Showing papers in "Soviet Journal of Quantum Electronics in 1973"
TL;DR: In this article, a theoretical analysis of the escape of α particles generated in the synthesis of deuterium and tritium in a spherical plasma heated to a high temperature by laser radiation is made.
Abstract: A theoretical analysis is made of the escape of α particles generated in the synthesis of deuterium and tritium in a spherical plasma heated to a high temperature by laser radiation. Under these conditions an α particle is slowed down mainly by plasma electrons. Equations are obtained for the fraction of the energy carried away by α particles outside the reaction zone and this energy is found as a function of the dimensions, temperature, and density of the plasma.
45 citations
TL;DR: In this article, a theoretical analysis of the elementary processes occurring in the active medium of an iodine photodissociation laser and affecting its emission spectrum is presented, and the cross sections of the transitions between the hyperfine structure components within the group 2P3/2 and excited 2P1/2 states of atomic iodine are estimated.
Abstract: A theoretical analysis is made of the elementary processes occurring in the active medium of an iodine photodissociation laser and affecting its emission spectrum. An estimate is obtained of the cross sections of the transitions between the hyperfine structure components within the group 2P3/2 and excited 2P1/2 states of atomic iodine, which occur because of collisions with various particles in the active medium. It is shown that typically the mixing of the hyperfine structure components of the state 2P3/2 is very fast in collisions with any particles, whereas the mixing of the sublevels of the state 2P1/2 is primarily due to collisions with iodine atoms in the ground state. Broadening of the stimulated emission line is considered.
33 citations
TL;DR: In this paper, the main mechanism of the population of the laser was the recombination of doubly charged metal ions, which were generated by electron impact and by thermal collisions with helium or neon ions.
Abstract: Stimulated emission pulses were recorded for eight new transitions in mixtures of magnesium, calcium, strontium and barium vapors with helium or neon. The most interesting lines were located in the violet and nearultraviolet region (0.4305 and 0.4162 μ for strontium and 0.3737 μ for calcium) for which a gain of tens of decibels was obtained. It was found that the main mechanism of the population of the laser was the recombination of doubly charged metal ions, which were generated by electron impact and by thermal collisions with helium or neon ions. The deexcitation by electron impact played an important role in the depopulation of the laser levels.
30 citations
TL;DR: In this article, a review of the work carried out abroad and in the Soviet Union on gas-jet laser cutting is given, where the physical basis of the cutting process is considered and the solutions are given of the thermal problems on the assumption that heat sources have point-like and normal intensity distributions.
Abstract: A review is given of the work carried out abroad and in the Soviet Union on gas-jet laser cutting. The physical basis of the cutting process is considered and the solutions are given of the thermal problems on the assumption that heat sources have point-like and normal intensity distributions. Nomograms plotted in terms of dimensionless parameters can be used to calculate numerical values of the cutting rate as a function of the laser power and the thermal properties of the material being cut. The results of the experimental investigations of the cutting of metals and dielectrics are reported. A description is given of a Soviet high-power CO2 laser unit for cutting of sheet materials. Other technological applications (for example, welding) of high-power CO2 lasers are discussed.
28 citations
TL;DR: In this article, a theoretical analysis is given of the attainment of population inversion by optical resonance pumping of the ground-state vibration under conditions ensuring equilibrium of the rotational sublevels, and it is shown that the pumping of a single line makes it possible to achieve laser emission characterized by low energy losses (amounting to a rotational quantum).
Abstract: A theoretical analysis is given of the attainment of population inversion by optical resonance pumping of the ground-state vibration under conditions ensuring equilibrium of the rotational sublevels. It is shown that the pumping of a single line makes it possible to achieve laser emission characterized by low energy losses (amounting to a rotational quantum) in a large number of rotation-vibrational lines, i.e., it is possible to emit simultaneously several laser frequencies. An analysis is made of the dependences of the absorption coefficients of the P, Q, and R lines on the number of the line resonant with the pumping radiation and on the value of the rotational constant. The absorption coefficient (gain) of the 1 → 0 transition of the HF molecule pumped on the P line region is calculated by way of example.
