| Abstract [eng] |
Supercontinuum generation is a remarkable nonlinear phenomenon which can be observed in transparent media during propagation and filamentation of intense ultrashort laser pulses and can be described as an extreme spectral expansion caused by an intricate interplay of various physical processes. This dissertation aims to investigate femtosecond filamentation and supercontinuum generation in narrow energy band gap dielectric and semiconductor crystals in the near- and mid-infrared spectral range. Firstly, a compact mid-infrared laser source for supercontinuum generation based on difference frequency generation was developed. Also, a simple method for evaluation of material nonlinear refractive index was proposed by measurement of nonlinear energy transmission during femtosecond filamentation. It was shown that narrow band gap dielectrics such as mixed thallous halides together with undoped semiconductor crystals such as silicon and silicon carbide are suitable materials for efficient supercontinuum generation in the infrared spectral range. In addition, it was demonstrated that pulse splitting during supercontinuum generation in silicon crystal with input pulse wavelength falling in the normal group velocity dispersion region of the material is a universal physical characteristic of femtosecond filamentation in undoped semiconductors as well as in dielectrics. Lastly, it was shown that ultrabroadband multi-octave infrared supercontinuum spectra generated in alkali metal halide crystals are prone to a rapid narrowing due to color center formation which effectively decreases the energy band gap. |
