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Illustration: NASA WMAP Team
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Solid-State THz Sources (CW)
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Y. R. Shen University of California, Berkeley Optical rectification of intense laser pulses
Gerard Mourou University of Rochester Generation of picosecond electrical transients Time-resolved measurements with far-IR radiation
David Auston Columbia University, New York Picosecond pulses from photo- conductive switches (the Auston switch)
Daniel Grischkowsky Oklahoma State University Free-space THz transients Optical THz technology THz time-domain spectroscopy
q x
y E
E!qx
y
!
Now we look closer at a single field line:
The charge q is accelerated for a short time !t, we look again a bit later:
The information about the moving charge propagates at the speed of light. This leads to a kink in the field that propagates away from charge at the speed of light. (LIGHT!)
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Heinrich Rudolph Hertz (1857-1894)
Karlsruhe, 1887:
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2424
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15.09.2008Terahertz Technologies and Biophotonics11
Geometry of a broadband THz antenna
Auston switch(1984)
Semiconductor substrate
+
E
• Electrodes are defined on a semi-conductor surface by UV or e-beamlithography and metal evaporation.
• There is a bias applied across the electrodes.
• The photoconductive region between the electrodes is excited by a femtosecondlaser.
• The transient photocurrent leads to emission of THz radiation.
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THz image of a packaged semiconductor integrated circuit
THz image of a freshly cut and 48 hours old leaf
Hu and Nuss, Opt. Lett. 20, 1716 (1995)
THz transmission image of a Hershey bar
THz time delay image of a Hershey bar
Mittleman et al. Appl. Phys. B 68, 1085 (1999)
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Visual inspection: Nothing dangerous!
THz picture: hidden knife is visible.
[Source: QinetiQ, http://www.qinetiq.com]
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http://frhethz.physik.uni-freiburg.de
Mummified hand
THz-Transission at 0.16 THz
Lena Öhrström, P.D. Dr. Dr. Frank Rühli
Klinische PaläopathologieMedizinhistorisches Institut, Universität Zürich
X-ray
THz-pulse delay image
II
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11Monday, October 5, 2009
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