Ultrafast re-structuring of the electronic landscape of transparent dielectrics: new material states (Die-Met)

Abstract

The swift excitation of the transparent dielectrics by intense short laser pulse produces ultra-fast re-structuring of the electronic landscape generating a wealth of material states continuously changing in space and in time in accord with the variations of the intensity. These unconventional transient material states combine simultaneously dielectric and metal properties (Die-Met). The laser excitation transforms a transparent dielectric into electrically inhomogeneous state early in the pulse time [1]. The permittivity of excited material varies in time and in space changing from positive to negative values that strongly affects the interaction process. The interplay between the transient permittivity gradient and polarisation of the incident laser becomes the major process of the new interaction mode. In a particular relation between the polarization and the permittivity gradient the incident field amplitude grows up while the wave is approaching to the surface where the real part of permittivity turns to zero. That results in the local increase in the absorbed energy density. The complex 3D structure of the permittivity makes a transparent part of excited dielectric (at ${\epsilon}0 > {\epsilon}re > 0$) optically active. The electro-magnetic wave passing through such a medium gets a twisted trajectory and accrues the geometric phase [2]. The plane of polarisation rotation and phase depends on the 3D permittivity structure [3]. Measuring the polarisation and phase of the probe beam allows quantitatively identify this new transient state. We discuss the revelations of this effect in different experimental situations and possible applications.