Svetlana Ivanova - Academia.edu (original) (raw)

Papers by Svetlana Ivanova

Research paper thumbnail of Calculations of the transitions intensities in the optical spectra of Dy< sup> 3+</sup>: LiYF< sub> 4</sub>

Journal of Alloys and Compounds

Optical spectra of Dy 3+ :LiYF 4 (Dy 3+ :YLF) single crystal were analyzed using Judd-Ofelt theor... more Optical spectra of Dy 3+ :LiYF 4 (Dy 3+ :YLF) single crystal were analyzed using Judd-Ofelt theory and discrete variational multielectron method (DVME). Oscillator strengths (OS) of transitions up to 39 000 cm −1 in the absorption spectrum, branching ratios and nonradiative transition rates were calculated; assignment of the absorption transitions was given. A good agreement between calculated and experimental values of branching ratios for transitions from quartet 4 F (3) 9/2 to the low-lying sextet levels is demonstrated. Ab initio calculations of OS were performed.

Research paper thumbnail of Spectroscopic studies of Dy3 + :YLF crystals

Research paper thumbnail of Spectroscopic study of Dy3+- and Yb3+-doped double chloride and double fluoride crystals for telecommunication amplifiers and IR lasers

Proceedings of SPIE - The International Society for Optical Engineering

In this work we studied the optical spectra of dysprosium and ytterbium doped double chloride MeP... more In this work we studied the optical spectra of dysprosium and ytterbium doped double chloride MePb2Cl5:RE3+ (Me equals K, Rb), and double fluoride LiYF4:RE3+ (RE3+ equals Dy, Yb) crystals. RE3+ doped double chloride and double fluoride crystals have been grown, by using Bridgeman technique. Optical spectra were studied, intensity parameters are determined using Judd-Ofelt method and radiative probabilities and branching ratio were calculated. Yb3+ -Dy3+ energy transfer processes in KPb2Cl5:Dy3+,Yb3+ and LiYF4:Dy3+,Yb3+ were considered.

Research paper thumbnail of Spectroscopic study of Na/sub 0.4/Y/sub 0.6/F/sub 22/:Nd/sup 3+/ crystals

form only given. Summary from only given. Compact upconversion pumped solid state lasers are one ... more form only given. Summary from only given. Compact upconversion pumped solid state lasers are one of the most active areas of laser research and development today. The efficiency of upconversion mechanisms was successfully demonstrated on a number of rare earth doped crystals with metastable levels including Nd-doped laser crystals.

Research paper thumbnail of Spectroscopic study of Na0.4Y0.6F22:Nd3+ crystals

Filtration Industry Analyst

Summary from only given. Compact upconversion pumped solid state lasers are one of the most activ... more Summary from only given. Compact upconversion pumped solid state lasers are one of the most active areas of laser research and development today. The efficiency of upconversion mechanisms was successfully demonstrated on a number of rare earth doped crystals with metastable levels including Nd-doped laser crystals

Research paper thumbnail of Luminescence self-quenching in praseodymium-doped double sodium-yttrium fluoride cubic crystals (Na0.4Y0.6F2.2:Pr3+)

Optics and Spectroscopy, 2015

ABSTRACT Energy transfer processes between praseodymium dopant ions, which are responsible for th... more ABSTRACT Energy transfer processes between praseodymium dopant ions, which are responsible for the luminescence self-quenching in crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+; Pr = 0.4-9%), have been investigated experimentally and theoretically. Using methods of kinetic spectroscopy with selective excitation, the praseodymium luminescence decay kinetics from the levels 3 P 0,1 and 1 D 2 selectively excited by nanosecond laser pulses has been studied. Based on model quantum-mechanical calculations, interionic interaction microparameters have been determined theoretically and mechanisms that are responsible for the interaction of praseodymium ions by particular most likely energy transfer schemes have been elucidated. Energy transfer macrorates (of migration and quenching) have been found, and the values obtained have been used as parameters for calculation of the decay dynamics of the excited 1 D 2 and 3 P 0,1 levels of praseodymium ions. It has been shown that luminescence self-quenching from the 1 D 2 level in NYF:Pr3+ crystals can be described well in terms of the model of static ordered decay in the presence of dipole-dipole and dipole-quadrupole interactions. The luminescence self-quenching from the 3 P 0,1 levels is mainly determined by the dipole-dipole interaction, and it also can be described in terms of the model of the static ordered decay. Good agreement has been obtained between experimental and calculated kinetic dependences that characterize energy transfer processes in NYF:Pr3+ crystals in relation to the concentration of doping ions. Based on the obtained data, it has been concluded that investigated crystals of a certain composition are promising for use in quantum electronics and optical converters.

