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Papers by Andrey Lipovskii

physica status solidi (b), 2012

Phone: þ358 13 251 5221, Fax: þ358 13 251 3290

Journal of Applied Physics, 2011

This paper concerns to rigorous analysis of the electrodiffusion problem arising during electric ... more This paper concerns to rigorous analysis of the electrodiffusion problem arising during electric field treatment of glasses and glass metal nanocomposites (e.g. glass poling effect). The strict solution of the carrier drift equations for two type ions differing in mobility and diffusion coefficient is obtained. This solution allows finding out the duration of space charge buildup and determining the limits of electroneutrality approximation. The rigorous solution demonstrates a good agreement with experimental data. The results of numerical solution are discussed as well.

Faraday Discuss., 2015

The paper is dedicated to the recently developed by the authors technique of silver nanoisland gr... more The paper is dedicated to the recently developed by the authors technique of silver nanoisland growth, allowing self-arrangement of 2D-patterns of nanoislands. The technique employs silver out-diffusion from ion-exchanged glass in the course of annealing in hydrogen. To modify the silver ion distribution in the exchanged soda-lime glass we included the thermal poling of the ion-exchanged glass with a profiled electrode as an intermediate stage of the process. The resulting consequence consists of three steps: (i) during the ion exchange of the glass in the AgxNa1-xNO3 (x = 0.01-0.15) melt we enrich the subsurface layer of the glass with silver ions; (ii) under the thermal poling, the electric field displaces these ions deeper into the glass under the 2D profiled anodic electrode, the displacement is smaller under the hollows in the electrode where the intensity of the field is minimal; (iii) annealing in a reducing atmosphere of hydrogen results in silver out-diffusion only in the regions corresponding to the electrode hollows, as a result silver forms nanoislands following the shape of the electrode. Varying the electrode and mode of processing allows governing the nanoisland size distribution and self-arrangement of the isolated single nanoislands, pairs, triples or groups of several nanoislands-so-called plasmonic molecules.

Materials that exhibit third-order nonlinear optical properties have an immense potential for pho... more Materials that exhibit third-order nonlinear optical properties have an immense potential for photonics applications [1]. In this case, it is important to characterize these materials by estimating the third-order nonlinear parameters, viz., two-photon absorption and nonlinear refractive index. In this case, different spectroscopic techniques such as wave mixing, Z-scan and energy scan are generally used to estimate the third-order coefficients [2]. Among the various classes of materials investigated, nonlinear optical glasses have been extensively studied as candidates for ultrafast optical switching (nonresonant nonlinearity) and optical power limiting (resonant nonlinearity). Concerning a resonant process, one of the most investigated high-order nonlinear optical phenomena is based on nonlinear (multi-photon) absorption. Optical power limiters based on nonlinear absorption rely on multi-step processes (reverse saturable absorption) and simultaneous absorption (hereafter called two-photon absorption). The major advantage of optical power limiters based on two-photon absorption is the instantaneous response to the excitation and large dynamic range, provided minimum linear absorption is present.

IEEE Journal of Selected Topics in Quantum Electronics, 2015

ABSTRACT

Technical Physics Letters, 2013

ABSTRACT Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by ... more ABSTRACT Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by selective etching and fixed to a silicon substrate by epoxy glue are studied using luminescence spectroscopy. A disc resonator 6 μm in diameter exhibits quasi-single-mode laser generation at a temperature of 78 K with a threshold power of 320 μW and λ/Δλ ˜ 27000.

Optical Engineering, 2000

A temperature fiber sensor based on CdSe-nanocrystallitedoped phosphate glass as a sensing elemen... more A temperature fiber sensor based on CdSe-nanocrystallitedoped phosphate glass as a sensing element is reported. This glass is shown to exhibit a reversible temperature-induced absorption edge shift at temperatures less than the annealing temperature of the glass (Ͻ370°C). A dual-wavelength detection scheme based on a reflective grating and bi-cell photodiode is employed to eliminate the effects of variable signal losses in the intensity-dependent sensor. A sensor prototype, tested in the temperature range of Ϫ20 to ϩ120°C, is shown to exhibit a linear response to temperature variations.

Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326), 2000

Physical Review B, 2001

Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass... more Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass by femtosecond pump-and-probe. The size dependence of the oscillation is investigated. Distinct low-frequency peaks are observed in Raman spectrum for the same samples. The size-dependence of the frequencies is well explained by elastic sphere model, but the observed modes are different to each other for coherent phonon and Raman scattering. Coherent phonon measurement and Raman scattering are found to give complementary information on confined acoustic phonons in this system.

