Continuously tunable Dual Color DFB Laser System for characterization of epitaxial graphene devices at THz frequencies

Graphene is a new material with promising applications in high frequency electronics and optoelectronics. Potentially, active graphene devices can reach operation speed of picoseconds. High frequency transistors and opto- electronic modulators have been reported however in a modest frequency range limited only by tens of gigahertz. A study of graphene at terahertz frequencies, being a challenging task, is of very important, both fundamentally, from the point of interaction of high frequency radiation with a new electronic system, and practically, since terahertz range itself is a rewarding field of deep space observation, security and health screening.
The main objective of the proposed research is to build new capabilities of far- and mid- infrared optoelectronics technology based on epitaxial graphene. RHUL carries an extensive research in a field of THz technology, including detectors, sources and optics, with the aim at THz imager for security and health screening. There are in place a wide range of technologies and expertise: nanofabrication facilities, low temperature experimental set up, THz spectroscopic equipment, sensitive THz detectors and sources. Semiconductor hetero-structures with high mobility 2DEG and superconductors were the prime materials of the terahertz research until recently. We expand this with a new material, the epitaxial graphene. The epitaxial graphene (G/SiC) is produced at standard SiC wafer by annealing in Ar atmosphere. In contrast to the flakes of graphene widely used for research, the G/SiC has a macroscopic size, and it is compatible with industrial nanofabrication technology. The SiC/G has a strong coupling to the SiC substrate, which makes it different from the exfoliated graphene: it has a non-vanishing n-doping, proximity of substrate affects optical properties of graphene, particular in the mid- infrared range where SiC has a sharp absorption edge. We aim to utilize these properties in a new generation of devices, like fast optical switches, generators and detectors of high frequency radiation. Study of high frequency operation of epitaxial graphene is in progress already in collaboration with National Physical Laboratory. We investigate plasmon and magneto-plasmon response of the G/SiC in application to mid and far-infrared detectors and sources. Theoretical support is provided from a leading graphene research group at Lancaster University. The work involves international collaboration with Chalmers University in Sweden and Tokyo University in Japan.
We propose to upgrade our facilities with tunable THz laser source of bandwidth from 0.1 to 2 THz with accuracy of 0.1 GHz. This source will boost our abilities in spectroscopy of the G/SiC based devices in THz range, as well as give us inside of the fundamental high frequency properties of the material. The platform will be available for the UK organisations involving in graphene research and development. NPL and UCL are partners in the project have a complementary graphene and THz facilities. A collaborative research on high frequency operation of graphene is in progress between three organisations, RHUL, NPL and UCL.

Successful research on high frequency operation of epitaxial graphene would be a contribution to activity of UK graphene community and add to international recognition of UK scientific and technological leadership. Innovative experimental and theoretical methods developed within the project would have a transferable value for other graphene projects.

Tuneable source will expand terahertz platform at Royal Holloway. This would be unique facilities where there will be spectral tuneable terahertz source with possibility of cryogenic temperature of materials under investigation, including cryogenic detectors. The platform will support activity of RHUL in terahertz imager, where epitaxial graphene is one of component. Terahertz spectroscopy technology will be accessible for researchers working with graphene at partner organisations, NPL and UCL . This would enforce sustainability and advances of the organisations. Other UK organisations will have access to high frequency platform at RHUL.
THz research in a new material, graphene, is also a key priority for the UK with a number of companies producing equipment, to mention a few: TeraView, ThruVision.


A graphene topic is attractive to general public. A successful development of graphene devices with a high market output would foster public interest in UK high tech economy. A poster featuring the project will be prepared and disseminated at Science Open Days