Research paper thumbnail of State-Related Activity, Reactivity of Locus Ceruleus Neurons in Behaving Monkeys

Advances in Pharmacology, 1997

Research paper thumbnail of ChemInform Abstract: Fluorination of B10H2-10 with an N-Fluoro Reagent. A New Way to Transform B-H Bonds into B-F Bonds

Research paper thumbnail of Up-conversion processes and population dynamics of excited levels in Er/sup 3+/ doped KPb/sub 2/Cl/sub 5/ crystals as new potential VIS and IR laser material

2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666), 2003

ABSTRACT In this paper, optical spectra, luminescence decays and up-conversion processes in Er3+:... more ABSTRACT In this paper, optical spectra, luminescence decays and up-conversion processes in Er3+: KPb2Cl5 crystals, grown by Bridgman technique were studied. The luminescence spectra were recorded under UV and LD excitation, intensity parameters were determined by Judd-Ofelt method; radiative and radiationless transition probabilities were calculated. Luminescence kinetics from excited Er3+ levels, studied under its selective laser excitation, concentration quenching and up conversion processes, were considered. The conclusion is made that the Er3+:KPC crystals can be considered as one of the most promising active media for VIS and IR solid-state up-conversion LD pumped lasers with extremely low Stocks&#39; losses.

Research paper thumbnail of New materials for UV, VIS and mid-IR solid state lasers based on the rare earth doped double chloride crystals (TR/sup 3+/:KPb/sub 2/Cl/sub 5/)

2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666), 2003

ABSTRACT Laser action of the TR:KPC (KPb2Cl5) crystals was achieved with Dy at 2.4 μm. In the pre... more ABSTRACT Laser action of the TR:KPC (KPb2Cl5) crystals was achieved with Dy at 2.4 μm. In the present work we continued studying this new systems based on TR3+ doped chloride matrix suitable for diode-pumped lasers. We studied the optical spectra and luminescence kinetics, calculated radiative and nonradiative transition probabilities, considered up-conversion processes and possibility of energy transfer from exciton matrix band to TR3+ ions. Intensive absorption band in UV spectral range (λ

Research paper thumbnail of Energy Transfer and Population of 4S3/2 and 4F9/2 Erbium Levels in Er3+:Na0.4Y0.6F2.2 Laser Crystals under Direct and Upconversion Selective IR Excitation

Advanced Solid-State Photonics, 2005

ABSTRACT Energy transfer processes in Er3+:Na0.4Y0.6F2.2 laser crystals under selective laser dio... more ABSTRACT Energy transfer processes in Er3+:Na0.4Y0.6F2.2 laser crystals under selective laser diode pumping have been studied theoretically and experimentally. Concentration and pump power dependences of the intensity of luminescence from the 4S3/2 and 4F9/2 levels are investigated. It is shown, that under LD excitation at 4I11/2 level (?exc= 975 nm) and certain conditions of pumping and erbium concentration the 4F9/2 level is populated due to complicated excitation pathway including ESA from 4I11/2 and 4I13/2 levels and upconversion energy transfer steps, while relaxation from the 4S3/2 level is ineffective for population of the 4F9/2 level. The relative intensity of red (4F9/2 level) and green (4S3/2 level) luminescence can be controlled by means of excitation power, doping concentration and temperature.

