Photo-ionization of superlattices on dielectric surface by IR radiation

Abstract

In this paper we analyze the photo-excitation of electron sub-system of a periodic nano-structure by IR laser radiation. The nano-structure is a 1D super-lattice on surface of dielectric or semiconductor material transparent for the incident radiation. Theoretical description of the photo-excitation is based on the recent modification of the Keldysh theory adapted to the 1D case. We show that two specific regimes of the photo-excitation are possible in the super-lattices: photo-excitation suppression corresponding to decrease of the photo-excitation rate with increasing of laser intensity, and singularity regime corresponding to abrupt increase of the photo-ionization rate. Threshold of the singularity regime is calculated as function of laser wavelength and super-lattice period. The obtained results allow to propose a promising application of the super-lattices as intensity limiters for IR optical systems. In particular, we can calculate the period of the super-lattice to provide limiting of input laser intensity at required level due to multi-photon absorption by electrons of the lattice. Temperature of laser-induced heating resulted from total absorption of an incident laser pulse and diffraction distortions induced by the super-lattice are estimated to confirm possibility of utilizing the super-lattices as the intensity limiters.