Tuning fork at room temperature detects terahertz radiation

Researchers at the Clausthal University of Technology (Goslar, Germany), the Laboratorio NEST (Pisa, Italy), and the University of Cambridge (Cambridge, England) have created a simple detector for terahertz radiation that works at room temperature.

Sep 1st, 2009

Researchers at the Clausthal University of Technology (Goslar, Germany), the Laboratorio NEST (Pisa, Italy), and the University of Cambridge (Cambridge, England) have created a simple detector for terahertz radiation that works at room temperature. The device is built around a miniature quartz tuning fork from a standard wristwatch; radiation modulated at the tuning fork’s natural frequency of 32,670 Hz causes the tuning fork to vibrate as a result of radiation pressure (“photon momentum”). The vibration of the tuning fork is sensed by detecting the piezoelectric current produced by the tuning fork as it vibrates.

The detector was tested using a quantum-cascade laser (QCL) as the terahertz source, which emitted on the order of 0.5 mW of 2.8 THz radiation. Because there was some crosstalk between the electronics and the tuning fork, the true reading of the detector was considered to be the measured reading minus a reading taken with all radiation blocked. The photon-momentum detector was tested against a silicon bolometer and a Golay cell, and found to have an approximately linear response over a range of about a factor of five. The detector was also used to capture scanned images. The researchers believe its best use may be as a “monitor photodiode” type detector for a QCL. Contact Ulrike Willer at u.willer@pe.tu-clausthal.de.

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