Research paper thumbnail of Emission Peculiarities of TR3+-Doped KPb2Cl5 Laser Crystals under Selective Direct, Upconversion and Excitonic/Host Excitation of Impurity Centers

Advanced Solid-State Photonics, 2005

... Ivanova SI Vavilov State Optical Institute, St. Petersburg, 199034, Russia. tkachuk@mail.rcom... more ... Ivanova SI Vavilov State Optical Institute, St. Petersburg, 199034, Russia. tkachuk@mail.rcom. ru LI Isaenko and AP Yelisseyev Institute of Mineralogy & Petrography SB RAS, Russkaya str. 43, Novosibirsk, 630058, Russia VA Pustovarov Urals State Technical University, Mira ...

Research paper thumbnail of Spectroscopic properties of TR3+-doped double chloride crystals

ABSTRACT We studied the optical spectra and luminescence kinetics of double chloride Kpb2Cl5:TR3+... more ABSTRACT We studied the optical spectra and luminescence kinetics of double chloride Kpb2Cl5:TR3+ crystals as a new luminescent material promising for UV, VIS and mid-IR lasers, pumped with laser diodes. Intensity parameters were determined by the Judd-Ofelt method, radiative and non- radiative transition probabilities were calculated. It is shown that low multiphoton relaxation rate in the se crystal together with high values of radiative probabilities leads to the evidence of high intensive luminescence in spectral domain from 360 to 5000 nm. These features make these crystals promising for practical applications as active media for UV, VIS and mid-IR solid state lasers and amplifiers.

Research paper thumbnail of Spectroscopic characteristics of Pr-doped Na<inf>0.4</inf>Y<inf>0.6</inf>F<inf>2.2</inf> crystals, promising for lasing in near IR and visible range

2014 International Conference Laser Optics, 2014

ABSTRACT Spectroscopic characteristics of intracenter transitions in disordered crystals of sodiu... more ABSTRACT Spectroscopic characteristics of intracenter transitions in disordered crystals of sodium-yttrium double fluoride Na0.4Y0.6F2.2: Pr3+ with cubic structure, grown by Stockbarger-Bridgeman method, are investigated theoretically and experimentally in order to evaluate their potential for application as active media of solid state lasers emitting in visible spectral range.

Research paper thumbnail of Spectroscopic characterization of Tm-doped sodium-yttrium double fluoride crystals for LD – pumped tuneable IR lasers

CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009

In this work, we report on spectroscopic study of Tm3+ doped NYF (Tm:NYF) crystals, including ene... more In this work, we report on spectroscopic study of Tm3+ doped NYF (Tm:NYF) crystals, including energy transfer processes, in order to evaluate their potential for application as an active media of solid state tunable diode-pumped lasers.

Research paper thumbnail of <title>New low-phonon frequency crystals based on rare-earth-doped double halogenides for multiwavelength diode-pumped solid state lasers</title>

Seventh International Symposium on Laser Metrology Applied to Science,Industry, and Everyday Life, 2002

ABSTRACT Energy (frequency) of phonons is the main parameter which determines ratio between proba... more ABSTRACT Energy (frequency) of phonons is the main parameter which determines ratio between probabilities of radiative and radiationless transitions in luminescence. Single crystals of double chlorides KPb2Cl5 and bromides KPb2Br5, which are formed by heavy ions and have a low energy phonon spectrum (homega(max) &lt; 200 and 150 cm(-1) respectively), of optical quality were obtained using the Bridgmen-Stockbarger technique. We studied the optical spectra and luminescence kinetics of RE -doped crystals (RE= Pr3+, Nd3+, Tb3+, Ho3+, Er3+ etc). Intensity parameters were determined by the Judd-Ofelt method, radiative and non-radiative transition probabilities were calculated. It was shown that low multiphonon relaxation rate in these crystals together with high values of radiative probabilities leads to the evidence of high intensity luminescence in spectral domain from 360 to 9000 nm. These features make these crystals promising for practical applications as active media for UV, VIS and mid-IR solid state lasers and amplifiers with laser diode pumping.

