An Auston switch (also known as a photoconductive switch) is an optically gated

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

that is commonly used in the generation and detection of pulsed terahertz radiation. It is named after the physicist David H. Auston who first developed the technology at

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

in the 1960s.

Working

An Auston switch consists of a transmission line antenna with a gap that is bridged by a semiconductor. For terahertz generation, a DC bias voltage is applied across the antenna. When light from a

pulsed laser Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. Silfvast, William T. (1996). ''Laser Fundamentals'', Cambridge University Press. ...

with

femtosecond A femtosecond is a unit of time in the International System of Units (SI) equal to 10 or of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. For context, a femtosecond is to a second as a second is to about 31. ...

pulses is focused on the gap, it excites charge carriers into the semiconductor's conduction band, which are subsequently accelerated by the bias voltage. The induced acceleration from the photocurrent causes the charge carriers to radiate in terahertz frequencies, generating a pulse lasting several picoseconds For use as a terahertz detector, the switch consists of the same geometry but without the applied bias voltage. Instead, the incident terahertz pulse itself provides the bias field for the charge carriers during the interval when the switch is activated by the (much shorter) laser pulse. The induced photocurrent can then be amplified and measured. To map the entire span of the terahertz pulse, the time delay between the femtosecond pulses at generation and detection can be varied.

References

{{reflist Terahertz technology Optical devices Optoelectronics