A.A. Skorynin

Dynamical Bragg diffraction of optical pulses in photonic crystals in the Laue geometry: Diffraction-induced splitting, selective compression, and focusing of pulses

A theory for the dynamical Bragg diffraction of a spatially confined laser pulse in a linear photonic crystal with a significant modulation of the refractive index in the Laue geometry has been developed. The diffraction-induced splitting of a spatially confined pulse into the Borrmann and anti-Borrmann pulses localized in different regions of the photonic crystal and characterized by different dispersion laws is predicted. The selective compression or focusing of one of these pulses with the simultaneous broadening or defocusing of the other pulse is shown to be possible.

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

The polarization effects in the diffraction-induced pulse splitting (DIPS) observed under the dynamical Bragg diffraction in the Laue geometry in linear one-dimensional photonic crystals (PCs) are studied theoretically and experimentally. It is demonstrated that the characteristic length of the laser pulse path in a PC, or splitting length, used to describe the temporal pulse splitting, as well as the number of the outgoing femtosecond pulses, are influenced significantly by the polarization of the incident laser pulse. We have observed that the characteristic splitting time in porous quartz PCs for the s-polarized probe pulse is approximately 1.5 times smaller as compared with that measured for the p-polarized radiation. These results are supported by the theoretical description and ensure that the polarization sensitivity of the DIPS effect is due to a large lattice-induced dispersion of the PC. It is also shown that the number of output pulses can be varied from two up to four in both transmission and diffraction directions depending on the polarization of incident femtosecond pulses.

Diffraction-induced laser pulse splitting in a linear photonic crystal

We demonstrate analytically a linear optical property of photonic crystals--diffraction-induced incident optical pulse splitting in two pulses propagating with different group velocities in a linear photonic crystal. The reason of this phenomenon is in spatially inhomogeneous field localization within the photonic crystal in case of the Bragg diffraction at the Laue scheme. The field of the fast first pulse is mainly localized within low refractive index layers, whereas the slow second pulse field is mostly in high refractive index layers. Changing optical properties of either high-index or low-index layers of periodical multilayer structure, it is possible to control parameters of each propagating pulse separately. The distance between two transmitted and two diffractively reflected output pulses can be controlled by varying the crystal thickness and modulation depth of the refractive index.

Experimental demonstration of selective compression of femtosecond pulses in the Laue scheme of the dynamical Bragg diffraction in 1D photonic crystals

We present the experimental results of diffraction-induced temporal splitting of chirped femtosecond optical pulses under the dynamical Bragg diffraction in the Laue geometry. For the experiments we made a transparent, high quality porous-quartz based 1D photonic crystal composed of 500 layers. We demonstrate that a selective compression of pulses is observed in this case, that is only one pulse from the pair is compressed, while the second one is broadened. This selective compression effect is determined by the sign and the value of the chirp parameter of the input pulse, in agreement with the theoretical description.

Gap soliton and quasi-linear 2π pulse in continuous resonant photonic crystals

Nonlinear interaction of coherent intensive optical radiation with continuous resonant photonic crystal (RPC) is analytically and numerically studied in the framework of semiclassical approach using the two-wave Maxwell–Bloch equations. The analytical solution being the gap soliton of self-induced transparency is obtained in the case of an initially unexcited continuous RPC. This solution is confirmed numerically. Influence of both initial inversion and resonant atom concentration function profile on the pulse dynamics in continuous RPC is analyzed. Suppression of the Bragg reflection and a “quasi-linear” 2π pulse propagation in the case of zero initial inversion in continuous RPC is shown. The possibility of laser pulse compression using slow spatial changing of resonant atom concentration is demonstrated.

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.

Diffraction-induced spatially confined laser pulse splitting in photonic crystals

It is shown theoretically that the effect of diffraction-induced optical pulse splitting in a linear photonic crystal under the conditions of the Laue transmission geometric scheme of Bragg diffraction can be realized for a spatially confined laser pulse in a hundred-period multilayer structure.