Study explores terahertz sensor use

US Air Force Office of Scientific Research-funded professors Mark L Brongersma of Stanford University and Stefan A Maier of Imperial College are investigating new applications for terahertz sensors.

Based on their research, these sensors could be used for improving optical sources, detectors and modulators for optical interconnections, and for creating biomolecules.

Brongersma’s work is based on the ability of nanometallic or plasmonic structures to concentrate light into deep-subwavelength volumes.

‘Currently, photodetectors, modulators and other chipscale devices are limited in their size by the fundamental laws of diffraction but, with plasmonics, we can make much more compact devices with one to two orders of magnitude better performance parameters,’ said Brongersma. ‘As the size of these devices determines their operation speed and power, it’s hard to make much more efficient devices.’

Maier has demonstrated plasmon waveguides on a silicon platform operating in the telecom band and, under AFOSR support, he has realised some of the first plasmonic devices operating at THz frequencies.

‘The telecom band is important since that’s where data communication is taking place by means of optical fibres and the internet; the silicon platform is significant because most chips are made of that material,’ said Maier. ‘THz frequencies are vital for their sensing of dangerous substances, including plastic explosives and anthrax.’

The study of plasmonics is bringing these scientists together as each works on fundamentals, information and biotechnology.

‘Our team is working on demonstrating plasmon waveguides and cavities for a wide variety of applications spanning the electromagnetic spectrum from the visible to the microwave regime,’ said Maier.

Brongersma’s group has worked on the basic concepts behind plasmonics-enabled light concentration and manipulation and is exploring a range of applications, including faster computer chips, nanostructures synthesis, solar cells, water splitting using photoelectrochemistry, quantum optics and sensing.