Table of contents

A description is given of a neodymium-glass laser spectrometer with a dispersive resonator. This spectrometer operates in the 9230–9520 cm^–1 range with a resolution between 0.1 and 0.02 cm^–1 and can be used to detect absorption characterized by a coefficient of 10^–7 cm^–1. This spectrometer was used to obtain a low-resolution record of the P branch of the 12⁰3 band, the 04⁰3 band, and the "hot" 13¹3→01¹0 transition in carbon dioxide gas as well as the absorption spectra of atmospheric air and water vapor. A high-resolution record was obtained of the edge of the 04⁰3 band and the distances between the lines were measured.

It is shown that efficient conversion of wide-band pump radiation in a Raman laser cannot be combined with a reduction of the angular divergence below that of the pump radiation.

An investigation was made of the time and energy characteristics of a self-terminating (cyclic) gas laser utilizing europium atoms and ions and operating in a periodic self-heating regime. The active medium was excited by a system based on the Blumlein circuit. The total average radiation power due to atomic transitions was 1.95 W at the optimal (ν=10 kHz) pulse repetition frequency in a tube 2 cm in diameter and 46 cm long. The total average radiation power of the ionic lines was ~10 mW (for the same repetition frequency).

An experimental investigation was made of the dependence of the power of stimulated Brillouin scattering (SBS) on the pump power and also of the dependence of the shift of the SBS components in several aqueous solutions of acids and salts on their concentration. The SBS gain was greatly affected even by low concentrations (of the order of a few percent by weight) and the change in gain altered the SBS signal amplitude by several orders of magnitude. The investigated salts reduced the gain, acids (with the exception of H₂SO₄) increased the gain, and sulfuric acid first increased and then strongly reduced the gain. The observed dependences could be explained by a change in the absorption of hypersound resulting from the frequency shift of relaxation processes of the dissociation-association type.

Explosion of absorbing water drops, 50–800μ diameter, interacting with ruby laser pulses was investigated experimentally. Inhomogeneity of the internal optical field in drops characterized by an extinction coefficient of ~10^–4 resulted in local ejection of fine fragments in the direction of propagation of the laser beam and altered the shape of water drops. The final fragmentation of the drops was a threshold process and it was due to heating of the drops to a temperature close to the critical value.

An experimental study was made of the bleaching of an aqueous aerosol (artificial fog) by CO₂ laser radiation pulses of ~50 W/cm² power density. An analytic dependence of the degree of bleaching on the initial optical thickness of the aerosol was obtained. This dependence and the experimental results were used to find the efficiency of aerosol evaporation.

A theoretical explanation is given of why an increase in the number of modes in laser radiation alters (reduces) the diffraction efficiency of focused holograms obtained by diffuse scattering of the reference beam. It is shown that the visibility of interference fringes obtained in recording of these holograms is governed by the degree of the temporal coherence of the radiation so that it is possible to derive the theoretical dependence of the diffraction efficiency on the number of longitudinal modes and this dependence is in good agreement with the experimental results.

Four-frequency and two-stage three-frequency interactions are considered as the basis of two autocorrelation methods. The second method is more effective in the case of noncentrosymmetric media. Autocorrelations of objects obtained experimentally are reproduced and it is shown that autocorrelators can be used to cancel out the phase distortions introduced in the Fresnel zone.

Allowance is made for the influence of the spatial inhomogeneity of the active medium and radiation field on the output power of a laser in the form of homogeneously and inhomogeneously broadened TEM₀₀ mode lines. A calculation carried out subject to this allowance makes it possible to determine the optimal values of the transmission coefficients of the resonator mirrors and of the degree of occupancy of the active medium by the laser field. It is shown that the inhomogeneities of the active medium and field reduce the efficiency of energy conversion. The calculations are supported by the results of an experimental test carried out on an He-Ne laser (λ=632.8 nm).

An investigation was made of the stimulated emission from an electron-beam-excited HF chemical laser utilizing F₂–H₂–SF₆ and SF₆–H₂ mixtures. Conditions for increasing the efficiency of conversion of the pump energy into laser radiation were investigated. A considerable increase in the output energy was obtained on application of an external electrostatic field.