Research paper thumbnail of Luminescence and laser action of Nd3+ doped double chloride crystal

Filtration Industry Analyst, 2000

Summary form only given. The low-energy phonon spectrum of chloride crystals allows rare-earth io... more Summary form only given. The low-energy phonon spectrum of chloride crystals allows rare-earth ions to serve as favorable luminescent centers for laser action in the IR spectral region, whereas the luminescence of fluoride and oxide crystals is quenched by fast multiphonon relaxation. We have searched for a crystalline chloride matrix suitable for diode-pumped lasers. The knowledge of radiative probabilities of

Research paper thumbnail of Dy3+-doped crystals of double chlorides and double fluorides as the active media of IR solid-state lasers and telecommunication amplifiers

Journal of Optical Technology, 1999

A comparative spectroscopic study of Dy 3ϩ -doped crystals of double chlorides KPb 2 Cl 5 :Dy 3ϩ ... more A comparative spectroscopic study of Dy 3ϩ -doped crystals of double chlorides KPb 2 Cl 5 :Dy 3ϩ and double fluorides LiYF 4 :Dy 3ϩ grown by the Bridgman-Stockbarger method has been carried out. The spectra of the absorption cross sections have been studied, and the Judd-Ofelt method has been used to determine the intensity parameters. On the basis of estimates of the probabilities of radiative and nonradiative transitions in the dysprosium ion and an experimental study of the luminescence spectra, it has been concluded that YLF:Dy 3ϩ and YLF:Dy 3ϩ , Yb 3ϩ crystals can be regarded as promising active media for 3-m lasers with diode pumping and that KPb 2 Cl 5 :Dy 3ϩ and KPb 2 Cl 5 :Dy 3ϩ , Yb 3ϩ crystals are unique in the number of radiative transitions in the dysprosium ion, including the IR region of the spectrum, all the way to 4 m. The effect of amplification at a wavelength of 1.319 m obtained in them indicates that they can be used in practice as new active media in telecommunication amplifiers and lasers.

Research paper thumbnail of Some problems of optimizing shell shape and thickness distribution on the basis of a genetic algorithm

Mechanics of Solids, 2007

ABSTRACT We consider problems related to designing axisymmetric shells of minimal weight (mass) a... more ABSTRACT We consider problems related to designing axisymmetric shells of minimal weight (mass) and the development of efficient nonlocal optimization methods. The optimization problems under study consist in simultaneous search for the optimal geometry and the shell thickness optimal distribution from the minimal weight condition under strength constraints and additional geometric constraints imposed on the thickness function, the transverse cross-section radii distribution, and the volume enclosed by the shell. Using the method of penalty functions, we reduce the above optimal design problem to a nonconvex minimization problem for the extended Lagrange functional. To find the global optimum, we apply an efficient genetic algorithm. We present the results of numerical solution of the optimal design problem for dome-like shells of revolution under the action of gravity forces. We present some data characterizing the convergence of the method developed here.

Research paper thumbnail of On the penetration of nonaxisymmetric bodies into a deformable solid medium and their shape optimization

Mechanics of Solids, 2008

ABSTRACT We consider the problem of penetration of rigid pyramidal bodies (impactors) into a stra... more ABSTRACT We consider the problem of penetration of rigid pyramidal bodies (impactors) into a strained medium in the case of large speeds of penetration and estimate the depth of the impactor penetration. To this end, we use the two-stage penetration model proposed by Forrestall. We state the shape optimization problem for the penetrating body, which is based on the consideration of a set of bodies of pyramidal external shape with given fixed mass. We study both solid and hollow (shell-shaped) bodies. For the optimization functional we take the penetration depth of the penetrating body, and for the projection variable we take the number of faces of the pyramidal body. We present the results of computations of the penetration depth for different shapes of the impactor and show that, both for shells and solid impactors, the bodies of the shape of a circular cone are optimal. The problems of high-speed penetration of rigid bodies into a deformable medium are nowadays very topical problems [1] which have been studied by Russian and foreign authors [2–8].

