Showing papers in "Quantum Electronics in 2005"
TL;DR: In this paper, a new fiber laser based on a bismuth-doped aluminosilicate glass fiber is proposed and fabricated and obtained in the spectral region between 1150 and 1300 nm.
Abstract: A new fibre laser based on a bismuth-doped aluminosilicate glass fibre is proposed and fabricated. CW lasing is obtained in the spectral region between 1150 and 1300 nm. The fibres are fabricated by the method of modified chemical vapour deposition.
315 citations
TL;DR: In this paper, a brief review of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings is given. But the most important properties of fiber gratings are considered and the main methods of their production and their applications are discussed.
Abstract: A brief review is given of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings. The most important properties of fibre gratings are considered and the main methods of their production and their applications are discussed. The photosensitive compositions of silica glasses are presented and methods for increasing their photosensitivity are indicated.
149 citations
TL;DR: In this article, the authors studied the dynamics of dark solitons in a parabolic trap with an external harmonic potential and provided a comparative analysis of the solutions of nonstationary problems for a linear harmonic oscillator and the NSE model with a harmonic potential.
Abstract: The dynamics of dark solitons is studied within the framework of the mathematical model of nonlinear Schrodinger equation (NSE) with an external harmonic potential. A comparative analysis of the solutions of nonstationary problems is performed for a linear harmonic oscillator and the NSE model with a harmonic potential for different signs of the self-action potential. It is shown that the main specific feature of the dynamics of dark NSE solitons in a parabolic trap is the formation of solitons with dynamically changing form factors producing the periodic variation in the modulation depth (the degree of 'blackness') of dark solitons. The oscillation period of the dark soliton does not coincide with the oscillation period of a linear quantum-mechanical oscillator, which is caused by the periodic transformation of the black soliton to the grey one and vice versa. The conditions of applicability of the method of inverse scattering problem are presented, the generalised Lax pair is found, and exact soliton solutions are given for the mathematical NSE model with an external harmonic potential.
68 citations
TL;DR: In this paper, the authors studied the effect of the laser-pulse duration on the thickness of polycrystalline diamond surface and showed that the diamond graphitisation during multipulse laser ablation is a thermally stimulated process, and the dependence of the diamond-ablation rates on the radiation energy density under the action of laser pulses of various durations.
Abstract: Processes of graphitisation of laser-irradiated polycrystalline diamond surface exposed to multipulse irradiation are studied experimentally. The thickness of the laser-modified layer as a function of the laser-pulse duration ranging from 100 fs to 1.5 μs and the effect of the radiation wavelength on this thickness are studied. It is shown that the diamond graphitisation during multipulse laser ablation is a thermally stimulated process. The dependences of the diamond-ablation rates on the radiation energy density under the action of laser pulses of various durations are presented.
65 citations
TL;DR: In this paper, the formation of plasma channels of a femtosecond laser pulse in the bulk of fused silica is studied by numerical simulation, and the advantages of using a conical lens (axicon) over conventional parabolic lenses are shown.
Abstract: The formation of plasma channels of a femtosecond laser pulse in the bulk of fused silica is studied by numerical simulation, and the advantages of using a conical lens (axicon) over conventional parabolic lenses are shown. It is found that the length of the plasma channel formed with the help of an axicon exceeds the length of the channel formed upon lens focusing.
65 citations
TL;DR: In this article, a general approach is described to the rates, fluxes and current densities associated with spontaneous radiative and nonradiative Auger recombinations in heterostructure lasers with different types of a quantum-confined active region (quantum wells, quantum wires, and quantum dots).
Abstract: General approach is described to the rates, fluxes and current densities associated with spontaneous radiative and nonradiative Auger recombinations in heterostructure lasers with different types of a quantum-confined active region (quantum wells, quantum wires, and quantum dots). The proper way of defining the spontaneous radiative and Auger recombination coefficients and their dimensionality are discussed. It is shown that only in a quantum dot, true time constants can be introduced for spontaneous radiative and nonradiative Auger recombinations, which are independent of the injection level. Closed-form elegant expressions are presented for the radiative recombination coefficient as an explicit function of temperature and parameters in bulk and quantum-confined structures. These expressions clearly demonstrate inappropriateness of the common practice of deriving the recombination coefficients in low-dimensional heterostructures from the bulk values.