Proceedings of SPIE - The International Society for Optical Engineering

ABSTRACT

Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS

We present results of using PbS-doped phosphate glass with the first excitonic peak at 1.3 μm as ... more We present results of using PbS-doped phosphate glass with the first excitonic peak at 1.3 μm as the saturable absorber for mode-locking of Nd:YAlO3, and Q-switching of Nd:YVO4 and Nd:KGd(WO4)2 lasers.

Glasses embedded with metal nanoclusters are prospective materials which can be used in optical r... more Glasses embedded with metal nanoclusters are prospective materials which can be used in optical recording and laser microfabrication . The conventional way to produce such nanoclusters in a glass consists in doping the glass by metals using ion exchange and subsequent reducing metallic ions to neutral metals . Annealing of metal-doped glasses in a hydrogen atmosphere leads to hydrogen diffusion accompanied by chemical reaction in the doped layer, in which metal ions are reduced to neutral state whereas neutral hydrogen atoms form OH groups and become ions. As solubility of neutral metal atoms in the glass matrix is negligible compared to the ion concentration in the doped layer, reduced metal atoms create high supersaturation in the glass matrix and form nanoclusters.

Technical Digest. Summaries of Papers Presented at the Conference on Lasers and Electro-Optics. Conference Edition. 1998 Technical Digest Series, Vol.6 (IEEE Cat. No.98CH36178), 1998

WEDNESDAY AFTERNOON / CLE0'98 / 251 the variation in y when the incident laser power was 7 W and ... more WEDNESDAY AFTERNOON / CLE0'98 / 251 the variation in y when the incident laser power was 7 W and ambient temperature was varied from 16.5 to 25°C. The oscillatory characteristics can be explained theoretically by considering the thermal expansion of LiNbO, and the difference between dn,/dT and dn,/ dT, where no and ne are the ordinary and extraordinary refractive indices of LiNbO, and T is the temperature, respectively. For this measurement, the angle between the EOM axis and incident polarization was purposely misaligned; for perfect alignment, the amplitude of this oscillatory behavior was reduced by more than two orders of magnitude. The same characteristics were observed in the whole range of laser power.

Defect and Diffusion Forum, 2005

Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag + ions leads to the reduc... more Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag + ions leads to the reduction of silver to a metallic state (Ag 0 ) and to the formation of silver nanoclusters. The kinetics of clustering during hydrogen diffusion into the glass and diffusion of Ag 0 atoms in the glass matrix have been studied in a temperature ranging from 160 to 200 o C by SEM, AFM and optical spectrometry. The absorption spectra have a peak near 410 nm corresponding to the surface plasmon resonance in Ag clusters. The position of the peak moves as the clusters grow. A theoretical analysis of the absorption spectra allowed us to estimate the cluster size as a function of time, as well as the thickness of the layer filled by clusters, which also changes with time. From AFM data we could measure the kinetics of cluster growth on the surface. We have theoretically analyzed the kinetics of cluster growth during reactive hydrogen diffusion, the kinetics of bulk cluster growth, surface cluster growth, and thickening of the layer filled by clusters. Defect and Diffusion Forum Vols. 237-240 (2005) pp. 689-694 online at http://www.scientific.net

Solid State Phenomena, 2004

Two types of silver-doped glass were used for direct laser recording of 2D and 3D photonic crysta... more Two types of silver-doped glass were used for direct laser recording of 2D and 3D photonic crystals. The first contained a diffusion layer (20 microns thick) with embedded silver nanoclusters of 20-nm average radius. 2D and 3D photonic crystals of submicron lattice parameters were fabricated by nanosecond pulsed laser irradiation (λ, = 355 nm) using four or five coherent intersecting beams. Under irradiation the clusters absorbing light energy are heated to high temperatures and become mobile due to the formation of liquid shells around them. Adjacent clusters move towards each other and towards the irradiated surface under local temperature gradients, form agglomerates and merge in periodically located "spots" of high light intensity in the interference field. The second type of glass, photosensitive to UV irradiation, contained in the bulk Ag + and Ce 3+ ions. Under UV irradiation excited electrons passed from Ce 3+ to Ag + . The Ag atoms became neutral and under subsequent heat treatment of the glass at elevated temperatures have a tendency to form nanoclusters, thus "developing" the UV recorded patterns. Using nanosecond pulsed irradiation of 308 nm we have recorded 3D photonic crystals in the bulk of such glass.

Journal of Physics: Conference Series, 2014

We calculated surface plasmon resonance position for gold and silver hemispheres placed on a diel... more We calculated surface plasmon resonance position for gold and silver hemispheres placed on a dielectric substrate and covered with a thin dielectric layer. The results are applicable in metal islands film enhanced Raman spectroscopy.

