THz metamaterial/graphene optoelectronic modulators

This project targets the realization of an innovative class of optoelectronic devices operating in the terahertz frequency range. The THz spectral region (1-10 THz correspond to vacuum wavelengths between 30 and 300 micrometers), lies between the electronics and the photonics range. This frequency range is vastly unexplored despite its huge potential in many applications, ranging from spectroscopy to communications, to imaging and astronomy. The full potential of the THz range is limited by the intrinsic hurdles inherent to working at these frequencies and by the lack of efficient devices. In particular, the basic optoelectronic building blocks, such as frequency and polarization modulators, capable of actively manipulating this radiation are currently missing, thus hindering its full exploitation in fundamental research and in industrial applications. This proposal aims to provide such tools by realizing a novel class of active integrated and efficient devices based on the interplay between metamaterial resonances and graphene. Because of their unique versatility and performance in terms of power consumption, efficiency and reconfiguration speed, these devices will be readyly implemented with already established academic /industrial environments. The main research areas where this project finds application are identified as terahertz imaging, spectroscopy, communications and quantum electronics. Terahertz imaging represents a mature technology which is currently used in diverse key sectors, ranging from security and defense, to semiconductor inspections, to non-destructive testing of pharmaceutical tables and imaging of biological samples. THz gas and solid-state spectroscopy have several applications as well: it is widely known that drugs or explosives present strong absorption features in the THz range while, conversely, plastic material are transparent to this radiation. This lends itself naturally into security screening, e.g. at airport, and into applications in drug detection. Common pollutants and greenhouse gases have unique spectral fingerprints in this frequency range, thus finding obvious applications in environmental monitoring. These devices in combination with already established sources such as the quantum cascade laser or time domain spectroscopic systems will increase the imaging capability and allow novel spectroscopic methodologies and experimental configurations. The interest in THz wireless communication stems from the saturation of the present communication frequencies and from the ambition of higher communication speed. The THz range uniquely addresses both issues, being an unallocated frequency region and with high carrier frequencies, mandatory prerequisite for achieving fast data transfer. The development of future THz communication platform, necessary passes through the development of fast and integrated frequency and polarization modulators, which are the basic components in many communication protocols. Therefore, the success of this proposal will uniquely address several future challenges in strategic public/private sectors, capable of impacting on the layman quality of life. At the same time, this proposal has the ambition to contribute to the health and progress of different academic environments such as the research area investigating novel carbon-based materials, and the quantum cascade laser community. This research in fact will help finding novel concrete implementations for 2D materials in electronic devices and establishing their utilization in the THz range. Finally, in combination with the quantum cascade laser, these devices will provide a formidable tool set for exploring novel concepts and configurations in fundamental quantum electron field, and increase the breadth of spectroscopic operations for this particular source.

The present proposal aims to exploit the terahertz (THz) frequency range through the realization of a new class of devices, namely frequency and polarization modulators. The THz spectrum, which lies between the optical and the electronic ranges, is the most promising and unexplored part of the electromagnetic spectrum. This project presents a unique opportunity to deliver a significant and beneficial academic and socio-economic impact on an international scale. Moreover, and in line with EPSRC perspectives, terahertz technology represents an area of global scientific interest and holds promise for development across a number of application domains. Thus, THz research, has the potential to deliver a significant and beneficial academic and economic impact, particularly important considering the UK industry interested in this area. Because of the relative infancy of this technology and of the inherent difficulties in designing efficient active devices operating in this frequency range, an optoelectronic platform capable of efficiently modulate this radiation is currently missing. This proposal aims to resolve this issue, by providing to the scientific and industrial community an innovative class of devices for the frequency/polarization modulations of this radiation. The main research areas where this project finds applications are identified as terahertz imaging, spectroscopy and communications. These fast expanding areas present a natural link with many industrial activities and with public strategic sectors. Terahertz imaging represents a fast growing, mature technology which currently used in various key sectors, such as security and defense, and for the non-destructive testing of pharmaceutical tables and of biological sample analysis. A real-time monitoring of tablets' coating integrity and uniformity would help designing novel, more efficient drugs and provide a useful feedback to the pharmaceutical companies. Accordingly, this research has also the potential to impact in the field of diagnostics and healthcare by increasing the imaging capability of this radiation, with obvious impact in the layman's quality of life. The realization of more complex and complete imaging systems in the terahertz, where explosives and drugs have also unique fingerprints, while plastics and other common materials are transparent, has implications in security, e.g. in airport scanners, thus holding a clear commercial interest. The interest in THz wireless communication stems from the saturation of the present communication frequencies and from the ambition of higher communication speed. The THz range uniquely addresses both issues, being an unallocated frequency region and with high carrier frequencies, mandatory prerequisite for achieving fast data transfer. Depending on the THz communications range targeted, this radiation can be used for communications between geostationary satellites or local communication in public hotspots, such as universities or hospitals. Standard communication protocols require fast, integrated low-power consumption modulators. Therefore, the development of this sector necessarily passes through the realization of the proposed devices. This project, with the support of the academic and commercial partners, aims to increase the horizon and capabilities of all these applications. This proposal will also have a significant impact on the PhD students and Postdoctoral researchers involved, training them in experimental techniques, and bridging the gap among different research areas, e.g. graphene and THz community.