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Shaping of a Terahertz Pulse
by a Slit in a Thick Screen

This movie shows a numerical simulation of a terahertz (THz) pulse passing through a slit in a conductive screen, and the resulting diffraction. The 1-D plot below shows the electric field evaluated on a line through the center of the slit.

Thick Aperture Diffraction

The shape of the THz pulse transmitted through such a "slit filter" depends on the slit width and the screen thickness.

Here, the screen thickness of the filter is much more than the slit width. In this limit the slit filter behaves like a planar waveguide; the filtering results from the modal cut-off frequency of the waveguide, not the diffraction after the pulse leaves the filter.

Indeed, if you watch the pulse as it passes between the edges of the slit, you can see the pulse spread out as the modal dispersion causes it to fall apart.

The adjustable slit filter was formed between the edges of two copper sheets oriented parallel to the direction of polarization of the THz pulse. The thickness of the copper sheet was 1.7 mm and the slit width was 0.5 mm. The filter was 10 cm from the emitter, ensuring an approximately planar wavefront over the slit widths of interest.

To verify our experimental findings, we numerically simulated the propagation of the THz pulse through the slit using the Finite - Difference Time - Domain method (FDTD). To facilitate direct comparison of experiments and simulations, we used actual experimental parameters together with the measured input field as the starting point for these simulations.

Terahertz pulses have become important to the atomic physics community because they provide an ultra-short, single-directional "kick" to the atoms with which they interact.

More information on the diffraction of terahertz radiation by an aperture can be found in the papers:

Spatiotemporal shaping of terahertz pulses
Jake Bromage, Stojan Radic, G. P. Agrawal, C. R. Stroud, Jr.,
P. M. Fauchet, and Roman Sobolewski
Opt. Lett. 22, 627 (1997).

Spatiotemporal shaping of half-cycle terahertz pulses
by diffraction through conductive apertures of finite thickness

Jake Bromage, Stojan Radic, G. P. Agrawal, C. R. Stroud, Jr.,
P. M. Fauchet, and Roman Sobolewski.
JOSA B 15, 1953 (1998).

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Shaping a THZ pulse
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Hideomi Nihira ( nihira@optics.rochester.edu ).
Last modified 13 September 2006