2005 Quantum Electronics and Laser Science Conference, 2005
ABSTRACT The thermal conductivities of LN and LT were measured. They strongly depended on the non... more ABSTRACT The thermal conductivities of LN and LT were measured. They strongly depended on the nonstoichiometric defect density. Near-stoichiometric LT exhibited the largest thermal conductivity, which is promising a great advantage in QPM frequency conversion.
International Conference on Lasers, Applications, and Technologies 2007: Advanced Lasers and Systems, 2007
ABSTRACT Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is dev... more ABSTRACT Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is developed coupling (i) 8-level rate equations with (ii) TEM00 laser beam distribution, and (iii) complex heat dissipation model. Simulations done for Q-switched ~0.1 J giant pulse generation by Tm,Ho:YLF laser show that ~43 % of the 780 nm light diode side-pumped energy is directly transformed into the heat inside the crystal, whereas ~45 % is the spontaneously emitted radiation from 3F4, 5I7 , 3H4 and 3H5 levels. In water-cooled operation this radiation is absorbed inside the thermal boundary layer where the heat transfer is dominated by heat conduction. In high-power operation the resulting temperature increase is shown to lead to (i) significant decrease in giant pulse energy and (ii) thermal lensing.
2007 Conference on Lasers and Electro-Optics (CLEO), 2007
Numerical simulation suggests two possible ways for optimizing giant pulse of 2.06 mum Q- switche... more Numerical simulation suggests two possible ways for optimizing giant pulse of 2.06 mum Q- switched solid state Tm,Ho: YLF laser by using: (i) a higher Ho doping, 1.0% at., in contrast with 0.4% at., optimal for the normal lasing, and (ii) ap0.7 ms delay in Q-switch opening after 0.5 ms LD pumping.
Lidar Remote Sensing for Environmental Monitoring IX, 2008
ABSTRACT Polycrystalline ceramic with activator ions has already become popular material as laser... more ABSTRACT Polycrystalline ceramic with activator ions has already become popular material as laser medium. In this study, composite type rod which consisted with doped- and undoped-YAG sections was prepared for the laser experiments. By the improvement of pumping chamber, pulse energy of 930 mJ was obtained from oscillator with TEM00 in normal pulse mode at 10 Hz at room temperature. Giant pulse generation was carried out by inserting an AO Q-switch into the laser cavity. Because of the limitation of surface damage thresholds on the laser rod and the mirrors, the maximum output energy up to 21 mJ was obtained.
ABSTRACT A high efficient optical parametric master oscillator power amplifier system for tunable... more ABSTRACT A high efficient optical parametric master oscillator power amplifier system for tunable 820.65 nm generation is presented. This system is suited for an efficient Muonium Lyman-alpha (122.09 nm) generation by a four-wave mixing in Kr.
We report experimental results of second-harmonic (SH) generation (SHG) by a quasi-phase-matched ... more We report experimental results of second-harmonic (SH) generation (SHG) by a quasi-phase-matched periodically poled Mg-doped stoichiometric LiTaO<sub>3</sub> crystal for 1030 nm input radiation of 18 ps pulse duration, within the range of peak input laser intensity I = 0.1-9.5 GW/cm<sup>2</sup> and under repetition rate 10-20 kHz. For I>3 GW/cm<sup>2</sup> SHG efficiency achieves the saturation level of η≈0.35 which can be maintained within a wide range of I = 3-9.5 GW/cm<sup>2</sup>. The loss of SHG efficiency observed for I>5 GW/cm<sup>2</sup> can be recovered to the level of η≈0.35 by using temperature-controlled operation. By applying our experimental data we find the value of two-photon absorption (TPA) coefficient for 515 nm radiation, β≈1.1-2.7 cm/GW, agreeing well with the theoretical estimate β≈2.6 cm/GW. Our analysis suggests that the inhibition of SHG efficiency, its saturation and stabilization are due to ...
