Experts: Tobias J. Kippenberg (EPFL), with assistance from Rachel Grange (ETH Zurich)
Photonic integrated circuits allow optical signals to be directly generated, detected and manipulated on a chip. Silicon-based examples are already being used commercially in data centres. Such chips are not only more energy-efficient than conventional electronic chips, they also have a higher transfer speed and bandwidth. In recent years, the use of new materials has given rise to a new generation of photonic integrated circuits. These have the potential to revolutionise a whole range of markets. They can be used in medical devices, in space travel, in telecommunications or for measuring distance. This technology is considered groundbreaking, especially in view of the expected electricity consumption of future IT infrastructure, and it offers market opportunities – particularly for new, small yet highly specialised players.
In our information society, laser light is the main transmission medium. This light is primarily transported along optical fibres. The conventional integrated circuits that everyone knows as chips use electricity to transmit signals and consist of an array of electronic components, such as transistors, amplifiers and resistors, on a semiconductor wafer. In photonic integrated circuits (PICs), the electronic components are replaced by photonic ones and light is used for signal transmission. Photonic components include, for example, filters, laser diodes and waveguides.
Integrated photonics is currently undergoing a second revolution. Until now, only silicon-based integrated photonics has matured sufficiently to become commercially viable, and now plays a significant role mainly in short- to medium-range transceivers in data-centre networks. Silicon though, despite its enormous importance for microelectronics, is not an ideal material in terms of its optical properties, as it is lossy and cannot be used in the visible light range. Despite applications in data centres, the technology has not yet successfully been made more widely usable. That is about to change: The use of new types of materials for PICs, such as gallium phosphide, lithium niobate or silicon nitride, allows access to new wavelength ranges and new physical effects. Laser sources or modulators on such a basis make it possible to produce PICs that are smaller and more efficient, but scalable, and also more powerful than previous optical technologies. Integrated photonics could thus revolutionise a multitude of application areas. Such new types of photonic chips can be used to make optical frequency combs, which act like laser rulers for light and enable measurement of optical frequencies. These photonic integrated frequency combs are used in data centres, in ophthalmological medical devices for techniques such as optical coherence tomography (OCT), in metrology, in space travel, in assistance systems for autonomous driving (see article Autonomous vehicles) , in telecommunications and in military technology. At the same time, these PICs can also be used for basic research – e.g. in the field of quantum research. PICs constitute an enabling technology that can lead to groundbreaking developments in numerous industrial sectors.
The most recent advances have shown that integrated photonics, based on hybrid approaches and using new materials, has enormous potential that goes far beyond data transfer, e.g. in information acquisition with LiDAR sensors, for information processing within AI applications, and in sensor technology or medical technology.
The new types of PICs developed in recent years, which use new materials and combine several material systems on one chip combine light-generation, -amplification or -modulation functions with higher bandwidth, greater transfer speed and lower energy consumption. In view amount of electricity future IT infrastructure is expected to consume, they could thus become a game-changer. In order to fully exploit the potential though, the main challenges associated with integrated photonic components and the associated materials need to be overcome.
At an economic level, there are major opportunities for new companies and thus also to create new jobs. Unlike electronics, integrated photonics is a highly fragmented market, where it makes sense to specialise in niches. This means that new players can also gain a significant share of the global market – as existing Swiss integrated-photonics companies have already shown. Given the large number of highly specialised materials required, the task of assembling them, as well as specific applications and services, there are future market opportunities for dozens, or even hundreds, of companies. Moreover, the photonics market is substantial, despite its fragmentation. All in all, Switzerland could establish itself as an important development centre for the next generation of integrated photonics and is already home to significant players today.
The main obstacle for projects in the field of integrated photonics is the large amount of financing required, especially when it comes to investing in cleanrooms. Integrated photonics start-ups cannot operate or maintain their own cleanrooms owing to the enormous costs involved. Flourishing start-ups at successful locations such as Stanford, Twente and Santa Barbara use university cleanrooms. However, this requires cleanrooms with rigid process control that ensures external users are granted access. For reliable and reproducible processing, the cleanroom infrastructure must be adapted to avoid a mixing of processes.
For computers with greater bandwidth requirements, the use of these second-generation PICs will massively increase computing power. Not only do they have the potential to revolutionise the laser market, which is still based on conventional technologies like optical fibres and partly on manual manufacturing, but this second generation of PICs can also be used to build new types of optical computers, as well as metrology labs on a chip, and enables new types of sources for generating microwave signals, as required for 5G or 6G networks.
The networking among the relevant players is inadequate. For instance, there is no National Centre of Competence in Research or other focused programme for the development of next-generation integrated photonics. Developments in this field require high levels of investment, not only in staffing but also in the very cost-intensive cleanroom technology that is needed. Conventional research funding in Switzerland is not providing sufficient resources for projects.