling up photonic applications to very high volumes. Initiatives like PhotonDelta are therefore very welcome, as is government funding. If you have a successful technology platform and a government that supports its development, then you can launch many new products in a short period of time. This makes the volumes go up and the whole ecosystem benefits. We are now seeing the first companies in the Netherlands making money with integrated photonics. We have done a lot of pioneering work, experienced a lot with ups and downs. I hope it won’t take that long for other companies.”
Activity around optical chips is not limited to the world of start-ups. Take, for example, NXP, the largest producer of semiconductors for the automotive industry. The company has a rich history that began in 1953 as Philips Semiconductors, the first chip factory in Europe. Marketing director Rob Hoeben says NXP has long focused on traditional, electronic chips. “In 2006, we became independent from Philips. Around that time we did little in the way of product development for optical chips. We are catching up with that now, in part by finding out how big the market is.”
Domine Leenaerts, a researcher at NXP and part-time professor at TU Eindhoven, also sees the future for high data-rate applications in optical silicon chips. “These enable integration with classical chips, and that ultimately leads to lower costs, which will also reduce the cost per bit. The heterogeneous integration of integrated photonics with traditional silicon platforms is becoming a critical success factor.”
Both NXP colleagues also see the greatest opportunities for integrated photonics for the moment in data centers. The main reason: the increasing size of these centers causes a ‘thermal challenge’. Hoeben: “When transporting ever-larger amounts of data, more energy is generated, more heat. So more cooling is needed, which in turn costs more energy. The efficiency of data transport will be a big challenge. Because light travels faster than electricity, you can deliver the same amount of data using less energy.”
Leenaerts does warn against a rat race: “The greater the efficiency of photonic chips, the less heat is released. So you need less cooling. But there will come a time when it becomes attractive to exchange that lower cooling for transmitting more data, which in turn releases heat.”
Does NXP see a role for itself in the production of optical chips? Hoeben: “The semiconductor industry is capital-intensive. A lot of money is needed to develop new products. That’s why large volumes are important to us. Nevertheless, we are also looking at markets that are still too small for us. We do that with smaller partners. These companies enjoy working with us. If a product catches on and they want to scale up, they have us behind them.”