The fundamental solution of the unidirectional pulse propagation equation

The fundamental solution of a variant of the three-dimensional wave equation known as "unidirectional pulse propagation equation" (UPPE) and its paraxial approximation is obtained. It is shown that the fundamental solution can be presented as a projection of a fundamental solution of the wave equation to some functional subspace. We discuss the degree of equivalence of the UPPE and the wave equation in this respect. In particular, we show that the UPPE, in contrast to the common belief, describes wave propagation in both longitudinal and temporal directions, and, thereby, its fundamental solution possesses a non-causal character.Comment: accepted to J. Math. Phy

Terahertz and far infrared radiation generation in air plasma created by bichromatic subpicosecond laser pulses

Here, we report on terahertz (THz) radiation generation in air driven by the fundamental and second harmonic of Yb:KGW laser pulses with durations of a few hundred femtoseconds. It was found that the spectrum of generated THz pulses surprisingly spans up to 50 THz, which is comparable to that usually obtained using much shorter Ti:sapphire laser pulses. The broad bandwidth is attributed to a strong spatiotemporal reshaping of the pump pulses in a filament. The achieved energy conversion efficiency is comparable to the one usually obtained from much shorter pump pulses and could be further improved by an optimized experimental setup. The obtained results indicate that compact Yb-based sources provide an attractive alternative to much larger and expensive laser systems

Diagnostics and Correction of Pre-Competition Psychological Readiness of Judoists of Dif-ferent Qualifications

The paper contains experimental materials on diagnostics and correction of pre-competition psychological readiness of judoists of different qualifications. The diagnostics of pre-competition psychological readiness is carried out during the whole pre-competition mesocycle - at the beginning and at the end of every micro cycle. The results of the diagnostics underlie the development of individual contents of correctional work for every sportsman. The contents of the correctional work can have substantial differences depending on the sport qualifications of a judoist and the completeness of separate components of his/her mental preparation. In order to verify the effectiveness of the developed contents of correctional work we have carried out three pedagogical experiments with judo sportsmen of different sport qualifications. The correctional work has been done with judo sportsmen of different sport qualifications during these three competition periods; it allowed us to achieve the completeness of each structural component of mental preparation, which in its turn contributed to the achievement of optimal pre-competition psychological state of judoists; adequate reactions during the fight; improvement of the judoists` performance.В статье представлены экспериментальные материалы диагностики и коррекции предсоревновательной психологической подготовленности дзюдоистов различной квалификации. Диагностика предсоревновательной психологической подготовленности проводится на протяжении всего предсоревновательного мезоцикла - в начале и после окончания каждого микроцикла. Полученные результаты диагностики служат основой для разработки индивидуального содержания коррекционной работы для каждого спортсмена. Содержание коррекционной работы имеет существенные отличия в зависимости от спортивной квалификации дзюдоиста и сформированности отдельных компонентов психологической подготовленности. Для проверки эффективности разработанного содержания коррекционной работы было проведено три педагогических эксперимента с дзюдоистами различной спортивной квалификации. Проведение коррекционной работы с дзюдоистами различной квалификации в течение трех соревновательных этапов позволило добиться желаемой сформированности каждого структурного компонента психологической подготовленности. Это, в свою очередь, способствовало созданию оптимального предстартового состояния дзюдоистов; адекватному реагированию в процессе ведения схватки, повышению результативности соревновательной деятельности дзюдоистов

Strong terahertz emission from electromagnetic diffusion near cutoff in plasma

Anew mechanism for electromagnetic emission in the terahertz (THz) frequency regime from laser-plasma interactions is described. A localized and long-lasting transverse current is produced by two counter-propagating short laser pulses in weakly magnetized plasma. We show that the electromagnetic wave radiating from this current source, even though its frequency is close to cut-off of the ambient plasma, grows and diffuses towards the plasma-vacuum boundary, emitting a strong monochromatic THz wave. With driving laser pulses of moderate power, the THz wave has a field strength of tens of MV m(-1), a frequency of a few THz and a quasi-continuous power that exceeds all previous monochromatic THz sources. The novelty of the mechanism lies in a diffusing electromagnetic wave close to cut-off, which is modelled by a continuously driven complex diffusion equationopen

Experimental evidence of strong phonon scattering in isotopical disordered systems: The case of LiH_xD_{1-x} crystals

The observation of the local - mode vibration, the two - mode behavior of the LO phonons at large isotope concentration, as well as large line broadening in LIH - D mixed crystals directly evidence strong additional phonon scattering due to the isotope - induced disorder.Comment: 9 pages, 4 figure

Soliton compression and supercontinuum spectra in nonlinear diamond photonics

We numerically explore synthetic crystal diamond for realizing novel light sources in ranges which are up to now difficult to achieve with other materials, such as sub-10-fs pulse durations and challenging spectral ranges. We assess the performance of on-chip diamond waveguides for controlling light generation by means of nonlinear soliton dynamics. Tailoring the cross-section of such diamond waveguides allows to design dispersion profiles with custom zero-dispersion points and anomalous dispersion ranges exceeding an octave. Various propagation dynamics, including supercontinuum generation by soliton fission, can be realized in diamond photonics. In stark contrast to usual silica-based optical fibers, where such processes occur on the scale of meters, in diamond millimeter-scale propagation distances are sufficient. Unperturbed soliton-dynamics prior to soliton fission allow to identify a pulse self-compression scenario that promises record-breaking compression factors on chip-size propagation lengths