It is proposed to prepare very pure materials by combining the selective dissociation of moleculues in the gaseous phase, under the action of high-power resonant infrared radiation transforming impurities into other chemical compounds, with the removal of these compounds by conventional purification methods. By way of example, an investigation was made of the dissociation of 1,2-dichloroethane and carbon tetrachloride in mixtures with arsenic trichloride. The measured dissociation rates were found to be independent of the impurity concentration and total pressure in the mixture. The composition of the final dissociation products was determined and it indicated that the method could be used to purify arsenic trichloride.

A description is given of a cw gasdynamic laser utilizing the products of combustion of a benzene-air mixture. Values of the gain are reported in the temperature range 850 1700°K at a pressure of ~30 atm. The experimental results are compared with calculations and with earlier experiments on CO–H₂ mixtures (carried out using the same apparatus).

It is shown that the radiation pressure in the field of oppositely directed quasiresonant optical photon fluxes may produce a very narrow peak (of width less than γ/k) in the atomic velocity distribution function and this may happen in a time of ~10^–6 sec. The position of this peak is governed by the photon detuning. When the detuning is large, the velocity distribution function remains Maxwellian during the cooling of a gas. A potential use of this effect in spectroscopy is discussed.

An investigation was made of the stability of stimulated emission from a fast-flow CO₂ laser in which the active medium traveled at right-angles to the optic axis of the resonator. Amplitude modulation of the output radiation was observed in stable and unstable resonators. This modulation could not be explained by fluctuations of the gain at the entry to the resonator.

A method was developed for stabilizing the emission frequency of a ring laser operating in the two- and three-mode emission regimes with frequency splitting between the opposite waves. In this method, the mode positions were symmetric relative to the center of the gain profile in the two- or three-mode-locked regimes and then the signal representing the interference between the opposite waves had its minimum value. The depth of the minimum was optimized by suitable selection of the difference between the lengths of the interferometer arms. An experimental check of this method was made in the two- and three-mode regimes. This check demonstrated the feasibility of the method and its considerable advantages compared with the stabilization based on the power maximum.

It is proposed that the velocity of light be compared at two frequencies using the radiation of a laser with a narrow spectrum and its harmonic. If the velocities of light at these frequencies are not equal, the corresponding wavelengths are not exact multiples. Therefore, a comparison of the wavelengths—which can be made using a Fabry–Perot interferometer—can give information on the relative difference between the velocities (Δc/c). The use of radiation with a spectral width of Δν/ν~10^–11 and of an interferometer with a 3-m base should make it possible to detect Δc/c=10^–11.

A description is given of a fast-flow open-cycle CO₂ laser utilizing a mixture of atmospheric air and carbon dioxide at pressures of 40–100 Torr. The results are given of measurements of the output radiation power as a function of the air humidity, CO₂ concentration, and power supplied to the discharge chamber.

Trigger systems (flip-flops) with double and single inputs, laser multivibrator, and a laser univibrator (single-shot multivibrator) were investigated experimentally. These systems were based on a two-resonator semiconductor laser with strong optical coupling.

An analysis is made of the influence of the information carrier nonlinearity on the density of information recorded in a discrete manner in optical memories. It is shown that the use of nonlinear and threshold light-sensitive materials as information carriers can increase the recording density and the signal/noise ratio in the reproduction of the recorded information. It is reported that information can be recorded at a density of 10⁸ bit/cm² by helium-neon laser radiation in a nonlinear light-sensitive material based on a chalcogenide glass.

Plasma was formed by focusing neodymium laser radiation of 5 GW power on solid targets made of elements between Fe and Br. Radiative transitions of the 2s²2p^t–2s²2p^t+1 type were recorded for F-, O-, and N-like ions as well as spectral lines or anomalous intensity due to 4f–5g transitions in Na-like ions. Intercombination transitions in O-like ions Fe XIX, Ni XXI, Cu XXII, and Zn XXIII were observed.