20 citations
TL;DR: In this article, the phase and amplitude modulation characteristics of the light passed through oriented films of nematic liquid crystals with a positive permittivity anisotropy were studied, and the polarization method was used to record changes in the phase delay of light under the action of voltage pulses.
Abstract: A study was made of the phase and amplitude modulation characteristics of the light passed through oriented films of nematic liquid crystals with a positive permittivity anisotropy. The polarization method was used to record changes in the phase delay of light under the action of voltage pulses. The dependence of the optical response on the amplitude and duration of these pulses was determined, switching rates of several kilohertz were achieved by partial reorientation of the molecules in the crystals. Pairs of positive and negative pulses made it possible to eliminate the influence of the pulse repetition frequency on the modulation conditions and to increase the switching rate.
17 citations
TL;DR: In this article, it was shown that undamped spikes in the output of multimode pulsed lasers were due to an inhomogeneous depletion of the inverted population in the bulk of an active rod.
Abstract: The results of an experimental investigation were combined with the published work to show that undamped spikes in the output of multimode pulsed lasers were due to an inhomogeneous depletion of the inverted population in the bulk of an active rod. A quasicontinuous output was obtained from a ruby laser with plane mirrors. It was found that the mechanical and thermal distortions of the resonator, which could suppress the laser action, were essentially misalignments. A new feature of the stimulated emission, called inertia, was observed for a ruby laser with spherical mirrors when the spatial inhomogeneities of the population inversion were smoothed out.
16 citations
TL;DR: In this article, a report of the principal properties of the stimulated emission due to the 4F3/2 → 4I13/2 transitions is given, where the authors identify the stimulated transitions with the crystal splitting schemes of interacting multiplets.
Abstract: A report is given of some of the principal properties of the stimulated emission due to the 4F3/2 → 4I13/2 transitions is Nd3+ ions in SrMoO4, PbMoO4, LiLa(MoO4)2, LiGd(MoO4)2, NaLa(MoO4)2, and NaLa(WO4)2 crystals at 77 and 300°K. For three of these crystals the stimulated transitions are identified with the crystal splitting schemes of interacting multiplets.
16 citations
TL;DR: The energy and power of ultrashort pulses amplified in neodymium glass lasers are restricted by the nonlinear interaction between the laser radiation and the optical medium of the laser itself.
Abstract: The energy and power of ultrashort pulses amplified in neodymium glass lasers are restricted by the nonlinear interaction between the laser radiation and the optical medium of the laser itself. In the case of nearly parallel light beams traveling across an amplifier the restrictions are due to the damage resulting from self-focusing, whereas in the case of diverging beams the restrictions are imposed by the broadening of the spectrum and the scattering of the radiation.
12 citations
TL;DR: In this article, the fifth harmonic of the radiation of a mode-locked neodymium laser was generated in a multistage system using phase-matched four-frequency interaction in calcite (CaCO3) at room temperature.
Abstract: The fifth harmonic of the radiation of a mode-locked neodymium laser was generated in a multistage system. Strong coherent radiation of 200 kW power was obtained at λ5 = 0.212 μ as a result of phase-matched four-frequency interaction in calcite (CaCO3) at room temperature.
11 citations
TL;DR: In this paper, the factors responsible for the multimode emission of injection lasers are considered and a review is given of experimental investigations of this subject, including the use of external and composite resonators.
Abstract: The factors responsible for the multimode emission of injection lasers are considered and a review is given of experimental investigations of this subject. Various methods of spatial and spectral selection of the oscillation modes are described, including particularly the use of external and composite resonators. The applications of single-mode injection lasers are discussed. It is reported that such lasers are used very widely in high-resolution infrared spectroscopy.
