Showing papers in "Quantum Electronics in 2000"
TL;DR: In this paper, the authors considered two-level resonance and quasi-resonance systems and derived the time dependence of the electric field strength in the explicit form for arbitrarily short electromagnetic pulses, without any assumptions concerning a harmonic carrier wave or the variation rate of the field in such pulses.
Abstract: Some cases of model media considered in this paper allow analytical solutions to nonlinear wave equations to be found and the time dependence of the electric field strength to be determined in the explicit form for arbitrarily short electromagnetic pulses. Our analysis does not employ any assumptions concerning a harmonic carrier wave or the variation rate of the field in such pulses. The class of models considered includes two-level resonance and quasi-resonance systems. Nonresonance media are analysed in terms of models of anharmonic oscillators — the Duffing and Lorentz models. In most cases, only particular solutions describing the stationary propagation of a video pulse (a unipolar transient of the electric field or a pulse including a small number of oscillations of the electric field around zero) can be found. These solutions correspond to sufficiently strong electromagnetic fields when the dispersion inherent in the medium is suppressed by nonlinear processes.
105 citations
TL;DR: In this article, spontaneous Raman spectroscopy of alkaline-earth tungstate crystals was performed and the frequency of the modes active in stimulated Raman scattering (SRS) modes was found to increase and their width to decrease with increasing cation radius and mass.
Abstract: Results on spontaneous Raman spectroscopy of alkaline-earth tungstate crystals are presented. The frequency of the modes active in stimulated Raman scattering (SRS) modes was found to increase and their width to decrease with increasing cation radius and mass in the series of alkaline-earth (Ca, Sr, Ba) tungstates. High peak values of the Raman scattering cross section for barium and strontium tungstate crystals — new media offering promise for SRS — were predicted and observed in the experiments. Laser experiments on the SRS threshold showed that the SRS gain for the barium tungstate crystal was close to the record value observed for the barium nitrate crystal, which is extensively used in SRS.
85 citations
TL;DR: A brief review of recent advances in the studies of two coupled three-wave nonlinear optical processes with multiple frequencies, which possess a number of special properties compared to conventional threewave processes, is presented in this paper.
Abstract: A brief review of recent advances in the studies of two coupled three-wave nonlinear optical processes with multiple frequencies, which possess a number of special properties compared to conventional three-wave processes, is presented. The consecutive interactions of co-propagating and counter-propagating light waves in a LiNbO3 crystal with a regular domain structure are considered. The energy exchange upon consecutive interactions of the waves with frequencies ω, 2ω and 3ω is analysed. The prospects of using consecutive nonlinear optical processes in quantum electronics and nonlinear optics are discussed.
78 citations
TL;DR: The principal spectroscopic and lasing characteristics of a Tm(15%):KY(WO4)2 crystal were investigated in this paper, where the transition cross sections, the luminescence quantum yield, and the lifetime and the nonlinear depopulation coefficient of the upper active state were also determined.
Abstract: The principal spectroscopic and lasing characteristics of a Tm(15%):KY(WO4)2 crystal were investigated The transition cross sections, the luminescence quantum yield, and the lifetime and the nonlinear depopulation coefficient of the upper active state were also determined The slope efficiency of lasing at the 1950 nm wavelength was 45% The feasibility of tuning in the spectral range 1850 — 1950 nm was demonstrated in principle
52 citations
TL;DR: In this paper, a simple optical method is proposed for the direct detection of biochemical reactions on a surface, which is insensitive to variations in the emission intensity and refractive index of a solution.
Abstract: A simple optical method is proposed for the direct detection of biochemical reactions on a surface, which is insensitive to variations in the emission intensity and refractive index of a solution. The method is based on the detection of the spectrum of reflected or transmitted emission modulated by the interference in a sensitive layer of a large thickness (several tens and hundreds of microns), which can be a microscope cover glass with a deposited receptor layer. A change in the phase of the interference pattern in this spectrum is used as an information signal about a change in the thickness of the sensitive layer caused by a biochemical reaction. The method was tested in studies of the reactions of binding and detachment of proteins in real time. The root-mean-square noise of the method expressed in the layer thickness is 3 pm.
44 citations
TL;DR: In this article, a self-initiated volume discharge (SIVD) in non-chain HF lasers with SF6-C2H6 mixtures was investigated and it was shown that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady state value.
Abstract: A self-sustained volume discharge without preionisation, i.e. a self-initiated volume discharge (SIVD), in nonchain HF lasers with SF6—C2H6 mixtures was investigated. It was established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady state value. It is shown that, as new channels appear, the current flowing through the channels formed earlier decreases. The volume occupied by the SIVD increases with increase in the energy deposited in the plasma and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously with increase in the current. The possible mechanisms which explain the observed phenomena, namely the dissociation of SF6 molecules and electron attachment SF6 molecules, are examined. A simple analytical model, which makes it possible to describe these mechanisms at a qualitative level, was developed.
42 citations
TL;DR: In this article, the properties of Bessel light beams (BLBs) in nonlinear crystals are studied theoretically and experimentally, and new possibilities and prospects of the development of methods for nonlinear optical frequency conversion using BLBs are discussed.
Abstract: The properties of frequency conversion of Bessel light beams (BLBs) in nonlinear crystals are studied theoretically and experimentally. New possibilities and prospects of the development of methods for nonlinear optical frequency conversion using BLBs are discussed. The second harmonic generation (SHG) is studied under the conditions of critical and noncritical phase matching. The longitudinal and transverse phase matching is analysed in detail upon SHG and sum frequency generation in BLBs. The concept of azimuthal width of phase matching caused by the longitudinal and transverse wave detuning is introduced, and its value is calculated for collinear and π-vector interactions. The regime of azimuthally matched interactions is selected, which is realised when the azimuthal phase matching width is small. A correlation of the azimuthal BLB components caused by these interactions is predicted. It is shown that azimuthally matched BLBs are characterised by a significant increase in the overlap integral and by nonlinear interactions that do not destroy their spatial structure.