An analysis is made of the propagation of 2π pulses in an amplifying medium exhibiting polarization relaxation and nonresonant linear losses. It is shown that the combined influence of such relaxation and losses may stabilize 2π pulses. Changes in the pulse parameters and their asymptotic values are considered. The distance in which there is a characteristic change in the pulse parameters is estimated for ruby laser radiation.

A new class of lasing dyes—ketocyanines—is considered. A special feature of these dyes is a large Stokes shift (3000 cm^–1) between the stimulated emission (luminescence) band and the absorption spectrum, which can be explained by a considerable increase in the strength of the hydrogen bond in the excited state. A report is given of an investigation of the lasing characteristics of ketocyanines and their mixtures with rhodamine 6G pumped with the second harmonic of a neodymium laser in a nonselective resonator. The emission range of such mixtures covers 560–640 nm, i.e., it extends over 80 nm and the individual range of emission of each of the dyes is 15–20 nm. The conversion efficiency is found to decrease with rising density of the pump radiation.

Measurements were made of the ratio of the luminescence energies represented by the ⁴I_11/2–⁴I_13/2 and ⁴I_11/2–⁴I_15/2 transitions in Er³⁺ ions in (Y_1–xEr_x)₃Al₅O₁₂ crystals. The Einstein coefficients of these transitions were also determined. The cross section of the ⁴I_11/2–⁴I_13/2 (X₂–Y₆) stimulated emission transition was measured. The concentration dependences of the absolute quantum efficiencies of the luminescence from the ⁴I_11/2 and ⁴I_13/2 levels were obtained.

A calculation is made of the effective thicknesses for modes in a diffused waveguide and their dependences on the structure parameters are obtained. The transverse distribution of the refractive index deduced from the experimental values of n^*_m is used in plotting the dispersion curves of the E and H waves in a diffused waveguide.

It was confirmed experimentally that an elastic wave could transform into a shock wave. This process resulted in a sharp increase in the number of defects in the crystal lattice. The example of molybdenum, whose (100) surface interacted with Q-switched ruby laser radiation, was used to demonstrate that a defect-concentration maximum occurred at a depth corresponding to a considerable distortion of the front of a stress wave generated by the laser radiation and to its conversion into a shock wave. The position of this maximum was in good agreement with the theory. A criterion of the possibility of formation of a shock wave was derived for the interaction with laser and other radiations.

An analysis is made of the possibility of using lasers in experimental studies of the scattering of photons by photons in vacuum. The minimum energy of each of the two lasers, required by the experimental conditions, is ~3×10⁸ J for ultraviolet radiation if the pulse duration is 5×10^–13 sec and the laser beams have the diffraction-limit divergence. The parameters obtained in this analysis indicate that the great experimental difficulties are likely to be encountered. A possibility is studied also of the formation with the aid of lasers of x- or γ-ray pulses which would collide in vacuum. It is shown that it would be much more convenient to use γ rays because it would then be sufficient to use laser systems with an energy of ~10⁶ J per pulse and the requirements to be satisfied by such pulses would be less stringent than in the optical wavelength range.

The results are reported of an investigation of the appearance of an emf in ferromagnetic and some paramagnetic metals subjected to a magnetic field and laser radiation pulses.

Efficient parametric conversion of single ultrashort light pulses in an LiIO₃ crystal was achieved. The parametric signal energy reached 200 μJ when the crystal was pumped with the second harmonic of a mode-locked YAG:Nd³⁺ laser. The wavelength of this signal could be tuned continuously in the range 0.66–2.75 μ. A Pikokhron image converter was used to show that the duration of the parametric signal decreased considerably to 2–3 psec, which was much less than the duration of the pump pulses.

The results are given of an investigation of the generation of the second harmonic of a neodymium laser in 33 new organic crystalline powders. Ways of a possible search for and synthesis of nonlinear organic materials, and their potential applications are considered.