TL;DR: In this paper, the two-photon photochromism of spiropyran solutions subjected to ruby laser radiation was investigated and the absorption cross-section of the twophoton absorption cross section was calculated.
Abstract: An investigation was made of the two-photon photochromism of spiropyran solutions subjected to ruby laser radiation. The two-photon absorption cross section of spiropyran was calculated. At high laser radiation intensities the dependence of the optical density of the photoinduced form of spiropyran on the incident radiation intensity deviated from the square law. The cause of this deviation was considered.
TL;DR: In this article, the output power and the current through the laser chamber were determined as a function of N2 and Ne pressures and of the pressures in mixtures of N 2 with Ne and He.
Abstract: An output power of 1.4 MW and an energy of 0.01 J per pulse were achieved for a nitrogen laser emitting at λ = 337.1 nm. The maximum repetition frequency was 20 Hz. The output power and the current through the laser chamber were determined as a function of N2 and Ne pressures and of the pressures in mixtures of N2 with Ne and He. The output power was found to be distributed inhomogeneously over the cross section of the output beam.
TL;DR: In this paper, the absorption spectrum of Cr3+ ions in the ground (4A2) and metastable (2E) states, and of the luminescence spectrum of the same ions in Y3Al5O12 crystals at 300 and 77°K, were investigated.
Abstract: An investigation was made of the absorption spectrum of Cr3+ ions in the ground (4A2) and metastable (2E) states, and of the luminescence spectrum of the same ions in Y3Al5O12 crystals at 300 and 77°K. The effective absorption cross sections were determined for the 4A2 state. The luminescence deexcitation time was found to be 1.5 and 9 msec at 300 and 77°K, respectively. The absorption spectrum of the 2E state had four wide absorption bands with maxima at 16,700, 23,300, 28,600, and 40,500 cm–1. The theoretical energy level scheme of Cr3+ was calculated for Dq = 1725 cm–1, G = 640 cm–1, C = 3200 cm–1, v = 495 cm–1, and v' = 259 cm–1, making an allowance for the mixing of the ΓtrigS states. The experimentally observed absorption bands were attributed to specific transitions and the theoretical and experimental intensities were compared.
TL;DR: In this article, a review of the results of experimental investigations of gas discharge cw and pulsed CO lasers is given, where a large part of the review is concerned with the properties of the laser discharge plasma, which are required for the understanding of the mechanism of population inversion in CO lasers.
Abstract: A review is given of the results of experimental investigations of gas-discharge cw and pulsed CO lasers. A large part of the review is concerned with the properties of the laser discharge plasma, which are required for the understanding of the mechanism of population inversion in CO lasers.
TL;DR: The relaxation time of the transition from the lower laser level 4I11/2 to the ground state 4I9/2 of the Nd3+ ions was determined experimentally for a crystal of Y3Al5O12:Nd3+. The relaxation time was measured by two independent methods as mentioned in this paper.
Abstract: The relaxation time of the transition from the lower laser level 4I11/2 to the ground state 4I9/2 of the Nd3+ ions was determined experimentally for a crystal of Y3Al5O12:Nd3+. The relaxation time was measured by two independent methods. The value obtained, τ21 ≤ 3·10–7 sec, was associated with the very broad (up to ~ 900 cm–1) phonon spectrum of the garnet crystal.
TL;DR: In this paper, the two-photon absorption coefficient of proustite was measured at the ruby and neodymium laser wavelengths at pumping intensities up to 35 MW/cm2.
Abstract: The two-photon absorption coefficient of proustite was measured at the ruby and neodymium laser wavelengths at pumping intensities up to 35 MW/cm2: Its values were 0.1 and 0.03 cm/MW, respectively. The two-photon absorption exhibited no anisotropy associated with the polarization of the incident radiation. An analysis was made of the limiting influence of the two-photon absorption on the efficiency of parametric conversion.