35 citations
TL;DR: In this article, the temperature dependence of the efficiency of a laser based on a Fe:ZnSe crystal grown from the vapour phase by the free-growth method was studied in the 85-255-K temperature range.
Abstract: The temperature dependence of the efficiency of a laser based on a Fe:ZnSe crystal grown from the vapour phase by the free-growth method is studied in the 85–255-K temperature range. As the temperature was increased, the slope efficiency of the laser with respect to absorbed energy decreased from 43% (at 85 K) down to 9% (at 255 K) and its emission spectrum shifted from 4.0 to 4.17 μm. Lasing was obtained in a Fe2+:ZnSe crystal cooled with a thermoelectric module down to ~220 K. In this case, the slope efficiency of the laser with respect to absorbed energy was 30%. The output energy of the thermoelectrically cooled laser was 142 mJ for the slope efficiency with respect to the incident pump energy equal to 21%.
35 citations
TL;DR: In this article, the amplification of weak 80−240mJ, 4-ns laser pulses with a gain of 0.035−0.045 cm-1 was studied.
Abstract: The amplification of weak 80–240-mJ, 4-ns laser pulses with a gain of 0.035–0.045 cm-1 is studied. The maximum energy of 3.3 kJ is obtained for 4-ns pulses.
33 citations
TL;DR: In this article, the results of the development of repetitively pulsed, diode-pumped, electro-optically controlled picosecond Nd:YAG lasers of two designs are presented.
Abstract: The results of the development of repetitively pulsed, diode-pumped, electro-optically controlled picosecond Nd:YAG lasers of two designs are presented. The first design uses the active—passive mode locking with electro-optical lasing control and semiconductor saturable absorber mirrors (SESAM). This design allows the generation of 15–50-ps pulses with an energy up to 0.5 mJ and a maximum pulse repetition rate of 100 Hz. The laser of the second design generates 30-ps pulses due to combination of positive and negative electro-optical feedback and the control of the electro-optical modulator by the photocurrent of high-speed semiconductor structures.
32 citations
TL;DR: In this paper, singlemode cw Yb-, Er?Yb, and Nd-doped fiber lasers are fabricated by using fibres of a complicated structure (a few silica fibres in optical contact with each other are surrounded by a polymer jacket), which allows the coupling of radiation from several pump sources into one active fibre, providing an increase in the output power of the fibre laser.
Abstract: Single-mode cw Yb-, Er?Yb, and Nd-doped fibre lasers are fabricated by using fibres of a complicated structure (a few silica fibres in optical contact with each other are surrounded by a polymer jacket). Such a structure allows the coupling of radiation from several pump sources into one active fibre, providing an increase in the output power of the fibre laser. The Yb-doped fibre lasers with the output power above 50 W and efficiency ~65% and the 1.608-?m Er?Yb-doped fibre laser pumped to the absorption band of Yb are fabricated and studied. The Nd-doped fibre lasers based on such fibres and emitting at 0.92 and 1.06 ?m are manufactured for the first time.
31 citations
TL;DR: In this paper, a five-stage neodymium phosphate glass amplifier producing 1.5 ns radiation pulses of energy up to 110 J was described, where the use of a multistage spatial filter based on an aperture line provided efficient extraction of the stored energy.
Abstract: A five-stage neodymium phosphate glass amplifier producing 1–1.5-ns radiation pulses of energy up to 110 J is described. The use of a multistage spatial filter based on an aperture line provides efficient extraction of the stored energy. The exit aperture filling factor is 0.65 and the output radiation divergence is equal to three times the diffraction-limited divergence. The energy efficiency of radiation conversion to the second harmonic is 60%. The amplifier is intended for pumping a chirped-pulse optical parametric amplifier.
TL;DR: In this paper, the optical properties of a composite medium comprised of metallic nanospheres located at the sites of a three-dimensional lattice and embedded into a dielectric matrix are considered.
