Alexander V. Fedin

Powerful neodymium lasers with the self-phase-conjugation

The powerful neodymium lasers with the self-phase-conjugation (SPC) and passive Q-swither are submitted. It is shown, that the application of a LiF:F2- crystal as Q-swither and SPC-mirror simultaneously, and also a Sagnac interferometer as end reflector of the cavity allows to increase efficiency and quality SPC-radiation. High power and spatial laser characteristics are obtained: Nd:YAG laser -- 114 W average power at 0.5 mrad beam divergence; Nd:YAP laser -- 51 W average power at 1.2 mrad beam divergence; Nd:Glass laser -- 18 J in pulse train at 1 mrad beam divergence.

Technological Nd-lasers with passive Q-switches based on LiF:F2 crystals

A new class of high power solid state lasers on neodymium containing media with passive Q- switches on LiF:F2- crystals was investigated. The generation regimes and the technological possibilities of such lasers were studied.

A method for controlling the phase locking of a multichannel laser system

The conditions leading to control over phase-locked oscillation in a set of three loop lasers containing self-pumped phase-conjugate gain-grating mirrors by using a LiF: F2− passive Q-switch are studied both experimentally and theoretically. Cases of spatially uniform lamp pumping and high-efficiency spatially nonuniform transverse diode pumping are considered.

Principles of laser drilling with adapted control over the parameters of repeated laser pulses

Principles of laser drilling of deep holes with adapted control over the parameters of the multipulse laser irradiation are determined. In good agreement with earlier experimental results, the possibilities for increasing the depth and productivity of the laser treatment of deep cavities via controlled modulation of the Q-factor and active synchronization of the modes of a high-power single-mode YAG:Nd laser are substantiated theoretically.

Multi-channel laser system with phase locking by holographic gain gratings and small diameter deep hole drilling

A phase-locked three-channel Nd:YAG laser system based on phase-conjugate loop oscillators is designed and studied. The Nd:YAG laser system had three laser outputs as the self-Q-switched laser 100-mJ monopulses interfering with an interference pattern contrast tending to unity giving a sixfold interferential increase of the laser brightness. A new opportunity to apply the Nd:YAG laser systems based on phase-conjugate loop oscillators for drilling of the super-deep (up to 27 mm deep) holes of small 100-micron diameter for the most perspective metals, alloys and ceramics with different composition is shown.

Self-starting 100-W-average-power laser with a self-adaptive cavity

The numerical and experimental investigation of a self- starting Nd:YAG laser oscillator with a cavity completed by population gratings induced in the laser crystal by generating beams themselves are reported. The spatio- temporal characteristics of the laser comprising three Nd:YAG amplifiers and a saturable absorber were investigated. The generation of single mode beam with an average power of as large as 100 W and high quality was achieved.

Economic technology of laser cutting

The laser cutting of color metals and alloys by a thickness more than 2 mm has significant difficulties due to high reflective ability and large thermal conduction. We made it possible to raise energy efficiency and quality of laser cutting by using a laser processing system (LPS) consisting both of the YAG:Nd laser with passive Q-switching on base of LiF:F2- crystals and the CO2 laser. A distinctive feature of the LPS is that the radiation of different lasers incorporated in a coaxial beam has simultaneously high level of peak power (more than 400 kW in a TEM00 mode) and significant level of average power (up to 800 W in a TEM01 mode of the CO2 laser). The application of combined radiation for cutting of an aluminum alloy of D16 type made it possible to decrease the cutting energy threshold in 1.7 times, to increase depth of treatment from 2 up to 4 mm, and velocity from 0.015 up to 0.7 m/min, and also to eliminate application of absorptive coatings. At cutting of steels the velocity of treatment was doubled, and also an oxygen flow was eliminated from the technological process and replaced by the air. The obtained raise of energy efficiency and quality of cutting is explained by an essential size reducing of a formed penetration channel and by the shifting of a thermal cutting mode from melting to evaporation. The evaluation of interaction efficiency of a combined radiation was produced on the basis of non-stationary thermal-hydrodynamic model of a heating source moving as in the cutting direction, and also into the depth of material.

Single-mode Nd:YAG laser with cavity formed by population gratings

Q-switched regimes of the nanosecond pulse-periodic Nd:YAG laser with dynamic cavity formed with participation of dynamics holographic gratings in laser elements have been investigated. A Sagnac interferometer was applied as a laser cavity mirror for angular selection of initial radiation. As a passive Q-switch, we used saturable absorber crystal LiF:F2-, which increased total intracavity diffraction efficiency of dynamic gratings completing the cavity. Self-pumped phase conjugation in Nd:YAG amplifier and LiF:F2- absorber provided adaptive properties of the cavity. The peak power of generated beam with diffraction quality exceeded 17.5 MW and the average power achieved 50 W.

Mathematical modeling of the thermal and optical parameters of the zone of laser influence for determining the feedback parameters for a system of adaptive precision laser material processing

We develop a mathematical model of channel formation in the ablation regime at the initial non-stationary stage of growth that establishes the relationship between channel parameters such as temperature, optical parameters of the irradiated surface and erosion flow, and the parameters of laser action. The solution to a two-dimensional heat equation, coordinated with the solution to the problem of propagation of an ablation front and the formation of flows of evaporated material and plasma, is found in a grid with variable boundaries.

Phase Locking Control of the Multichannel Holographic Laser System with the Help of Passive Q-Switch

Method of phase-locking control of the multichannel laser system by use of a passive Q-switch is proposed. For the first time a phase-locked and Q-switched oscillation of the multichannel Nd:YAG-laser system is realized.