Research paper thumbnail of Calculations of the transitions intensities in the optical spectra of Dy< sup> 3+</sup>: LiYF< sub> 4</sub>

Journal of Alloys and Compounds

Optical spectra of Dy 3+ :LiYF 4 (Dy 3+ :YLF) single crystal were analyzed using Judd-Ofelt theor... more Optical spectra of Dy 3+ :LiYF 4 (Dy 3+ :YLF) single crystal were analyzed using Judd-Ofelt theory and discrete variational multielectron method (DVME). Oscillator strengths (OS) of transitions up to 39 000 cm −1 in the absorption spectrum, branching ratios and nonradiative transition rates were calculated; assignment of the absorption transitions was given. A good agreement between calculated and experimental values of branching ratios for transitions from quartet 4 F (3) 9/2 to the low-lying sextet levels is demonstrated. Ab initio calculations of OS were performed.

Research paper thumbnail of Spectroscopic studies of Dy3 + :YLF crystals

Research paper thumbnail of Spectroscopic study of Dy3+- and Yb3+-doped double chloride and double fluoride crystals for telecommunication amplifiers and IR lasers

Proceedings of SPIE - The International Society for Optical Engineering

In this work we studied the optical spectra of dysprosium and ytterbium doped double chloride MeP... more In this work we studied the optical spectra of dysprosium and ytterbium doped double chloride MePb2Cl5:RE3+ (Me equals K, Rb), and double fluoride LiYF4:RE3+ (RE3+ equals Dy, Yb) crystals. RE3+ doped double chloride and double fluoride crystals have been grown, by using Bridgeman technique. Optical spectra were studied, intensity parameters are determined using Judd-Ofelt method and radiative probabilities and branching ratio were calculated. Yb3+ -Dy3+ energy transfer processes in KPb2Cl5:Dy3+,Yb3+ and LiYF4:Dy3+,Yb3+ were considered.

Research paper thumbnail of Spectroscopic study of Na/sub 0.4/Y/sub 0.6/F/sub 22/:Nd/sup 3+/ crystals

form only given. Summary from only given. Compact upconversion pumped solid state lasers are one ... more form only given. Summary from only given. Compact upconversion pumped solid state lasers are one of the most active areas of laser research and development today. The efficiency of upconversion mechanisms was successfully demonstrated on a number of rare earth doped crystals with metastable levels including Nd-doped laser crystals.

Research paper thumbnail of Spectroscopic study of Na0.4Y0.6F22:Nd3+ crystals

Filtration Industry Analyst

Summary from only given. Compact upconversion pumped solid state lasers are one of the most activ... more Summary from only given. Compact upconversion pumped solid state lasers are one of the most active areas of laser research and development today. The efficiency of upconversion mechanisms was successfully demonstrated on a number of rare earth doped crystals with metastable levels including Nd-doped laser crystals

Research paper thumbnail of Luminescence self-quenching in praseodymium-doped double sodium-yttrium fluoride cubic crystals (Na0.4Y0.6F2.2:Pr3+)

Optics and Spectroscopy, 2015

ABSTRACT Energy transfer processes between praseodymium dopant ions, which are responsible for th... more ABSTRACT Energy transfer processes between praseodymium dopant ions, which are responsible for the luminescence self-quenching in crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+; Pr = 0.4-9%), have been investigated experimentally and theoretically. Using methods of kinetic spectroscopy with selective excitation, the praseodymium luminescence decay kinetics from the levels 3 P 0,1 and 1 D 2 selectively excited by nanosecond laser pulses has been studied. Based on model quantum-mechanical calculations, interionic interaction microparameters have been determined theoretically and mechanisms that are responsible for the interaction of praseodymium ions by particular most likely energy transfer schemes have been elucidated. Energy transfer macrorates (of migration and quenching) have been found, and the values obtained have been used as parameters for calculation of the decay dynamics of the excited 1 D 2 and 3 P 0,1 levels of praseodymium ions. It has been shown that luminescence self-quenching from the 1 D 2 level in NYF:Pr3+ crystals can be described well in terms of the model of static ordered decay in the presence of dipole-dipole and dipole-quadrupole interactions. The luminescence self-quenching from the 3 P 0,1 levels is mainly determined by the dipole-dipole interaction, and it also can be described in terms of the model of the static ordered decay. Good agreement has been obtained between experimental and calculated kinetic dependences that characterize energy transfer processes in NYF:Pr3+ crystals in relation to the concentration of doping ions. Based on the obtained data, it has been concluded that investigated crystals of a certain composition are promising for use in quantum electronics and optical converters.