Abstract: Optical properties of a composite medium comprised of metallic nanospheres located at the sites of a three-dimensional lattice and embedded into a dielectric matrix are considered. It is shown that for a certain ratio of the dielectric constants, the refractive index of the composite medium may be equal to unity. A method taking into account the delay effects during interaction of nanospheres with radiation has been developed to describe the optical properties of the composite medium. It is shown that in the limit when the distances between nanospheres are negligibly small compared to the wavelength, the results coincide with the results of the Maxwell-Garnett theory. (nanotechnologies)
TL;DR: In this article, a new mechanism of the continuous frequency down-conversion of a pulse propagating in a uniaxial crystal under conditions of the Zakharov?Benney resonance between its ordinary and extraordinary components is proposed.
Abstract: A new mechanism of the continuous frequency down-conversion of a pulse propagating in a uniaxial crystal under conditions of the Zakharov?Benney resonance between its ordinary and extraordinary components is proposed. Unlike stimulated Raman self-scattering, here the red frequency shift of the ordinary component saturates, achieving its maximum value at some propagation length, which is proportional to the input pulse intensity. The ordinary component generates an ultimately short single pulse of the extraordinary wave propagating in the soliton regime. It is shown that this effect can be observed only in a crystal with the positive birefringence.
TL;DR: In this paper, a terahertz (THz) pulses were generated by optical rectification of femtosecond laser pulses in a ZnTe crystal, and a substantial decrease in the THz radiation power was observed upon tight focusing of laser radiation into the crystal.
Abstract: The generation of terahertz (THz) pulses by the optical rectification of femtosecond laser pulses in a ZnTe crystal is studied. A substantial decrease in the THz radiation power was observed upon tight focusing of laser radiation into the crystal. It is shown that the consideration of competing two-photon absorption and second-harmonic generation processes proceeding simultaneously with optical rectification cannot explain this effect even qualitatively. It is assumed that the observed decrease in the THz radiation power is caused by a decrease in the size of a source of nonlinear polarisation. The conditions are found for the most efficient generation of THz radiation in the ZnTe crystal.
TL;DR: The theory of Coulomb explosion of a plasma was used to estimate the maximum energy of ions produced upon irradiation of an ultrathin foil by a relativistically strong ultrashort laser pulse as mentioned in this paper.
Abstract: The theory of Coulomb explosion of a plasma is used to estimate the maximum energy of ions produced upon irradiation of an ultrathin foil by a relativistically strong ultrashort laser pulse.
TL;DR: In this article, the effect of a constant dipole moment of the resonance transition on the formation of self-induced transparency pulses and their spectral composition is studied, and the propagation of few-cycle electromagnetic pulses through an anisotropic medium is considered.
Abstract: The propagation of few-cycle electromagnetic pulses through an anisotropic medium is considered. The effect of a constant dipole moment of the resonance transition on the formation of self-induced transparency pulses and their spectral composition is studied.
TL;DR: In this paper, an optical fiber with a heavily GeO2-doped core and fused silica cladding was used for the first time to produce a Raman laser with 10 W at a fibre length of only 3 m and Raman lasers emitting at 1.73, 1.85, 2.06, and 2.2 μm.
Abstract: Amplification of radiation due to stimulated Raman scattering in an optical fibre with a heavily GeO2-doped core and a fused silica cladding is studied. The applications of such fibres in Raman lasers are demonstrated. A Raman fibre laser emitting 10 W at a fibre length of only 3 m and Raman lasers emitting at 1.73, 1.85, 2.06, and 2.2 μm are fabricated for the first time.
TL;DR: An all-fibre single-mode cw ytterbium laser based on a three-element first cladding fibre with an output power of 100W is fabricated in this article.
Abstract: Pump radiation transfer is studied experimentally in multi-element first cladding laser fibres. A model of this process is proposed, which is in good agreement with experimental results. An all-fibre single-mode cw ytterbium laser based on a three-element first cladding fibre with an output power of 100W is fabricated.
TL;DR: In this paper, the results of recent studies on coherent acousto-optic image processing performed at the chair of physics of oscillations at the Department of Physics of Moscow State University are reported.
