Abstract-Conductivity Induced by High-Field Terahertz Waves in Dielectric Material

B. D. O’Shea, G. Andonian, S. K. Barber, C. I. Clarke, P. D. Hoang, M. J. Hogan, B. Naranjo, O. B. Williams, V. Yakimenko, J. B. Rosenzweig

An intense, subpicosecond, relativistic electron beam traversing a dielectric-lined waveguide generates very large amplitude electric fields at terahertz (THz) frequencies through the wakefield mechanism. In recent work employing this technique to accelerate charged particles, the generation of high-power, narrow-band THz radiation was demonstrated. The radiated waves contain fields with measured amplitude exceeding $2\mathrm{GV}/m$, orders of magnitude greater than those available by other THz generation techniques at a narrow bandwidth. For fields approaching the $\mathrm{GV}/m$ level, a strong damping has been observed in ${\mathrm{SiO}}_2$. This wave attenuation with an onset near $850\mathrm{MV}/m$ is consistent with changes to the conductivity of the dielectric lining and is characterized by a distinctive latching mechanism that is reversible on longer timescales. We describe the detailed measurements that serve to clarify the underlying physical mechanisms leading to strong field-induced damping of THz radiation ($h\omega =1.59\mathrm{meV}$, $f=0.38\mathrm{THz}$) in ${\mathrm{SiO}}_2$, a bulk, wide band-gap (8.9 eV) dielectric.

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