Filamentation of femtosecond laser pulse in optical vortex on wavelength 800 nm in fused silica is numerically studied. Spatio-temporal intensity distributions, fluence distributions and frequency-angular spectra for optical vortex and circular beam are obtained. It is shown that filamentation in optical vortex may tend to formation of stable cylindrical structure, which length is greater than in linear case. Parameters of this structure are presented. Comparative analysis with circular beam is done, estimations of energy transformation into stokes and antistokes spectral domains are calculated.
The filamentation of focused beams at wavelength of 800 and 248 nm in air is studied experimentally and numerically. The results indicate that relatively tight focusing can lead to the coalescence of individual regions of high fluence and high plasma density that result from multiple refocusing, whereas in the case of weak focusing such regions are separated in the pulse propagation direction. The lower multiphoton ionization order in the case of UV radiation leads to a stronger effect of geometric focusing on filament formation. We show the possibility to control the parameters of femtosecond laser plasma filaments by introducing astigmatism in laser beam wavefront. Strong astigmatism can lead to the splitting of the channel into two separate regions. We demonstrate that the self-phase modulation in the thin passthrough dielectric plate decreases the distance to the filament start in air and increases the length of plasma channel.
Proc. SPIE. 6733, International Conference on Lasers, Applications, and Technologies 2007: Environmental Monitoring and Ecological Applications; Optical Sensors in Biological, Chemical, and Engineering Technologies; and Femtosecond Laser Pulse Filamentation
Atmospheric turbulence influence on stochastic filamentation of the chirped femtosecond laser pulses in the kilometer-range
propagation is analyzed. The problem of the chirped pulse parameters optimization is discussed. An effective semi-analytical method is suggested to investigate chirped pulse propagation and filamentation over kilometer range distances in the turbulent atmosphere.
We present educational programs on nonlinear optics and laser physics in the ILC MSU. These programs are aimed on both full-t ime students of physics faculty and students of retraining courses. As a part of life-l ong learning we offer different types of programs ranging from short courses to one-y ear long retraining programs. These programs include lecture courses, practical work in the training laboratories, and graduate research work in the scientific labs under a supervision of an expert. Special attention will be paid to new tendencies in the educational activities at the ILC MSU: developing and using multimedia courses, short-range practical courses in adjacent fields, constantly developing university teaching laboratory on laser physics and optics.
International laser Center of Moscow State University offers teaching setups for undergraduate students and students of retraining courses who apply photonics, lasers, and optical communication methods in different fields. Each teaching task is targeted to make a student carry out a real experiment. Most of laboratory works are intended both for phenomena demonstration and for in-depth study of physical mechanisms. The developers of the laboratory works tried to link them to the concepts from other physics courses: quantum mechanics, electricity and magnetism, solid-state physics. Laboratory experience with lasers and photonics reinforces ideas learned in these courses.
The problem of optimization of the adaptive optical system using local curvature sensor is discussed. Computer simulations of the sensor including closed-loop operation are based on ray-tracing technique and numerical solution of Poisson equation by FEM method. Wavefront restoration for both axial symmetric and non-axial symmetric phase distortions is examined. It is shown, that choosing appropriate geometry of the actuator external electrodes one can improve wavefront restoration for the case of non- circularly symmetric Zernike aberrations.
The 3D model of continuous random medium as a chain of phase screens, describing both transverse and longitudinal correlation of wave phase in a wide range of spatial scales have offered. The constructed model essentially removes the lower restriction on thickness of random medium, replaceable by the phase screen. Analysis of phase screens, received through a modified subharmonic method, has been concluded. The statistical research of random walk of a beam in turbulent atmosphere have carried out.
Two types of scattering of the laser radiation arising when an intense (1014 - 1016 W/cm2) subpicosecond ionizing pulse propagates in an atmospheric-density gas are considered: the stimulated Raman scattering (SRS) of the laser pulse by the electron plasma wave and the scattering as a result of the spatio-temporal instability in the self-produced plasma. The contributions of the spatio-temporal instability and the SRS to the laser pulse spectrum are compared.