Abstract: The results of recent studies on coherent acousto-optic image processing performed at the chair of physics of oscillations at the Department of Physics of Moscow State University are reported. It is shown that this processing method is based on the filtration of the spatial spectrum of an optical signal in an acousto-optic cell. The main attention is paid to the analysis of the dependence of the transfer function of the cell on the crystal cut, geometry of acousto-optic interaction, and acoustic-wave parameters. It is shown that an acousto-optic cell allows the image differentiation and integration as well as the visualisation of phase objects. The results of experiments and computer simulation are presented which illustrate the possibilities of acousto-optic image processing.
TL;DR: In this paper, the relative concentration of erbium ions undergoing nonradiative relaxation from the metastable to the ground level is measured in aluminosilicate glass fibres doped with Erbium ion at concentration between 3×1018 and 1020 cm-3.
Abstract: The relative concentration of erbium ions undergoing nonradiative relaxation from the metastable to the ground level is measured in aluminosilicate glass fibres doped with erbium ions at concentration between 3×1018 and 1020 cm-3. The dependence of the fraction of such ions on the Er3+ concentration is determined for fibres containing different amounts of aluminium oxide in a core. It is shown that the fraction of erbium ions not involved in amplification substantially decreases with increasing the Al2O3 concentration. It is found that clustering leads to a considerable decrease in the gain in heavily Er3+-doped active fibres. The dependence of the quantum efficiency of a fibre amplifier on the erbium ion concentration is obtained based on the measurements performed. This dependence can be used for optimising the parameters of erbium-doped fibre amplifiers.
TL;DR: In this article, the first stage of development of the experimental technique for obtaining weight amounts of the highly enriched 150Nd isotope by laser photoionisation is presented and the vaporiser and the laser are designed, and various methods of irradiation of neodymium vapour and extraction of photoions are tested.
Abstract: Results obtained at the first stage of development of the experimental technique for obtaining weight amounts of the highly enriched 150Nd isotope by laser photoionisation are presented. The vaporiser and the laser are designed, and various methods of irradiation of neodymium vapour and extraction of photoions are tested. The product yield ~40 mg h-1 for the ~60% enrichment and 25 mg h-1 for the ~65% enrichment is achieved for a vaporiser of length 27 cm. The cost of constructing the facility for preparing 50 kg of the 150Nd isotope, intended for determining the neutrino mass, is estimated. This estimate shows that the cost of production can be lowered by a factor of 5?7 compared to the electromagnetic method.
TL;DR: In this paper, the role of coherent optical radiation in photoregulatory processes caused by chemiluminescence of living cells is discussed and the effect of low and highly coherent quasi-monochromatic light on a dynamic 'host-parasite' system is studied.
Abstract: The role of coherent optical radiation in photoregulatory processes caused by chemiluminescence of living cells is discussed. The effect of low and highly coherent quasi-monochromatic light on a dynamic 'host—parasite' system is studied. It is shown that plant organisms can distinguish the statistical order of irradiation. A significant increase in the functional activity was observed only for cells that were completely located within the coherence volume of the electromagnetic field. It is concluded that the cell size in living organisms is the discrimination threshold of the statistical properties of radiation and may serve as a specific biological measure of coherence.
TL;DR: In this article, the growth dynamics of intracavity absorption during recording line absorption spectra was studied using a pulsed Cr2+:ZnSe laser tunable between 2.1 and 3.1 μm.
Abstract: The growth dynamics of intracavity absorption is studied during recording line absorption spectra by the method of intracavity laser spectroscopy using a pulsed Cr2+:ZnSe laser tunable between 2.1 and 3.1 μm. In the lasing duration range from 0 to 235 μs, an intracavity absorption signal increases linearly with time, providing the effective absorption length of 70km.
TL;DR: In this paper, the M2 factor was calculated for the super-Gaussian intensity distribution with phase distortions caused by the electron and thermal self-focusing and spherical aberration.
Abstract: The method is proposed for calculating the M2 factor by using the averaged description of wave beams (the method of moments). The values of M2 are calculated for the super-Gaussian intensity distribution with phase distortions caused by the electron and thermal self-focusing and spherical aberration.
