Compared with other regions of the electromagnetic spectrum terahertz (THz), the frequency range between the infrared and the microwave, has been relatively neglected. A group from the Chinese University of Hong Kong and Warwick University have recently shown that broadband, large and fast modulation of THz beams is in fact possible, and can even be achieved with one very neat device.

Much effort has been spent designing cameras and spectrometers that operate at THz frequencies. They have already proved useful in airport security scanners, and for identifying underlying layers of old paintings.

One important component of these pieces of equipment are modulators, which control the amplitude or phase of a THz beam. These must operate quickly, consume little energy, give consistent modulation over a large frequency range, and produce large changes in the intensity or phase of a THz beam. Approaches so far include metamaterials, semiconductors and liquid crystal devices, none of which meet all the necessary requirements.

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