Polarization and nonlinear effects in diffraction-induced laser pulse splitting in one-dimensional photonic crystals

In this paper, the polarization effects in diffraction-induced pulse spliiting (DIPS) phenomenon in porous-quartz based 1D photonic crystal (PC) are studied both experimentally and theoretically. The PC was formed with the thickness of each layer of 390 nm and with the period of 780 nm. We made the PC composed of 375 layers, so that the total PC thickness a = 300 μm was large enough for the performance of the experiments in the Laue geometry. The 110 fs light pulses at the wavelength of 800 nm generated by a Ti-sapphire laser were used. The paper demonstrates that the difference in the group velocity of the Borrmann and anti-Borrmann modes is substantially different for the p- and s-polarized pulsed radiation due to a large lattice-induced dispersion in a PC. This leads to a significant change in the value of the splitting time t₁₂ for p- and s-polarized laser pulses propagating within a PC and, in general, in the number of the outgoing pulses as well. After passing a PC the number of outgoing pulses can be varied from two up to four in both transmission (T) and diffractive reflection (R) directions, depending on the polarization of the incident radiation and the parameters of a PC. It is shown theoretically that an important point here is that due to a large value of the lattice-induced dispersion in the PC not only the first term in the expansion of the polarization factor should be considered, but the second one as well, that describes the unusual polarization dependence of the DIPS effect. The results of the theoretical description stay in a good agreement with obtained experimental data. It has been shown theoretically that in a case of nonlinear light-matter interaction for example in low-index layers one of the pulses, the Borrmann pulse, propagates like soliton keeping its shape and constant velocity whereas second pulse, the anti-Borrmann pulse, demonstrate a linear dynamics in dispersive medium.