Gas-discharge XeF, XeCI, and KrF lasers, emitting ultraviolet radiation, were constructed. Stimulated emission from a discharge in XeCI (λ₁ = 3081.6 Å, λ₂ = 3079.2 Å) was observed for the first time. The emission spectra of the lasers were determined and a structure was found in the XeF laser spectrum (six lines in the 3487.5–3585.4  range). The energy per pulse was 2, 1, and 0.5 mJ and the duration of the laser pulses was 15, 10, and 17 nsec for XeF, XeCI, and KrF lasers, respectively.

A proposal is made for an experiment in which nonlinear optics and laser spectroscopy methods are used to increase by several orders of magnitude the precision of a quantitative criterion characterizing the absence of a frequency dispersion of the Planck constant.

A review is given of the nonlinear optical properties of 20 uniaxial crystals: KDP, DKDP, ADP, CDA, DCDA, RDA, RDP, LiIO₃, LiNbO₃, Ag₃AsS₃, Ag₃SbS₃, AgGaS₂, AgGaSe₂, ZnGeP₂, CdGeAs₂, GaSe, CdSe, HgS, Se, Te. Typical applications of these crystals are indicated.

The results are reported of a theoretical and experimental investigation of the influence of resonance radiation trapping on the Zeeman effect in a ring laser. The experimentally observed strong dependence of the Zeeman beat frequency on the radiation intensity can be explained in a natural manner if allowance is made for the radiation trapping. This dependence provides a convenient means for determining the constants characterizing the influence of radiation trapping on the operation of gas lasers.

A numerical analysis is made of the field structure in a telescopic resonator of a laser with an optically inhomogeneous active medium. The amplitudes and phases of two opposite waves are calculated. The angular distribution diagrams are deduced for a variety of inhomogenities.

A theoretical analysis is made of the methods for control of the frequency spectrum of laser radiation on the basis of conversion of the frequency dependence of the refractive index of the active medium into the frequency dependence of the losses. The conversion is made by rotation of the plane of polarization (Faraday effect) or by phase anisotropy established in the active medium. The formalism of the Jones matrices is used to obtain the dependence of the losses on the angle of rotation of the plane of polarization or on the degree of phase anisotropy in some specific cases. A calculation is reported of the frequency dependence of the losses within the Voigt gain profile with specific parameters. Experimental results obtained for He–Ne lasers emitting at λ=3.39 and 0.63μ, support the usefulness of these methods in frequency selection and narrowing of the emission spectrum.

The growth of a giant pulse in a laser with an unstable resonator is analyzed by solving numerically the integral equation for an open resonator using information on the state of the active medium. A study is made of the way in which the temporal and spatial characteristics of the output radiation are affected by inhomogeneity of the excitation of the active medium and nonuniformity of the depletion of the population inversion in a transverse cross section during stimulated emission. It is shown, that in contrast to lasers with stable resonators, for certain parameters of an unstable resonator it is possible to obtain output radiation which has characteristics close to those of single-mode emission.

An investigation was made of local radiative properties of cadmium sulfide tingle crystals subjected to a variety of surface treatments. The investigation was carried out using a scanning electron microscope and apparatus for recording the cathodoluminescence spectra of various parts of a crystal of size was governed by the electron beam diameter (2–10μ). All the investigated crystals emitted luminescence in the exciton part of the spectrum (λ = 495–505 nm) and in the red band region (λ = 680–750 nm) at T= 130°K. When the surface was subjected to mechanical polishing, the red band predominated over the exciton luminescence. A local inhomogeneity of the cathodoluminescence, observed most clearly in the exciton part of the spectrum, was exhibited by all samples irrespective of the surface treatment.

It is shown that a population inversion occurs for three types of transition in neon-like ions with Z~7–15 in a steady-state plasma. A steady-state gain of ~100 cm^–1 may be expected for the 2p⁵3p¹S₀→2p⁵3S¹P₁ transition in the wavelength range λ~40–80nm. Radiation trapping by the 2p⁶→2p⁵3S and 2p⁶→2p⁵3d transitions alters drastically the gain.

A report is given of the development of a laser interferometer with a spatial resolution of 15–30μ. designed to measure waviness and deviations from the desired shape of surfaces with class 11–14 finish. Profilograms of various objects are given. The influence of destabilizing factors on the precision of the measurements is analyzed.

