Research

The Terahertz laboratories are actively involved in creating new emitters and detection techniques at terahertz frequencies.

Optical Gating of Graphene

We demonstrate experimentally nonvolatile, all-optical control of graphene’s charge transport properties by virtue of an Fe:LiNbO3 photoconductive substrate. The substrate can register and sustain photoinduced charge distributions which modify locally the electrostatic environment of the graphene monolayer and allow spatial control of graphene resistivity.

see publication

https://pubs.acs.org/doi/10.1021/acsnano.8b02161

Novel emitters

Research involving the creation of new THz antennas, particularly antennas that do not require electrical bias signal. Currently, the group is focussing on antennas that utilise the lateral photo-Dember effect, where the diffusion of photo-excited carriers is responsible for the emitted THz waves.

THz Quantum Cascade Amplifier

Terahertz quantum cascade lasers (THz-QCLs) are promising sources of THz frequency waves. While the research surrounding the commercial deployment of QCLs as THz sources is in its infancy, our group is working on using a QCL’s active region as an amplifier of THz signals.

THz Polariton laser

A THz polariton “laser” is a THz source that relies on nonlinear conversion of a semiconductor band-gap emission wavelength using polaritons. A polariton is a photon strongly-coupled to an electron-hole pair, which is typically achieved using a microcavity. Whilst it does not utilise stimulated emission to amplify light, the resulting emission exhibits all the properties of light commonly associated with laser light, including coherence and narrow linewidth.

Novel THz emitters

The photo-Dember (PD) effect is a THz emission mechanism based on ultrafast carrier transport. THz radiation is produced by illumination of a semiconductor surface by an ultrafast near infrared laser with energy above the bandgap (usually Ti:S). The strong absorption of light near the surface creates a large carrier gradient of electrons and holes, which …

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THz Quantum Cascade Amplier

Currently, most commercial THz spectrometers are time-domain spectrometers (TDS), where THz pulses are generated on antennas by a photocurrent created from a pulsed laser. The detection scheme uses a similar antenna where carriers are generated by the same pulsed laser. The advantage of this apparatus is that the detection scheme is synchronous: the receiver is …

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