Complex thermo-optical model for simulation and optimization of 2 μm co-doped Tm,Ho solid state l... more Complex thermo-optical model for simulation and optimization of 2 μm co-doped Tm,Ho solid state lasers is developed based on (i) 8-levels rate dynamics model for the excitation transfer to Ho3+ ions from LD pumped Tm3+ ions and (ii) the oscillator energy equation with TEM00 distribution for stimulated photons inside the laser cavity. This optical model is rigourosly coupled with two-dimensional time dependent heat transfer model including absorption, heat release and heat transfer inside the operating crystal, as well as thermal effect of spontaneously emitted infrared radiation fluxes. In the case of water cooled laser operation these IR radiations fluxes are shown to be fully absorbed within the water boundary layer of several hundreds microns and to produce a significant inhibition of heat dissipation from the operating crystal. In particular, in case of water cooled operation only ≈40 % of the pumped energy is transformed into the heat directly inside the crystal, whereas ≈45 % ...
Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one mi... more Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one millimeter was observed during explosive ablation of As2S3 glass by femtosecond pulses at high fluence (> 5 J/cm2) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. However, the spheres of up to several microns in diameter are found to form competing with nano-fiber formation and significantly deteriorating their morphology. The formation of these spheres is explained by the free energy minimization of explosively ablating liquid jets combined with the onset and evolution of the thermo-capillary forces at the local perturbations of the geometry and temperature. Performed thermal analysis suggests that the good nano-fiber morphology can be preserved by increasing the air pressure or ablation in water which shortens the characteristic cooling and solidification time of the liquid jets, and inhibits the development of the small geometrical perturbations into the large sp...
Physical review. E, Statistical, nonlinear, and soft matter physics, 2002
In this paper, the growth stability of open-ended carbon nanotubes mediated by surface diffusion ... more In this paper, the growth stability of open-ended carbon nanotubes mediated by surface diffusion on the lateral surface of the nanotube is considered in detail. Nanotube growth and destabilization is viewed as a competition of two processes at the open growth edge: (i) hexagon formation sustaining the continuous growth of the regular hexagonal network, and (ii) thermally activated pentagon formation, which causes inward bending of the nanotube wall resulting in end closure, i.e., growth termination. The edge of the open-ended nanotube, if it is fed by a sufficiently large surface diffusion flux, may remain stable even without extrinsic stabilizing effects. The closure of the open end of the growing nanotube is shown to happen whenever a change in the growth conditions (temperature, carbon vapor pressure, or surface area from which the open end is fed) decreases the surface diffusion flux, and the characteristic time for new atom arrival on the edge becomes larger than the characteri...
2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006
ABSTRACT Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 cry... more ABSTRACT Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 crystals reveals the complex spatio-temporal evolution of the 1.064 mum fundamental harmonic and second harmonic energy fields with associated temperature fields, leading to the thermal dephasing and inhibition of second harmonic generation.
Photonics: Design, Technology, and Packaging II, 2005
Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 and LiTaO3 c... more Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 and LiTaO3 crystals reveals the complex spacio-temporal evolution of the 1.064 mum fundamental harmonic (FH) and second harmonic (SH) energy fields with associated temperature fields, leading to the thermal dephasing and inhibition of second harmonic generation (SHG). The investigated range of the laser input power is W0=0.5-50 W (with
International Conference on Lasers, Applications, and Technologies 2007: Laser-assisted Micro- and Nanotechnologies, 2007
ABSTRACT Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length ... more ABSTRACT Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one millimeter was observed during explosive ablation of As2S3 glass by femtosecond pulses at high fluence (&gt; 5 J/cm2) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. However, the spheres of up to several microns in diameter are found to form competing with nano-fiber formation and significantly deteriorating their morphology. The formation of these spheres is explained by the free energy minimization of explosively ablating liquid jets combined with the onset and evolution of the thermo-capillary forces at the local perturbations of the geometry and temperature. Performed thermal analysis suggests that the good nano-fiber morphology can be preserved by increasing the air pressure or ablation in water which shortens the characteristic cooling and solidification time of the liquid jets, and inhibits the development of the small geometrical perturbations into the large spheres.
