Graphene for Photonics and Optoelectronics Applications
Torkel Nord Bjärneman offers his insights on graphene applications in photonics and optoelectronics.
Q: What is the current state of graphene for photonics/optoelectronics applications?
Despite graphene and related materials' relative youth, we are already starting to see products available on the market that make use of their properties. The development and commercialisation of disruptive photonic and optoelectronic technologies usually takes a very long time. Graphene has proved to be a key enabler for innovation in this field, because it operates at an extremely broad spectral range, which means it can interact with many different 'colours' and wavelengths of light. Moreover, it exhibits both electro-absorption and electro-refraction of light and is compatible with existing silicon photonics. This makes graphene ideal for optical and data communication components, such as transceivers, modulators and photodetectors. In this field, the aim is to have optical transceivers integrating waveguides with photodetectors and modulators. Achieving this with graphene would be a radical, and important, accomplishment. Current technologies on the market will not meet the future demands of speed, bandwidth and power consumption projected by experts in the field. Graphene also has potential in transparent electrodes for displays, imaging technologies and solar cells, where graphene-based imaging technologies are already on the market. The Graphene Flagship currently has four active Spearhead Projects (METROGRAPH, GBIRCAM, AUTOVISION and GRAPES) focusing on these applications. Led by key European industry players, these will bring graphene-enabled technologies closer to market. In addition, the Graphene Flagship recently launched the Experimental Pilot Line for graphene-based electronics, photonics and sensors, which is undertaking the manufacturing and scale up challenges for graphene-based devices. Having more industry players involved certainly validates the promise of graphene-based photonics and optoelectronics and shows that we are getting closer to commercialization.
Q: What challenges does graphene face in becoming integrated in photonics/optoelectronics?
As many of the promising graphene-based photonic and optoelectronic devices rely on single-layer graphene, manufactured using chemical vapour deposition, it is crucial that we find solutions to the technological challenges that still exist. For example, the graphene community needs to optimize high-quality growth, transfer tools (which can guarantee high yield and integrity) and processes to fabricate devices at the wafer scale. Then we will see market adoption for these technologies. Aside from graphene, there are similar challenges for other layered materials, such as hexagonal boron nitride and transition metal dichalcogenides (such as molybdenum disulfide and tungsten disulfide). These are important since they can complement the possibilities of graphene.
However, not all challenges are technological – some of them come from the target markets themselves and some at the industry level. For example, some of the markets where graphene-based photonic devices could be introduced can be classified as quasi-monopolistic. There, suppliers move in buoyancy with each other and are unlikely to take on a high level of risk. New, disruptive technologies create risks for these suppliers, so the barrier for the acceptance of new technologies is, unfortunately, high.
Finally, on the industry level, there is a need for standardisation. This is not specific to photonic and optoelectronic applications but is still relevant: standards are needed for terminology, characterisation, processes and quality control so that we can fabricate high-quality graphene-based devices and ensure reliable communication along the supply chains. The Graphene Flagship Standardisation Committee was put into place to tackle this challenge.
Q: What are the most promising graphene photonics/optoelectronics products currently on the market?
The photonics and optoelectronics industry is a complex environment, with several challenges that make commercialisation slower. That being said, one company that has succeeded is Graphene Flagship partner Emberion, which delivers high-performance camera cores that are built around in-house developed infrared imagers based on layered materials and custom designed complementary metal-oxide-semiconductors (CMOS) readout integrated circuits (ROIC). Emberion exploits the properties of graphene and related materials by integrating them in their unique sensor solutions. They are currently offering visual to short-wave infrared (VIS-SWIR) and mid-wave infrared (MWIR) detectors. Emberion is also the lead for the GBIRCAM Graphene Flagship Spearhead Project, which aims to develop a graphene-based broadband imager.
We are also seeing companies that are paving the way towards commercialisation. One of them is Graphene Flagship partner Aixtron, which delivers chemical vapor deposition systems to many of the suppliers of this type of graphene. And we can also see promising start-up companies such as Graphene Flagship Associate Members CamGraPhIC and Nu Quantum, and Graphene Flagship partner CRIL Technology, working their way towards commercialisation.