[en] Equations describing second-harmonic generation under quasi-phase-matched interaction conditions in crystals with a regular domain structure are derived. It is shown that appropriate substitution of variables makes these equations exactly identical with those describing second-harmonic generation in the usual homogeneous crystals. This analogy is used to obtained an expression for the second-harmonic amplitude in the case of inexact quasi-phase-matched interaction. (nonlinear optical phenomena and devices)

[en] The method of complete reconstruction of attosecond bursts has been demonstrated for attosecond high-harmonic pulse trains. The retrieved harmonic field provided detailed information about the envelope and the individual attosecond pulses contained in the attosecond pulse train. The time-frequency analysis revealed complicated spectral chirp structures and the contribution of different quantum paths to attosecond pulse formation.

No abstract available

[en] The second-harmonic generation with laser beams transformed by internal conical refraction in a biaxial crystal was studied in a cascaded two-crystal arrangement, where the biaxial crystal transformed the input Gaussian beam and another nonlinear crystal was used for frequency doubling of the produced conical refraction pattern. Several specific second-harmonic beam profiles obtained for various positions of the nonlinear crystal along the beam propagation direction are considered and discussed

[en] Complete text of publication follows. Recently Porras and Dombi showed, by performing analytical calculations, that it is possible to freeze or to control the variation of the carrier-to-envelope phase (CEP) of propagated few-cycle laser pulses in the focal region. These methods consist in changing the variation of the beam's spot size for different spectral components at the focusing element and/or placing a dispersive slab (or medium) in the way of the propagating pulse. We developed a numerical method to calculate the electric field of the laser in these special configurations, which allowed us to simulate high-order harmonic generation (HHG) and perform phase-matching (PM) calculations for different types of CEP variations of the input pulse. The fundamental pulse at 800 nm wavelength has a FWHM of 5 fs and peak intensity not exceeding 0.4 PW/cm². HHG is assumed to take place in neon at low pressure (< 40 Torr) and the interaction medium is placed close to the focal region of the pulse. Under these conditions ionization rate remains low during HHG, thus in the PM calculations we do not take into account the dispersion due to plasma contribution and neutrals. We assume that the electric field is not perturbed during propagation and we perform PM calculations for different harmonic orders in the whole interaction region. We will present the effect of different CEP variations of the fundamental pulse on the high-harmonic spectra and will explore the possibilities to obtain strong coherent HH radiation under favorable PM conditions.

[en] We theoretically and numerically studied the off-axis Gaussian vortex beam (GVB) characteristics. The off-axis GVB scheme is utilized to generate tunable broad OAM modes using a single helical phase. The single helical phase can be easily created in the high peak power lasers using a spiral phase plate (SPP). The high peak power GVBs greatly enhances the efficiency of nonlinear wave-mixing to tune the wavelength as well as OAM modes of laser beams. Further, we propose type-II second harmonic generation (SHG) of off-axis GVB to tune the wavelength and to increase the number of OAM modes of vortex beam. Polarization-controlled broad OAM spectra is generated at SHG wavelength. This scheme is effective for control generation of a broad range of OAM spectra in the required wavelength for high-capacity and multi-channel optical communication. (paper)

[en] A method for generating non-uniformly spaced (chirped) trains of high-energy, high-contrast, femtosecond pulses is described and demonstrated. In this method a temporally stretched laser pulse is passed through an acousto-optic programmable dispersive filter (AOPDF), a birefringent plate, and a linear polarizer. It is demonstrated that linear and nonlinear variation of the pulse separation within the train may be controlled by changing respectively the third- and fourth-order dispersion introduced by the AOPDF. Programmable, non-uniform pulse trains of this type may find applications in quasi-phase matching high-harmonic generation

[en] The Conference on Super Intense Laser Atom Physics (SILAP) was held in November 2003 in Dallas, Texas. The venue for the meeting was South Fork Ranch in the outskirts of Dallas. The topics of the meeting included high harmonic generation and attosecond pulse generation, strong field interactions with molecules and clusters, particle acceleration, and relativistic laser atom interactions

[en] Complete text of publication follows. The present paper investigates the relativistic self-focusing of elliptical laser beam in underdense plasma and its effect on plasma wave and second harmonic generation. When intense laser beam interacts with plasma, then transverse intensity gradient is established on account of redistribution of carriers. This transverse intensity gradients results in generation of plasma wave and pump wave frequency. The generated plasma wave, in turn, interacts with the input laser beam and leads to generation of a second harmonic. Effect of relativistic self-focusing on the amplitude of plasma wave and second harmonic yield are also analyzed.

[en] A comprehensive study on the requirements for the highly efficient third harmonic generation (THG) and its inverse process, one-third harmonic generation (OTHG), in lossy waveguides is proposed. The field intensity restrictions for both THG and OTHG caused by loss are demonstrated. The effective relative phase ranges, supporting the positive growth of signal fields of THG and OTHG are shrunken by the loss. Furthermore, it turns out that the effective relative phase ranges depend on the intensities of the interacting fields. At last, a modified definition of coherent length in loss situation, which evaluates the phase matching degree more precisely, is proposed by incorporating the shrunken relative phase range and the nonlinear phase mismatch. These theoretical analysis are valuable for guiding the experimental designs for highly efficient THG and OTHG. (paper)