A Terahertz Modulator

We’re all used to the changes in the properties of radio frequency systems as the frequency increases and the wavelength becomes shorter. The difference between the way an FM radio and a WiFi adapter behave with respect to their environments, for instance. But these are relatively low frequencies in the scheme of electromagnetic radiation, as you will be aware with ever shorter wavelengths those properties change further until eventually we are not dealing with something we’d describe as radio, but infrared light.

Terahertz waves are the electromagnetic radiation that lies in that area between radio frequencies and infra-red light. You …read more

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MIT Researchers Can Read Closed Books (and defeat CAPTCHA)

Ten years ago, MIT researchers proved that it was possible to look through an envelope and read the text inside using terahertz spectroscopic imaging. This research inspired [Barmak Heshmat] to try the same technique to read a book through its cover. A new crop of MIT researchers led by [Heshmat] have developed a prototype to do exactly that, and he explains the process in the video after the break. At present, the system is capable of correctly deciphering individual letters through nine pages of printed text.

They do this by firing terahertz waves in short bursts at a stack of …read more

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