Engineering topics

Palashov, O V

Publications and source records attributed to Palashov, O V.

16 records

DOE OSTI2016

Investigation of lasing characteristics of domestic Yb : YAG laser ceramics

We report on the synthesis and laser characteristics of Yb{sup 3+}-doped yttrium aluminium garnet (Y{sub 3}Al{sub 5}O{sub 12}) optical ceramics. The ceramics was produced by solid-phase reactive sintering of a mixture of Yb (5 at %) : Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} nanopowders synthesised by laser ablation, using additional calcination of the mixture before compaction. In a thin disk geometry, multiwatt laser oscillation was obtained at a wavelength of 1030 nm with a power of 5.2 W and a slope efficiency of 37.0% at a pump pulse period-toduration ratio of 5.72. (lasers)

36 MATERIALS SCIENCE↗

DOE OSTI2016

Yb : YAG thin-rod laser amplifier with a high pulse energy for a fibre oscillator

High (more than ten times) small-signal gain is demonstrated in an Yb : YAG single crystal thin rods with pumping by a fibre-coupled diode laser. A four-pass amplifier for a fibre master oscillator with an average output power exceeding 15 W at a pulse repetition rate of 3 MHz is fabricated based on this active element. The small-signal gain in the developed amplifier is 26 dB, which is comparable with the gain in regenerative amplifiers. The possibility of obtaining sub-millijoule pulse energy at a pulse repetition rate of tens of kilohertz is shown. (extreme laser radiation: physics and fundamental applications)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2016

Comparative characteristics of Yb:(YLa){sub 2}O{sub 3} laser ceramics

Two samples of laser ceramics synthesised at Russian institutes by two different methods are studied. The optical quality of the samples is measured, and efficient (36.6%) lasing in one of the samples is obtained under pumping at a wavelength of 940 nm. (lasers)

36 MATERIALS SCIENCE↗

DOE OSTI2015

Front-end system for Yb : YAG cryogenic disk laser

A new front-end system for a cryogenic Yb : YAG laser is designed. The system consists of a femtosecond source, a stretcher and a regenerative amplifier with an output energy of 25 μJ at a pulse repetition rate of 49 kHz, a pulse duration of ∼2 ns and a bandwidth of ∼1.5 nm. After increasing the pump power of the regenerative amplifier, it is expected to achieve a pulse energy of ∼1 mJ at the input to cryogenic amplification stages, which will allow one to obtain laser pulses with a duration of several picoseconds at the output of the cryogenic laser after compression. (extreme light fields and their applications)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Thin-disk laser based on an Yb:YAG / YAG composite active element

A thin-disk laser module based on an Yb:YAG / YAG composite active element is developed with a small-signal gain of 1.25 and a stored energy of 400 mJ under cw pumping. The gain and thermally induced phase distortions in the module are studied experimentally. Based on this module, a thin-disk laser with an average power of 300 W and a slope efficiency of 42% is designed. (lasers)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Efficient lasing in Yb:(YLa){sub 2}O{sub 3} ceramics

A high-optical-quality sample of Yb{sub 0.1}Y{sub 1.7}La{sub 0.2}O{sub 3} ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate – nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%. (lasers)

36 MATERIALS SCIENCE↗

DOE OSTI2014

Nanosecond cryogenic Yb:YAG disk laser

A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ∼10{sup 8}. (lasers)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2013

Permanent-magnet Faraday isolator with the field intensity of 25 kOe

A Faraday isolator with a single magneto-optical element is constructed and experimentally tested. It provides the isolation ratio of 30 dB at an average laser radiation power of 650 W. These parameters are obtained by increasing the field intensity in the magnetic system of the isolator and employing a low-absorption magneto-optical element. (elements of laser devices)

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2013

Yb:(YLa){sub 2}O{sub 3} laser ceramics produced by microwave sintering

The possibility of using microwave heating for sintering of optical oxide ceramics and the advantages of this method are considered. Sintering of Yb{sub 0.1}:(YLa){sub 1.9}O{sub 3} ceramics by heating with 24-GHz radiation is studied. The compacts for sintering are prepared from nanosized powders obtained by high-temperature synthesis from acetate-nitrates of rare-earth metals. The effect of addition of lanthanum oxide and of the uniaxial pressing conditions on the microstructure and optical transmission of ceramics is studied. Lasing at a wavelength of 1030 nm with an efficiency of 7.5 % is achieved in ceramic samples of the (Yb{sub 0.05}Y{sub 0.1}La{sub 0.85}){sub 2}O{sub 3} composition under pumping by a laser diode at a wavelength of 940 nm. (extreme light fields and their applications)