Nanoscale research letters, 2015

Unconventional Optical Elements for Information Storage, Processing and Communications, 2000

Materials Science Forum, 1999

physica status solidi (b), 2012

Phone: þ358 13 251 5221, Fax: þ358 13 251 3290

Journal of Applied Physics, 2011

This paper concerns to rigorous analysis of the electrodiffusion problem arising during electric ... more This paper concerns to rigorous analysis of the electrodiffusion problem arising during electric field treatment of glasses and glass metal nanocomposites (e.g. glass poling effect). The strict solution of the carrier drift equations for two type ions differing in mobility and diffusion coefficient is obtained. This solution allows finding out the duration of space charge buildup and determining the limits of electroneutrality approximation. The rigorous solution demonstrates a good agreement with experimental data. The results of numerical solution are discussed as well.

Faraday Discuss., 2015

The paper is dedicated to the recently developed by the authors technique of silver nanoisland gr... more The paper is dedicated to the recently developed by the authors technique of silver nanoisland growth, allowing self-arrangement of 2D-patterns of nanoislands. The technique employs silver out-diffusion from ion-exchanged glass in the course of annealing in hydrogen. To modify the silver ion distribution in the exchanged soda-lime glass we included the thermal poling of the ion-exchanged glass with a profiled electrode as an intermediate stage of the process. The resulting consequence consists of three steps: (i) during the ion exchange of the glass in the AgxNa1-xNO3 (x = 0.01-0.15) melt we enrich the subsurface layer of the glass with silver ions; (ii) under the thermal poling, the electric field displaces these ions deeper into the glass under the 2D profiled anodic electrode, the displacement is smaller under the hollows in the electrode where the intensity of the field is minimal; (iii) annealing in a reducing atmosphere of hydrogen results in silver out-diffusion only in the regions corresponding to the electrode hollows, as a result silver forms nanoislands following the shape of the electrode. Varying the electrode and mode of processing allows governing the nanoisland size distribution and self-arrangement of the isolated single nanoislands, pairs, triples or groups of several nanoislands-so-called plasmonic molecules.

Materials that exhibit third-order nonlinear optical properties have an immense potential for pho... more Materials that exhibit third-order nonlinear optical properties have an immense potential for photonics applications [1]. In this case, it is important to characterize these materials by estimating the third-order nonlinear parameters, viz., two-photon absorption and nonlinear refractive index. In this case, different spectroscopic techniques such as wave mixing, Z-scan and energy scan are generally used to estimate the third-order coefficients [2]. Among the various classes of materials investigated, nonlinear optical glasses have been extensively studied as candidates for ultrafast optical switching (nonresonant nonlinearity) and optical power limiting (resonant nonlinearity). Concerning a resonant process, one of the most investigated high-order nonlinear optical phenomena is based on nonlinear (multi-photon) absorption. Optical power limiters based on nonlinear absorption rely on multi-step processes (reverse saturable absorption) and simultaneous absorption (hereafter called two-photon absorption). The major advantage of optical power limiters based on two-photon absorption is the instantaneous response to the excitation and large dynamic range, provided minimum linear absorption is present.

IEEE Journal of Selected Topics in Quantum Electronics, 2015

ABSTRACT

Technical Physics Letters, 2013

ABSTRACT Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by ... more ABSTRACT Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by selective etching and fixed to a silicon substrate by epoxy glue are studied using luminescence spectroscopy. A disc resonator 6 μm in diameter exhibits quasi-single-mode laser generation at a temperature of 78 K with a threshold power of 320 μW and λ/Δλ ˜ 27000.

Optical Engineering, 2000

A temperature fiber sensor based on CdSe-nanocrystallitedoped phosphate glass as a sensing elemen... more A temperature fiber sensor based on CdSe-nanocrystallitedoped phosphate glass as a sensing element is reported. This glass is shown to exhibit a reversible temperature-induced absorption edge shift at temperatures less than the annealing temperature of the glass (Ͻ370°C). A dual-wavelength detection scheme based on a reflective grating and bi-cell photodiode is employed to eliminate the effects of variable signal losses in the intensity-dependent sensor. A sensor prototype, tested in the temperature range of Ϫ20 to ϩ120°C, is shown to exhibit a linear response to temperature variations.

Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326), 2000

Physical Review B, 2001

Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass... more Coherent acoustic phonon oscillation is observed in PbSe quantum dots embedded in phosphate glass by femtosecond pump-and-probe. The size dependence of the oscillation is investigated. Distinct low-frequency peaks are observed in Raman spectrum for the same samples. The size-dependence of the frequencies is well explained by elastic sphere model, but the observed modes are different to each other for coherent phonon and Raman scattering. Coherent phonon measurement and Raman scattering are found to give complementary information on confined acoustic phonons in this system.