Research paper thumbnail of State-Related Activity, Reactivity of Locus Ceruleus Neurons in Behaving Monkeys

Advances in Pharmacology, 1997

Research paper thumbnail of ChemInform Abstract: Fluorination of B10H2-10 with an N-Fluoro Reagent. A New Way to Transform B-H Bonds into B-F Bonds

Research paper thumbnail of Up-conversion processes and population dynamics of excited levels in Er/sup 3+/ doped KPb/sub 2/Cl/sub 5/ crystals as new potential VIS and IR laser material

2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666), 2003

ABSTRACT In this paper, optical spectra, luminescence decays and up-conversion processes in Er3+:... more ABSTRACT In this paper, optical spectra, luminescence decays and up-conversion processes in Er3+: KPb2Cl5 crystals, grown by Bridgman technique were studied. The luminescence spectra were recorded under UV and LD excitation, intensity parameters were determined by Judd-Ofelt method; radiative and radiationless transition probabilities were calculated. Luminescence kinetics from excited Er3+ levels, studied under its selective laser excitation, concentration quenching and up conversion processes, were considered. The conclusion is made that the Er3+:KPC crystals can be considered as one of the most promising active media for VIS and IR solid-state up-conversion LD pumped lasers with extremely low Stocks&#39; losses.

Research paper thumbnail of New materials for UV, VIS and mid-IR solid state lasers based on the rare earth doped double chloride crystals (TR/sup 3+/:KPb/sub 2/Cl/sub 5/)

2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666), 2003

ABSTRACT Laser action of the TR:KPC (KPb2Cl5) crystals was achieved with Dy at 2.4 μm. In the pre... more ABSTRACT Laser action of the TR:KPC (KPb2Cl5) crystals was achieved with Dy at 2.4 μm. In the present work we continued studying this new systems based on TR3+ doped chloride matrix suitable for diode-pumped lasers. We studied the optical spectra and luminescence kinetics, calculated radiative and nonradiative transition probabilities, considered up-conversion processes and possibility of energy transfer from exciton matrix band to TR3+ ions. Intensive absorption band in UV spectral range (λ

Research paper thumbnail of Energy Transfer and Population of 4S3/2 and 4F9/2 Erbium Levels in Er3+:Na0.4Y0.6F2.2 Laser Crystals under Direct and Upconversion Selective IR Excitation

Advanced Solid-State Photonics, 2005

ABSTRACT Energy transfer processes in Er3+:Na0.4Y0.6F2.2 laser crystals under selective laser dio... more ABSTRACT Energy transfer processes in Er3+:Na0.4Y0.6F2.2 laser crystals under selective laser diode pumping have been studied theoretically and experimentally. Concentration and pump power dependences of the intensity of luminescence from the 4S3/2 and 4F9/2 levels are investigated. It is shown, that under LD excitation at 4I11/2 level (?exc= 975 nm) and certain conditions of pumping and erbium concentration the 4F9/2 level is populated due to complicated excitation pathway including ESA from 4I11/2 and 4I13/2 levels and upconversion energy transfer steps, while relaxation from the 4S3/2 level is ineffective for population of the 4F9/2 level. The relative intensity of red (4F9/2 level) and green (4S3/2 level) luminescence can be controlled by means of excitation power, doping concentration and temperature.

