Frequency upshift via flash ionization phenomena using semiconductor plasma

Abstract

Abstract.We have demonstrated frequency upshift in the terahertz region by flash ionization. The magnitude of upshift frequency is tuned by the laser intensity. A proof of principle experiment has been performed with a plasma creation time scale much shorter than the period of the electromagnetic wave and a plasma length longer than its wavelength. Frequency upshifted from 0.35 to 3.5 THz by irradiating a ZnSe crystal with a ultra-short laser pulse has been observed.

Analysis of microwave propagation in a time-varying plasma slab with particle-in-cell simulations

“…Reference [12] gives the power conversion of the upshift wave where the plasma is a lossless medium and the collision frequency is ignored. A proportional relationship between electric field and frequency is given by…”

“…The final angular frequency w f is w w = + c k . Several proof-of-principle experiments were presented using microwaves and optical waves as sources [11][12][13], after the publication of these theoretical predictions. They also put forward two theory requirements to obtain effective frequency up-conversion.…”

“…According to the current experimental techniques, it is difficult to achieve the above two criterions to generate the plasma at the same time. For example, the rapidly created plasma is often generated by an ultrafast-pulse laser ionized gas [12]. However, the plasma length is only several tens of micron by focusing a fs laser beam to a spot size.…”