Proceedings of SPIE - The International Society for Optical Engineering

ABSTRACT

Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS

We present results of using PbS-doped phosphate glass with the first excitonic peak at 1.3 μm as ... more We present results of using PbS-doped phosphate glass with the first excitonic peak at 1.3 μm as the saturable absorber for mode-locking of Nd:YAlO3, and Q-switching of Nd:YVO4 and Nd:KGd(WO4)2 lasers.

Glasses embedded with metal nanoclusters are prospective materials which can be used in optical r... more Glasses embedded with metal nanoclusters are prospective materials which can be used in optical recording and laser microfabrication . The conventional way to produce such nanoclusters in a glass consists in doping the glass by metals using ion exchange and subsequent reducing metallic ions to neutral metals . Annealing of metal-doped glasses in a hydrogen atmosphere leads to hydrogen diffusion accompanied by chemical reaction in the doped layer, in which metal ions are reduced to neutral state whereas neutral hydrogen atoms form OH groups and become ions. As solubility of neutral metal atoms in the glass matrix is negligible compared to the ion concentration in the doped layer, reduced metal atoms create high supersaturation in the glass matrix and form nanoclusters.

Technical Digest. Summaries of Papers Presented at the Conference on Lasers and Electro-Optics. Conference Edition. 1998 Technical Digest Series, Vol.6 (IEEE Cat. No.98CH36178), 1998

WEDNESDAY AFTERNOON / CLE0'98 / 251 the variation in y when the incident laser power was 7 W and ... more WEDNESDAY AFTERNOON / CLE0'98 / 251 the variation in y when the incident laser power was 7 W and ambient temperature was varied from 16.5 to 25°C. The oscillatory characteristics can be explained theoretically by considering the thermal expansion of LiNbO, and the difference between dn,/dT and dn,/ dT, where no and ne are the ordinary and extraordinary refractive indices of LiNbO, and T is the temperature, respectively. For this measurement, the angle between the EOM axis and incident polarization was purposely misaligned; for perfect alignment, the amplitude of this oscillatory behavior was reduced by more than two orders of magnitude. The same characteristics were observed in the whole range of laser power.

Defect and Diffusion Forum, 2005

Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag + ions leads to the reduc... more Annealing in a hydrogen atmosphere of silicate glass plates doped by Ag + ions leads to the reduction of silver to a metallic state (Ag 0 ) and to the formation of silver nanoclusters. The kinetics of clustering during hydrogen diffusion into the glass and diffusion of Ag 0 atoms in the glass matrix have been studied in a temperature ranging from 160 to 200 o C by SEM, AFM and optical spectrometry. The absorption spectra have a peak near 410 nm corresponding to the surface plasmon resonance in Ag clusters. The position of the peak moves as the clusters grow. A theoretical analysis of the absorption spectra allowed us to estimate the cluster size as a function of time, as well as the thickness of the layer filled by clusters, which also changes with time. From AFM data we could measure the kinetics of cluster growth on the surface. We have theoretically analyzed the kinetics of cluster growth during reactive hydrogen diffusion, the kinetics of bulk cluster growth, surface cluster growth, and thickening of the layer filled by clusters. Defect and Diffusion Forum Vols. 237-240 (2005) pp. 689-694 online at http://www.scientific.net

Solid State Phenomena, 2004

Two types of silver-doped glass were used for direct laser recording of 2D and 3D photonic crysta... more Two types of silver-doped glass were used for direct laser recording of 2D and 3D photonic crystals. The first contained a diffusion layer (20 microns thick) with embedded silver nanoclusters of 20-nm average radius. 2D and 3D photonic crystals of submicron lattice parameters were fabricated by nanosecond pulsed laser irradiation (λ, = 355 nm) using four or five coherent intersecting beams. Under irradiation the clusters absorbing light energy are heated to high temperatures and become mobile due to the formation of liquid shells around them. Adjacent clusters move towards each other and towards the irradiated surface under local temperature gradients, form agglomerates and merge in periodically located "spots" of high light intensity in the interference field. The second type of glass, photosensitive to UV irradiation, contained in the bulk Ag + and Ce 3+ ions. Under UV irradiation excited electrons passed from Ce 3+ to Ag + . The Ag atoms became neutral and under subsequent heat treatment of the glass at elevated temperatures have a tendency to form nanoclusters, thus "developing" the UV recorded patterns. Using nanosecond pulsed irradiation of 308 nm we have recorded 3D photonic crystals in the bulk of such glass.

Journal of Physics: Conference Series, 2014

We calculated surface plasmon resonance position for gold and silver hemispheres placed on a diel... more We calculated surface plasmon resonance position for gold and silver hemispheres placed on a dielectric substrate and covered with a thin dielectric layer. The results are applicable in metal islands film enhanced Raman spectroscopy.

Nanoscale research letters, 2015

Unconventional Optical Elements for Information Storage, Processing and Communications, 2000

Materials Science Forum, 1999