2005 Quantum Electronics and Laser Science Conference, 2005
ABSTRACT The thermal conductivities of LN and LT were measured. They strongly depended on the non... more ABSTRACT The thermal conductivities of LN and LT were measured. They strongly depended on the nonstoichiometric defect density. Near-stoichiometric LT exhibited the largest thermal conductivity, which is promising a great advantage in QPM frequency conversion.
International Conference on Lasers, Applications, and Technologies 2007: Advanced Lasers and Systems, 2007
ABSTRACT Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is dev... more ABSTRACT Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is developed coupling (i) 8-level rate equations with (ii) TEM00 laser beam distribution, and (iii) complex heat dissipation model. Simulations done for Q-switched ~0.1 J giant pulse generation by Tm,Ho:YLF laser show that ~43 % of the 780 nm light diode side-pumped energy is directly transformed into the heat inside the crystal, whereas ~45 % is the spontaneously emitted radiation from 3F4, 5I7 , 3H4 and 3H5 levels. In water-cooled operation this radiation is absorbed inside the thermal boundary layer where the heat transfer is dominated by heat conduction. In high-power operation the resulting temperature increase is shown to lead to (i) significant decrease in giant pulse energy and (ii) thermal lensing.
2007 Conference on Lasers and Electro-Optics (CLEO), 2007
Numerical simulation suggests two possible ways for optimizing giant pulse of 2.06 mum Q- switche... more Numerical simulation suggests two possible ways for optimizing giant pulse of 2.06 mum Q- switched solid state Tm,Ho: YLF laser by using: (i) a higher Ho doping, 1.0% at., in contrast with 0.4% at., optimal for the normal lasing, and (ii) ap0.7 ms delay in Q-switch opening after 0.5 ms LD pumping.
Lidar Remote Sensing for Environmental Monitoring IX, 2008
ABSTRACT Polycrystalline ceramic with activator ions has already become popular material as laser... more ABSTRACT Polycrystalline ceramic with activator ions has already become popular material as laser medium. In this study, composite type rod which consisted with doped- and undoped-YAG sections was prepared for the laser experiments. By the improvement of pumping chamber, pulse energy of 930 mJ was obtained from oscillator with TEM00 in normal pulse mode at 10 Hz at room temperature. Giant pulse generation was carried out by inserting an AO Q-switch into the laser cavity. Because of the limitation of surface damage thresholds on the laser rod and the mirrors, the maximum output energy up to 21 mJ was obtained.
ABSTRACT A high efficient optical parametric master oscillator power amplifier system for tunable... more ABSTRACT A high efficient optical parametric master oscillator power amplifier system for tunable 820.65 nm generation is presented. This system is suited for an efficient Muonium Lyman-alpha (122.09 nm) generation by a four-wave mixing in Kr.
We report experimental results of second-harmonic (SH) generation (SHG) by a quasi-phase-matched ... more We report experimental results of second-harmonic (SH) generation (SHG) by a quasi-phase-matched periodically poled Mg-doped stoichiometric LiTaO<sub>3</sub> crystal for 1030 nm input radiation of 18 ps pulse duration, within the range of peak input laser intensity I = 0.1-9.5 GW/cm<sup>2</sup> and under repetition rate 10-20 kHz. For I>3 GW/cm<sup>2</sup> SHG efficiency achieves the saturation level of η≈0.35 which can be maintained within a wide range of I = 3-9.5 GW/cm<sup>2</sup>. The loss of SHG efficiency observed for I>5 GW/cm<sup>2</sup> can be recovered to the level of η≈0.35 by using temperature-controlled operation. By applying our experimental data we find the value of two-photon absorption (TPA) coefficient for 515 nm radiation, β≈1.1-2.7 cm/GW, agreeing well with the theoretical estimate β≈2.6 cm/GW. Our analysis suggests that the inhibition of SHG efficiency, its saturation and stabilization are due to ...