A system of equations describing the heating of a high-pressure gas by a high-current relativistic electron beam is solved numerically, together with a system describing a nitrogen molecular pulse laser. Quasilinear theory of the dissipation of the electron beam energy in a dense gas is used. Optimal pumping conditions are considered. The results predicted by the model are compared with the experimental data.

The process of evaporation of isolated water drops by monochromatic radiation of 10.63μ wavelength is investigated by numerical methods. The time dependences and values of the parameters describing completely the evaporation process are determined. The influence of the density and temperature discontinuities at the drop surface is considered. The effects of the evaporation coefficient and of the temperature of the ambient medium on the evaporation of a water drop in the diffusion regime are discussed.

Fast-response uncooled far-infrared detectors were developed on the basis of the photon drag of carriers in semiconductors. The responsivity, time resolution, and noise immunity of these detectors were investigated from the point of view of optimization of these parameters. Detectors without (type FP) and with (type FPU) amplifiers were built and described. These were characterized by a high time resolution (≥7×10^–10 sec), a wide power range (10–4×10⁸ W), and a high degree of noise immunity. The detectors were calibrated for CO₂ laser radiation. Two models with amplifiers (type FPU-50 and FPU-100) had a set of interchangeable detectors, which made it possible to measure radiation powers from 10 to 2×10⁶ W with the same instrument.

A description is given of a holographic measuring system including an ion gas laser, a universal holographic unit, a converter of optical information to a form suitable for a computer, and an output unit. The system is designed for tasks in experimental mechanics. Typical interferograms and the results of their analysis are given.

Uniaxial barium nitrite crystals were grown from an aqueous solution and the dispersion of the ordinary and extraordinary refractive indices was determined in the wavelength range 0.44–1.15μ. It was found that the phase-matching conditions could be satisfied in this crystal for generation of the second harmonic of the radiation emitted from a YAG:Nd³⁺ laser. The nonlinear coefficient of barium nitrite (BN) was determined relative to the nonlinear constant of lithium iodate (LI): d₃₁^BN=(0.16±15%)d₃₁^LI. The spectra of the parametric scattering of light by polaritons were determined when these crystals were excited with argon laser radiation. The scattering spectra included a manifestation of the polariton Fermi resonance. The main features of these spectra were interpreted.

The example of two types of pump beam in the quasioptics approximation is used to investigate the spatial characteristics of the radiation in stimulated Brillouin scattering. The conditions are formulated under which the scattered radiation reproduces the amplitude and phase profiles of the pump beam.

An experimental investigation was made of the characteristics of a coaxial flashlamp and of the parameters of a neodymium glass laser pumped by this lamp. The use of such a lamp in pumping an active element 45 mm in diameter and 920 mm long made it possible to obtain laser pulses of 250 μsec duration and 660 J energy with an efficiency of 3.3%. Increase of the pulse duration raised the maximum laser energy and efficiency.

A detailed theoretical analysis is made of the operation of an x-ray spectrograph with a spherical crystal analyzer in two types of task encountered in laser plasma research: measurement of the line profiles, and determination of the position of lines in a wide spectral range. It is shown that in the profile measurements the luminosity of a spectrograph with a spherical crystal can be more than an order of magnitude higher than the luminosity of a spectrograph with a cylindrical crystal. The results are reported of an experimental study in which a spectral resolution of λ/Δλ~2×10⁴ was achieved. The high luminosity of the spectrograph made it possible to record the expansion of a plasma jet at a distance of several millimeters from the target surface using just one laser flash of energy amounting to a few joules.

It is shown that the probabilities of transitions from the ground to highly excited vibrational states of a molecule depend strongly on the binding energy and atomic masses. An analysis is made of the possibility of using this effect in selective photodissociation of molecules of different isotopic compositions.

The energy characteristics of a three-dimensional solid-state laser with a telescopic resonator are investigated by solving numerically the radiative transfer equations and the population inversion equation. It is assumed that external pumping of the active medium is strongly inhomogeneous inside the resonator. The optimal values of the gain and reflection coefficient, ensuring the maximum output, are found.