Research paper thumbnail of Emission Peculiarities of TR3+-Doped KPb2Cl5 Laser Crystals under Selective Direct, Upconversion and Excitonic/Host Excitation of Impurity Centers

Advanced Solid-State Photonics, 2005

... Ivanova SI Vavilov State Optical Institute, St. Petersburg, 199034, Russia. tkachuk@mail.rcom... more ... Ivanova SI Vavilov State Optical Institute, St. Petersburg, 199034, Russia. tkachuk@mail.rcom. ru LI Isaenko and AP Yelisseyev Institute of Mineralogy & Petrography SB RAS, Russkaya str. 43, Novosibirsk, 630058, Russia VA Pustovarov Urals State Technical University, Mira ...

Research paper thumbnail of Spectroscopic properties of TR3+-doped double chloride crystals

ABSTRACT We studied the optical spectra and luminescence kinetics of double chloride Kpb2Cl5:TR3+... more ABSTRACT We studied the optical spectra and luminescence kinetics of double chloride Kpb2Cl5:TR3+ crystals as a new luminescent material promising for UV, VIS and mid-IR lasers, pumped with laser diodes. Intensity parameters were determined by the Judd-Ofelt method, radiative and non- radiative transition probabilities were calculated. It is shown that low multiphoton relaxation rate in the se crystal together with high values of radiative probabilities leads to the evidence of high intensive luminescence in spectral domain from 360 to 5000 nm. These features make these crystals promising for practical applications as active media for UV, VIS and mid-IR solid state lasers and amplifiers.

Research paper thumbnail of Spectroscopic characteristics of Pr-doped Na<inf>0.4</inf>Y<inf>0.6</inf>F<inf>2.2</inf> crystals, promising for lasing in near IR and visible range

2014 International Conference Laser Optics, 2014

ABSTRACT Spectroscopic characteristics of intracenter transitions in disordered crystals of sodiu... more ABSTRACT Spectroscopic characteristics of intracenter transitions in disordered crystals of sodium-yttrium double fluoride Na0.4Y0.6F2.2: Pr3+ with cubic structure, grown by Stockbarger-Bridgeman method, are investigated theoretically and experimentally in order to evaluate their potential for application as active media of solid state lasers emitting in visible spectral range.

Research paper thumbnail of Spectroscopic characterization of Tm-doped sodium-yttrium double fluoride crystals for LD – pumped tuneable IR lasers

CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009

In this work, we report on spectroscopic study of Tm3+ doped NYF (Tm:NYF) crystals, including ene... more In this work, we report on spectroscopic study of Tm3+ doped NYF (Tm:NYF) crystals, including energy transfer processes, in order to evaluate their potential for application as an active media of solid state tunable diode-pumped lasers.

Research paper thumbnail of <title>New low-phonon frequency crystals based on rare-earth-doped double halogenides for multiwavelength diode-pumped solid state lasers</title>

Seventh International Symposium on Laser Metrology Applied to Science,Industry, and Everyday Life, 2002

ABSTRACT Energy (frequency) of phonons is the main parameter which determines ratio between proba... more ABSTRACT Energy (frequency) of phonons is the main parameter which determines ratio between probabilities of radiative and radiationless transitions in luminescence. Single crystals of double chlorides KPb2Cl5 and bromides KPb2Br5, which are formed by heavy ions and have a low energy phonon spectrum (homega(max) &lt; 200 and 150 cm(-1) respectively), of optical quality were obtained using the Bridgmen-Stockbarger technique. We studied the optical spectra and luminescence kinetics of RE -doped crystals (RE= Pr3+, Nd3+, Tb3+, Ho3+, Er3+ etc). Intensity parameters were determined by the Judd-Ofelt method, radiative and non-radiative transition probabilities were calculated. It was shown that low multiphonon relaxation rate in these crystals together with high values of radiative probabilities leads to the evidence of high intensity luminescence in spectral domain from 360 to 9000 nm. These features make these crystals promising for practical applications as active media for UV, VIS and mid-IR solid state lasers and amplifiers with laser diode pumping.