TL;DR: In this article, the results of an investigation of a highly efficient laser frequency doubler utilizing a crystal of cesium dihydrogen arsenate (CDA) were reported.
Abstract: The results are reported of an investigation of a highly efficient laser frequency doubler utilizing a crystal of cesium dihydrogen arsenate (CDA). The high doubling efficiency is due to the considerable width of the phase-matching curve. This width is greater than for other crystals of the KDP group, which includes CDA. Another advantage of this frequency doubler is the ability to operate under 90° phase-matching conditions, which are achieved by heating the crystal to ~45°C.
TL;DR: In this paper, an analysis of the properties of telescopic resonators in which one or both mirrors are replaced by total-internal-reflection prisms is given, and possible applications of such systems are considered.
Abstract: An analysis is given of the properties of telescopic resonators in which one or both mirrors are replaced by total-internal-reflection prisms. Possible applications of such systems are considered.
TL;DR: In this article, an experimental and theoretical investigation was made of the frequency characteristics of a helium-neon laser emitting at λ = 3.39 μ, which contained an absorbing cell filled with methane and produced two orthogonally polarized longitudinal modes.
Abstract: An experimental and theoretical investigation was made of the frequency characteristics of a helium–neon laser emitting at λ = 3.39 μ. The laser contained an absorbing cell filled with methane and it produced two orthogonally polarized longitudinal modes.
TL;DR: In this article, a theoretical analysis is given of the broadening of the spectrum of a giant laser pulse due to the dependence of the refractive index of the active medium on the light intensity.
Abstract: A theoretical analysis is given of the broadening of the spectrum of a giant laser pulse due to the dependence of the refractive index of the active medium on the light intensity. A calculation is given of the integrated effect during the whole of a giant pulse on the assumption that initially the emission is a Gaussian random process. The theoretical estimates are in agreement with specially carried out experiments.
TL;DR: In this article, an experimental investigation was made of the effect of high-power laser radiation on water drops of ~10-2 cm size, and the water drops disintegrated under the action of such radiation.
Abstract: An experimental investigation was made of the effect of high-power laser radiation on water drops of ~10–2 cm size. The drops disintegrated under the action of such radiation. The disintegration was of explosive nature and was attributed to boiling of strongly overheated water at isolated hot spots, which formed as a result of an inhomogeneous distribution of the optical field in a drop.
TL;DR: In this article, a series of solid solutions is formed in which the interchange of gallium and aluminum results only in small changes in the lattice constant, whereas the forbidden-band width varies quite strongly.
Abstract: Considerable success has been achieved in semiconductor lasers by the use of hetero junctions. This use was first suggested back in 1963, soon after the development of the injection laser. However, the advantages of the heterojunction lasers were realized only after the mastering of the epitaxial growth of multilayer structures based on (Al,Ga)As solid solutions. The superiority of the heterojunctions formed in this system is due to the fact that these solid solutions, including pure gallium arsenide, have practically identical crystal lattices irrespective of their composition. This is a consequence of the similarity of the covalent radii of gallium and aluminum. In this way a series of solid solutions is formed in which the interchange of gallium and aluminum results only in small changes in the lattice constant, whereas the forbidden-band width varies quite strongly. Two solid-solution systems – (Al,Ga)As and (Al,Ga)(As,P) – have been used successfully in injection lasers. Heterostructures suitable for injection laser applications can be built from one or several heterojunction and p–n junctions. Double-sided heterojunction structures of the n(Al,Ga)As–pGaAs–p(Al,Ga)As type are characterized by the lowest ever room-temperature values of the threshold current density (less than 1 kA/cm2). This has made it possible to achieve continuous emission from injection lasers at room temperature and up to 355°K. The differential efficiency of uncooled heterojunction lasers has recently been raised to 0.7.
TL;DR: In this paper, the necessary precision in the positioning of elements in unstable resonators is discussed and descriptions of two alignment methods are given, which are now used on routine basis in the laboratories.
