V. B. Karasev

Application of ultrashort laser pulses in dentistry

The results of investigation of ultrashort Nd-laser pulses interaction with hard tooth tissues are represented. The values of laser radiation induced destruction thresholds and efficiencies of laser processing of enamel and dentin are measured. The results of observation of nonlinear optical effects of second harmonic generation and continuum generation in enamel and dentin below the damage thresholds are reported.

Resonators with field rotation

Basic features of laser resonators with field rotation are discussed. Main types of schemes of resonators providing high performance and low sensitivity to misalignment are represented. Results of investigation, development and application of resonators with field rotation to various laser systems are reported.

Optimizing the action of laser radiation on soft biological tissues

The slow heating of human skin by laser radiation is mathematically modelled. It is shown that blood flow has an effect on the temperature variation of the skin tissues during heating. The wavelength of the laser radiation is optimized for uniform therapeutic heating of subcutaneous structures.

The use of movable stops when forming layers of variable thickness

This paper discusses the possibilities of determining the thickness distribution of layers over the surface of a substrate when stops are used whose radius and distance from the evaporator vary with time. The characteristic thickness distributions of the layers are presented for certain positions of the stop relative to a thin annular surface evaporator. The effect of varying the size and position of a stop on the thickness distribution of a layer over the substrate surface is analyzed.

Influence of phase distortion of soft-edge ouput mirror on the characteristics of laser modes of unstable and plane-parallel resonators

This work analyzes the influence of phase distortions caused by variable-reflectivity multilayer dielectric mirrors on the spatial and energetic characteristics of the output radiation of lasers with unstable and plane-parallel resonators. The phase distortion of such mirrors has been considered in dependence on design parameters of optical coating. Some application peculiarities of soft-edge mirrors for the Cassegrain and Fabry-Perot resonators of lasers are discussed. The work represents some recommendations for the mirror design that ensures the optimal output laser beam characteristics.

Synthesis of laser beams with minimum near- and farfield divergence

In the present paper the laser beams with Cartesian symmetry having the minimum diffraction divergence in near and far fields are synthesized. The spatial sizes of these beams in near field as well as the angular size in far field have been defined on the share of total beam energy that could be transmitted within this size. It is shown that the laser beams with minimum near-field diffraction divergence are well approximated by coherent superposition of a few number of lowest symmetric Hermite-Gaussian modes. The transverse distributions of light waves with minimum far-field divergence are described by prolate spheroidal functions.

Powerful pulsed solid state lasers for lidar systems

In the present work some results of work carried out in LASER CENTER of St. Petersburg State Institute of Fine Mechanics and Optics are represented. This R and D work has been aimed on creation of powerful flash-lamp pumped solid- state lasers with advanced exploitation parameters that may be installed on different kind of moving stations. The main attention with be paid to two laser systems that are quite different but indicate practically all the field of development of powerful solid-state lasers.

Application of portable optical laboratory in high schools and colleges

The present paper describes the experience of application of portable optical laboratory in optical practicum developed directly for training and demonstrations of basic optical laws and phenomena in high-schools, colleges and nontechnical universities all over Russia. The laboratory includes the portable optical platform with built-in laser and lamp sources, kit of optical components and software. These accessories provide the attractive and smart teaching in general optics during lectures, lessons and practice at schools and colleges. The portable optical laboratory provides 28 basic lab works and demonstrations in reflection, refraction, absorption and dispersion of light, interference, diffraction, polarization of light, image formation and waveguide propagation of light in optical fibers. Due to their interdependence one can teach and learn a whole course of general optics. The individual work of students and school children with optical kit stimulates and develops their creative abilities and experimental skills, as well increases the effectiveness of education. The kit is provided with optional elements for a number of extra experiments with holography, polarizing light propagation, simple optical devices etc. These extensions allow to modify the education process according to teachers point of view. The conception of optical class-room based on portable optical laboratories is discussed. The effectiveness of individual and small-group training is analyzed.

Laser destruction of demineralized dentin

The results of comparative study of laser destruction of tooth dentin caused by intensive picosecond YAG:Nd laser pulses and submillisecond YAG:Er laser radiation are represented. The dependencies of destruction threshold and efficiency of laser treatment on demineralization degree of dentin are represented. The quality of laser cavities formed in demineralized dentine slices cut across the dentin tubules is analyzed. The possible mechanisms of destruction are discussed.

Phase-locking and unstability of light waves in Raman-active crystals

Coherent Stokes pulses are generated under amplification of the spontaneous Stokes noise radiation appearing in intense laser pulses Raman scattering. Radiation intensity selflimitation under the selffocusing in Raman media is corresponded to ejection of excess power to divergent coherent Stokes components.