In femtosecond terahertz-pulse (T-ray) imaging of metal structures with dimensions of the order of the wavelength, it is observed that the T rays propagate faster than the vacuum speed of light. In the case of apertures this can be understood as a waveguide effect in which superluminal velocities are expected close to the cutoff frequency. However, the effect is also observed close to knife edges and in propagation past thin metal wires.
© 1999 Optical Society of America
(110.3080) Imaging systems : Infrared imaging
(320.0320) Ultrafast optics : Ultrafast optics
(320.2250) Ultrafast optics : Femtosecond phenomena
(320.5540) Ultrafast optics : Pulse shaping
(350.5500) Other areas of optics : Propagation
Klaas Wynne and Dino A. Jaroszynski, "Superluminal terahertz pulses," Opt. Lett. 24, 25-27 (1999)