Abstract: The necessary precision in the positioning of elements in unstable resonators is discussed. Descriptions are given of two alignment methods which are now used on routine basis in the laboratories.
TL;DR: In this paper, a multistage neodymium-glass laser was constructed and its characteristics were determined, and the output radiation was converted to the second harmonic in a KDP crystal (the energy efficiency of this conversion was in excess of 50%).
Abstract: A multistage neodymium-glass laser was constructed and its characteristics were determined. Introduction of Fabry–Perot interferometers into the mode-locked laser increased the pulse duration to 1 nsec. The output radiation was converted to the second harmonic in a KDP crystal (the energy efficiency of this conversion was in excess of 50%). The output emergy at the second-harmonic wavelength 0.53 μ was 10 J.
TL;DR: In this article, the authors made an analysis of self-diffraction of radiation by gratings formed as a result of bleaching and thermal changes in the refractive index of absorbing and bleachable substances.
Abstract: An analysis is made of self-diffraction of radiation by gratings formed as a result of bleaching and thermal changes in the refractive index of absorbing and bleachable substances. Experimental results are reported for thin layers of solutions of chlorinated gallium and magnesium phthalocyanines in pyridine and of copper sulfate in water. The experimental value of the efficiency of the first-order self-diffraction is close to the theoretical limit for a thin phase grating. A study of spatial images in real time, obtained using a solution of ciyptocyanine in ethanol as a recording material, shows that transient holography can be used for in-line information processing.
TL;DR: In this paper, an experimental investigation was made of the possibility of stabilization of the direction of emission from a solid-state laser when the mirrors of a telescopic resonator were replaced with dihedral prisms having spherical hypotenuse faces.
Abstract: An experimental investigation was made of the possibility of stabilization of the direction of emission from a solid-state laser when the mirrors of a telescopic resonator were replaced with dihedral prisms having spherical hypotenuse faces. The results obtained were in agreement with the theory.
TL;DR: In this article, an experimental investigation was made of the damage of thin metal films by laser radiation and it was found that the evaporation was the main mechanism of the formation of holes in films by short (of the order of 10-8 sec) laser pulses.
Abstract: An experimental investigation was made of the damage of thin metal films by laser radiation. It was found that the evaporation was the main mechanism of the formation of holes in films by short (of the order of 10–8 sec) laser pulses. A detailed comparison of the experimental results with the main consequences of the evaporation model demonstrated a good quantitative agreement between them.
TL;DR: In this article, an investigation was made of self-switching in injection lasers with a single AlxGa1-xAs-As-GaAs heterojunction operating near critical temperature.
Abstract: An investigation was made of self-switching in injection lasers with a single AlxGa1–xAs–GaAs heterojunction operating near critical temperature. A characteristic feature of the self-switching operation was the penetration of the radiation field into the n-type region of the laser diode and the deviation of the angular distribution of the output radiation from the normal to the resonator mirror. The experimental results were in agreement with the expected self-switching in laser diodes with weak waveguide properties.
TL;DR: In this paper, the authors investigated the time constants of spark discharges initiated by a laser beam of λ = 0.3371 μ and 10 kW peak power at pressures of 1-8 atm In a discharge chamber.
Abstract: An investigation was made of the time constants of spark discharges initiated by a laser beam of λ = 0.3371 μ and 10 kW peak power. The experiments were carried out at pressures of 1–8 atm In a discharge chamber. The discharge gap was 1–10 mm and the applied voltage was 10–200 kV. The laser beam was directed onto a copper cathode through a grid-like anode. The discharge delay time varied, depending on the conditions, from 1 to 100 nsec. The fluctuations of the delay time did not exceed ±3 nsec even at voltages close to the static breakdown value. This high stability of the triggering of the discharge gaps indicated that the laser beam in question was a suitable source for initiation of high-power spark discharges.