Research paper thumbnail of Luminescence and laser action of Nd3+ doped double chloride crystal

Filtration Industry Analyst, 2000

Summary form only given. The low-energy phonon spectrum of chloride crystals allows rare-earth io... more Summary form only given. The low-energy phonon spectrum of chloride crystals allows rare-earth ions to serve as favorable luminescent centers for laser action in the IR spectral region, whereas the luminescence of fluoride and oxide crystals is quenched by fast multiphonon relaxation. We have searched for a crystalline chloride matrix suitable for diode-pumped lasers. The knowledge of radiative probabilities of

Research paper thumbnail of Dy3+-doped crystals of double chlorides and double fluorides as the active media of IR solid-state lasers and telecommunication amplifiers

Journal of Optical Technology, 1999

A comparative spectroscopic study of Dy 3ϩ -doped crystals of double chlorides KPb 2 Cl 5 :Dy 3ϩ ... more A comparative spectroscopic study of Dy 3ϩ -doped crystals of double chlorides KPb 2 Cl 5 :Dy 3ϩ and double fluorides LiYF 4 :Dy 3ϩ grown by the Bridgman-Stockbarger method has been carried out. The spectra of the absorption cross sections have been studied, and the Judd-Ofelt method has been used to determine the intensity parameters. On the basis of estimates of the probabilities of radiative and nonradiative transitions in the dysprosium ion and an experimental study of the luminescence spectra, it has been concluded that YLF:Dy 3ϩ and YLF:Dy 3ϩ , Yb 3ϩ crystals can be regarded as promising active media for 3-m lasers with diode pumping and that KPb 2 Cl 5 :Dy 3ϩ and KPb 2 Cl 5 :Dy 3ϩ , Yb 3ϩ crystals are unique in the number of radiative transitions in the dysprosium ion, including the IR region of the spectrum, all the way to 4 m. The effect of amplification at a wavelength of 1.319 m obtained in them indicates that they can be used in practice as new active media in telecommunication amplifiers and lasers.

Research paper thumbnail of Some problems of optimizing shell shape and thickness distribution on the basis of a genetic algorithm

Mechanics of Solids, 2007

ABSTRACT We consider problems related to designing axisymmetric shells of minimal weight (mass) a... more ABSTRACT We consider problems related to designing axisymmetric shells of minimal weight (mass) and the development of efficient nonlocal optimization methods. The optimization problems under study consist in simultaneous search for the optimal geometry and the shell thickness optimal distribution from the minimal weight condition under strength constraints and additional geometric constraints imposed on the thickness function, the transverse cross-section radii distribution, and the volume enclosed by the shell. Using the method of penalty functions, we reduce the above optimal design problem to a nonconvex minimization problem for the extended Lagrange functional. To find the global optimum, we apply an efficient genetic algorithm. We present the results of numerical solution of the optimal design problem for dome-like shells of revolution under the action of gravity forces. We present some data characterizing the convergence of the method developed here.

Research paper thumbnail of On the penetration of nonaxisymmetric bodies into a deformable solid medium and their shape optimization

Mechanics of Solids, 2008

ABSTRACT We consider the problem of penetration of rigid pyramidal bodies (impactors) into a stra... more ABSTRACT We consider the problem of penetration of rigid pyramidal bodies (impactors) into a strained medium in the case of large speeds of penetration and estimate the depth of the impactor penetration. To this end, we use the two-stage penetration model proposed by Forrestall. We state the shape optimization problem for the penetrating body, which is based on the consideration of a set of bodies of pyramidal external shape with given fixed mass. We study both solid and hollow (shell-shaped) bodies. For the optimization functional we take the penetration depth of the penetrating body, and for the projection variable we take the number of faces of the pyramidal body. We present the results of computations of the penetration depth for different shapes of the impactor and show that, both for shells and solid impactors, the bodies of the shape of a circular cone are optimal. The problems of high-speed penetration of rigid bodies into a deformable medium are nowadays very topical problems [1] which have been studied by Russian and foreign authors [2–8].