TL;DR: In this paper, small-angle scattering of laser radiation in purified (two-distilled) water is studied experimentally and the results obtained in the paper confirm the earlier proposed hypothesis about the presence of stable microbubbles of gas, bubstons, dissolved in pure liquids.
Abstract: Small-angle scattering of laser radiation in purified (twice-distilled) water is studied experimentally. The scattering indicatrix shows that such water contains scattering micron impurities. The parameters of the size distribution of these impurities are estimated from the experimental data. The results obtained in the paper confirm the earlier proposed hypothesis about the presence of stable microbubbles of gas, bubstons, dissolved in pure liquids.
TL;DR: In this paper, an optical parametric oscillator (OPO) was obtained for the first time in an Hg1-xCdxGa2S4 crystal pumped by a nanosecond Nd:YAG laser.
Abstract: Lasing was obtained for the first time in an optical parametric oscillator (OPO) on an Hg1-xCdxGa2S4 crystal pumped by a nanosecond Nd:YAG laser. Due to the cadmium concentration gradient along the crystal axis, the OPO could be tuned under noncritical phase-matching conditions by a linear displacement of the crystal. The tuning range was 2.85–3.27 μm, with the maximum slope conversion efficiency equal to 6.6%.
TL;DR: In this article, the formation of many filaments in a laser pulse with initial perturbations of the intensity propagated in a turbulent atmosphere is studied numerically, and it is shown that the competition between nonlinear focuses can slow down the creation of filaments during their propagation.
Abstract: The formation of many filaments in a laser pulse with initial perturbations of the intensity propagated in a turbulent atmosphere is studied numerically. It is shown that the competition between nonlinear focuses can slow down the formation of filaments during their propagation. The number of filaments in the turbulent atmosphere increases with distance. Nonstationary interference upon defocusing in a laser plasma leads to the appearance of secondary filaments. The dynamic competition between filaments produced during the pulse shortens their length and the length of plasma channels.
TL;DR: In this paper, the effect of laser radiation characteristics on the surface shape and cut depth in cutting stainless steel sheets is investigated numerically, and it is shown for the first time that the cutting of materials by the TEM00 beam is most efficient when the beam has elliptical polarisation directed along the direction of beam displacement and characterised by a specific axial ratio.
Abstract: The effect of polarisation of a Gaussian beam on the radiation absorption during laser cutting of metals is investigated. A generalised formula is proposed for calculating the absorption coefficient, which describes the polarisation of three types (linear, elliptical, and circular), taking into account the fact that the beam may interact with a metal surface of an arbitrary shape. A comparison with the existing analogues (in the cases of linear and circular radiation polarisation) confirmed the advantage of employing the formula for the spatial description of the shape of the surface produced, which is highly important for processing (cutting, welding, drilling) of thick materials. The effect of laser radiation characteristics on the surface shape and cut depth in cutting stainless steel sheets is investigated numerically. It is shown for the first time that the cutting of materials by the TEM00 beam is most efficient when the beam has elliptical polarisation directed along the direction of beam displacement and characterised by a specific axial ratio.
TL;DR: In this article, a femtosecond Er3+-doped fiber laser system was developed and studied, which contains a master oscillator operating in the pulse stretching regime, an amplifier of chirped pulses and a device for pulse compression.
Abstract: A femtosecond Er3+-doped fibre laser system is developed and studied. The system contains a master oscillator operating in the pulse stretching regime, an amplifier of chirped pulses, and a device for pulse compression. The laser emits 1.55-μm, 100-fs, 90-mW pulses with a pulse repetition rate of 25 MHz. The setup was used for supercontinuum generation in an optical fibre heavily doped with GeO2. The width of the generated supercontinuum was close to an octave.
TL;DR: In this paper, the second and third harmonics of a femtosecond Cr:forsterite laser radiation were generated using a single-input single-output (SISO) system.
Abstract: Highly efficient generation of the second (?2?=69%) and third (?3?=26%) harmonics of a femtosecond Cr:forsterite laser radiation is achieved. It is shown that for the pump intensity exceeding 50 GW cm-2 (?2?=60%), the third-order nonlinearity begins to play a significant role, resulting in a deterioration of the spectral parameters of the generated harmonics.