36 MATERIALS SCIENCE↗

DOE OSTI2013

Calculation of the gain coefficient in cryogenically cooled Yb : YAG disks at high heat generation rates

We have calculated the stored energy and gain coefficient in disk gain elements cooled to cryogenic temperatures. The problem has been solved with allowance for intense heat generation, amplified spontaneous emission and parasitic lasing, without averaging over any spatial coordinate. The numerical simulation results agree well with experimental data, in particular at high heat generation rates. Experimental data and theoretical analysis indicate that composite disk gain elements containing an undoped region can store considerably more energy due to suppression of amplified spontaneous emission and parasitic lasing. (extreme light fields and their applications)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2013

Cryogenic disk Yb : YAG laser with 120-mJ energy at 500-Hz pulse repetition rate

A repetitively pulsed laser system based on cryogenically cooled Yb : YAG disks is developed. The creation of Yb : YAG/YAG composites and the use of an active liquid nitrogen cooling system made it possible to significantly decrease the effect of amplified spontaneous emission. The average output power of the system is 60 W. (extreme light fields and their applications)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Laser and thermal characteristics of Yb : YAG crystals in the 80 - 300 K temperature range

The spectral and thermooptical characteristics of an Yb : YAG crystal were measured in the 80 - 300 K temperature range. On cooling the crystal, the amplification cross section increases fivefold, the peak of the cross section spectrum shifts from 1030.1 to 1029.3 nm, and its width lowers from {approx}10 to 1.3 nm. These effects must be taken into account when operating with cryogenic amplifiers. Also measured were thermooptical constants P and Q as well as the photoelastic anisotropy parameter. These material constants completely determine the thermal and phase polarisation distortions in an active element when the heat release and the thermal conductivity coefficient are known. The thermoinduced depolarisation was shown to lower by a factor of 1000 and the optical strength by a factor of 50 on cooling the Yb : YAG crystal to a temperature of 78 K. (active media)

36 MATERIALS SCIENCE↗

DOE OSTI2011

Cooling and thermal stabilisation of Faraday rotators in the temperature range 300 - 200 K using Peltier elements

A new method for cooling and thermal stabilisation of Faraday rotators using Peltier elements is proposed and experimentally demonstrated. The scheme of thermal stabilisation of the magnetooptical elements ensures reliable operation of the device at the absorbed power {approx}2 W, which corresponds to the transmitted laser radiation power 1.5 kW. The results of the work make it possible to predict high efficiency of this method at the laser power of tens of kilowatts.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

Polarisation dynamics of a Nd:YAG ceramic laser

We report an experimental study of the polarisation dynamics of a dual-polarisation microchip Nd:YAG ceramic laser. Our results demonstrate dual-polarisation operation of the polycrystalline Nd:YAG laser. The low-frequency dynamics in this regime involves three types of relaxation oscillations, two of which are responsible for antiphase dynamics of the intensities of orthogonally polarised modes. Linearly polarised pump light induces gain anisotropy in the Nd:YAG ceramic, as in Nd:YAG single-crystal lasers. We present a comparative analysis of the behaviour of orthogonally polarised modes in Nd:YAG single-crystal lasers and the Nd:YAG ceramic laser, with a random orientation of the crystallographic axes in each grain (microcrystal), describe a technique for evaluating the total cavity loss from the relaxation oscillation spectrum and compare single-crystal and ceramic active elements. Experimental evidence is presented for gain anisotropy, loss anisotropy and phase anisotropy in ceramic and single-crystal microchip lasers. (lasers)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

Nonorthogonally magnetised permanent-magnet Faraday isolators

This paper describes a novel configuration of permanent-magnet magnetic systems for high-power Faraday isolators that are used in high-power lasers. An increase in magnetic field is ensured by magnets with a magnetisation vector inclined to the isolator axis. Numerical simulation results agree well with experimentally determined magnetic field distributions. (quantum electronic devices)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2010

Cryogenic Faraday isolator

A Faraday isolator is described in which thermal effects are suppressed by cooling down to liquid nitrogen temperatures. The principal scheme, main characteristics and modifications of the isolator are presented. The isolation degree is studied experimentally for the subkilowatt average laser radiation power. It is shown that the isolator can be used at radiation powers up to tens of kilowatts. (quantum electronic devices)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