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Atomic Physics Seminars

ics Atomic
Monday, April 2, 2018
3:30 PM
Physics Building, Room 204
Sanjay Khatri [Host: Bob Jones]
UVA-Department of Physics
"THz enhanced Surface Second Harmonic Generation"

When a material is exposed to an intense laser field, the absence of inversion symmetry at the surface can result in the formation  of a non-linear surface polarization and surface second harmonic (SSH) emission. We find that the SSH yield from a metal can be dramatically influenced by the presence of an additional THz field. In the experiments, collinear 100fs 780nm laser and 2ps single-cycle THz beams are focused at grazing incidence along a gold surface. The SSH yield is measured as a function of the THz intensity, relative laser-THz delay, and laser/THz polarizations relative to the surface normal. The yield from an optically flat gold mirror increases by as much as a factor of three in the presence of a 20kV/cm THz eld. Interestingly, the SSH enhancement for the same THz field is as large as a factor of 27 if the gold mirror is replaced by a gold-coated diffraction grating, apparently due to either a local THz field enhancement or increased sensitivity of the non-linear polarization to the THz field near grating micro-structures. We are exploring the use of THz-enhanced SSH emission to characterize the THz-field enhancement and/or response of micro-structured metal surfaces with other geometries.

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