Complex thermo-optical model for simulation and optimization of 2 μm co-doped Tm,Ho solid state l... more Complex thermo-optical model for simulation and optimization of 2 μm co-doped Tm,Ho solid state lasers is developed based on (i) 8-levels rate dynamics model for the excitation transfer to Ho3+ ions from LD pumped Tm3+ ions and (ii) the oscillator energy equation with TEM00 distribution for stimulated photons inside the laser cavity. This optical model is rigourosly coupled with two-dimensional time dependent heat transfer model including absorption, heat release and heat transfer inside the operating crystal, as well as thermal effect of spontaneously emitted infrared radiation fluxes. In the case of water cooled laser operation these IR radiations fluxes are shown to be fully absorbed within the water boundary layer of several hundreds microns and to produce a significant inhibition of heat dissipation from the operating crystal. In particular, in case of water cooled operation only ≈40 % of the pumped energy is transformed into the heat directly inside the crystal, whereas ≈45 % ...
Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one mi... more Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one millimeter was observed during explosive ablation of As2S3 glass by femtosecond pulses at high fluence (> 5 J/cm2) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. However, the spheres of up to several microns in diameter are found to form competing with nano-fiber formation and significantly deteriorating their morphology. The formation of these spheres is explained by the free energy minimization of explosively ablating liquid jets combined with the onset and evolution of the thermo-capillary forces at the local perturbations of the geometry and temperature. Performed thermal analysis suggests that the good nano-fiber morphology can be preserved by increasing the air pressure or ablation in water which shortens the characteristic cooling and solidification time of the liquid jets, and inhibits the development of the small geometrical perturbations into the large sp...
Physical review. E, Statistical, nonlinear, and soft matter physics, 2002
In this paper, the growth stability of open-ended carbon nanotubes mediated by surface diffusion ... more In this paper, the growth stability of open-ended carbon nanotubes mediated by surface diffusion on the lateral surface of the nanotube is considered in detail. Nanotube growth and destabilization is viewed as a competition of two processes at the open growth edge: (i) hexagon formation sustaining the continuous growth of the regular hexagonal network, and (ii) thermally activated pentagon formation, which causes inward bending of the nanotube wall resulting in end closure, i.e., growth termination. The edge of the open-ended nanotube, if it is fed by a sufficiently large surface diffusion flux, may remain stable even without extrinsic stabilizing effects. The closure of the open end of the growing nanotube is shown to happen whenever a change in the growth conditions (temperature, carbon vapor pressure, or surface area from which the open end is fed) decreases the surface diffusion flux, and the characteristic time for new atom arrival on the edge becomes larger than the characteri...
2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006
ABSTRACT Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 cry... more ABSTRACT Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 crystals reveals the complex spatio-temporal evolution of the 1.064 mum fundamental harmonic and second harmonic energy fields with associated temperature fields, leading to the thermal dephasing and inhibition of second harmonic generation.
Photonics: Design, Technology, and Packaging II, 2005
Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 and LiTaO3 c... more Computational study of nanosecond pulse laser radiation in periodically poled LiNbO3 and LiTaO3 crystals reveals the complex spacio-temporal evolution of the 1.064 mum fundamental harmonic (FH) and second harmonic (SH) energy fields with associated temperature fields, leading to the thermal dephasing and inhibition of second harmonic generation (SHG). The investigated range of the laser input power is W0=0.5-50 W (with
International Conference on Lasers, Applications, and Technologies 2007: Laser-assisted Micro- and Nanotechnologies, 2007
ABSTRACT Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length ... more ABSTRACT Formation of nano-fibers ranging from 30 to 300 nm in diameter and exceeding the length of one millimeter was observed during explosive ablation of As2S3 glass by femtosecond pulses at high fluence (&gt; 5 J/cm2) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. However, the spheres of up to several microns in diameter are found to form competing with nano-fiber formation and significantly deteriorating their morphology. The formation of these spheres is explained by the free energy minimization of explosively ablating liquid jets combined with the onset and evolution of the thermo-capillary forces at the local perturbations of the geometry and temperature. Performed thermal analysis suggests that the good nano-fiber morphology can be preserved by increasing the air pressure or ablation in water which shortens the characteristic cooling and solidification time of the liquid jets, and inhibits the development of the small geometrical perturbations into the large spheres.
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