26 citations
TL;DR: In this paper, the appearance and development of large-scale self-organising microstructures on the surface of monocrystalline Si and several other materials (Ge, Ti) were studied upon their evaporation by 20-ns pulses from a copper vapour laser at 510.6 nm.
Abstract: The appearance and development of large-scale self-organising microstructures on the surface of monocrystalline Si and several other materials (Ge, Ti) are studied upon their evaporation by 20-ns pulses from a copper vapour laser at 510.6 nm. The structures were formed upon repeated pulsed laser irradiation (~104 pulses with an energy density of 1–2 J cm-2) in the absence of optical breakdown of the medium above the target surface in the 1–105 Pa pressure range in a wide range of angles of laser radiation incidence on the surface. The structures are cones with an apex angle of ~20–25°, which grow towards the laser beam. It is shown that the spatial period of the structures developing during laser evaporation is determined by the period of the waves arising on the melt surface and is equal to 10–20 μm. The x-ray diffraction analysis showed that the modified substrate region has a polycrystalline structure and consists of crystallites with dimensions ranging from 40 to 70 nm, depending on the pressure of the ambient atmosphere.
26 citations
TL;DR: In this article, the authors demonstrated experimentally that at high average radiation power, the optical isolation in the recently proposed design of a Faraday isolator is substantially higher than in the conventional scheme.
Abstract: It is demonstrated experimentally that at high average radiation power, the optical isolation in the recently proposed design of a Faraday isolator is substantially higher than in the conventional scheme. The Faraday isolator with the isolation of 45 dB at the radiation power of 100 W is implemented. The data obtained show that a 30-dB isolator for the average laser radiation power of 1 kW can be realised.
25 citations
TL;DR: In this paper, the potentialities of aperiodic multilayer structures (AMSs) optimised to obtain a preassigned reflection spectrum in the x-ray range (λ < 300 A) and also starting from other criteria were investigated.
Abstract: An investigation was made of the potentialities of aperiodic multilayer structures (AMSs) optimised to obtain a preassigned reflection spectrum in the x-ray range (λ < 300 A) and also starting from other criteria. It was found that among the multitude of realisations of AMSs there exist those which are superior to the regular structure in width of the operating range, integral reflectivity, and peak reflectivity. New types of x-ray optical elements are proposed on a basis of AMSs. AMSs were derived which possess a constant normal-incidence reflectivity R at normal incidence throughout the 130 — 190 A (R=24 %), 130 — 300 A (R=15%), etc., ranges. We found AMSs which possess a high polarising power (polarisance) and a constant R in a broad wavelength range for a fixed angle of incidence. AMSs possessing several isolated reflection peaks which are not Bragg peaks of one another, were calculated. AMSs intended for operation in the hard x-ray range at grazing incidence of radiation were optimised. The technique elaborated in our work was demonstrated to be efficient for optimising AMSs with a very large (~103) number of layers.
25 citations
TL;DR: In this article, the main physical principles of the operation of ring gas laser in the laser-gyroscope regime are examined, and the influence of non-reciprocal effects on the operational parameters of the ring gas lasers and the methods of controlling, with the aid of the non-receptive magneto-optical Zeeman effect, the parameters of these lasers used in gyroscopes are discussed.
Abstract: The main physical principles of the operation of ring gas lasers in the laser-gyroscope regime are examined. The influence of nonreciprocal effects on the operational parameters of ring gas lasers and the methods of controlling, with the aid of the nonreciprocal magneto-optical Zeeman effect, the parameters of these lasers used in gyroscopes are discussed.
TL;DR: In this article, the influence of the thermal self-interaction of the laser radiation in the first pass through a Faraday isolator on the power losses in the main spatiopolarisation mode is analyzed.
Abstract: The influence of the thermal self-interaction of the laser radiation in the first pass through a Faraday isolator on the power losses in the main spatiopolarisation mode is analysed. Analytical expressions for these losses were obtained for different designs of the isolators. It is shown that the design with two 22.5° Faraday rotators and with a 67.5° reciprocal rotator between the former devices is best from the standpoint of all the isolator parameters. The results obtained for a Gaussian beam were extended to the case of super-Gaussian and Π-shaped (step-like) beams. It was established that the Π-shaped beam exhibits a minimal self-interaction.
TL;DR: In this paper, near and far field patterns are studied for powerful (above 2-W cw output) quantum-well heterojunction InGaAs/AlGaA/GaAs lasers.
Abstract: Near- and far-field patterns are studied for powerful (above 2-W cw output) quantum-well heterojunction InGaAs/AlGaAs/GaAs lasers. The maximum radiation brightness was 1.7107 W cm-2 sr-1. It is shown that the radiation filamentation is already observed 10 — 20% above the lasing threshold. The filamentation period decreases from 50 to 10 μm with increasing pumping current from almost the lasing threshold to an excess of 20% over the threshold. The filamentation results in the tenfold decrease in the radiation brightness of lasers compared to the theoretical value.
TL;DR: In this article, the first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 1017 W cm-2 in CO2 and Kr gas jet targets is reported.
Abstract: The first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 1017 W cm-2 in CO2 and Kr gas jet targets is reported. The emission in the wavelength ranges of the 1snp—1s2(n=3–6) transitions of O VII ions and the Lyα line of O VIII ions, as well as of the (2s1/22p63p3/2)1—2s22p6 1S0 and (2s1/22p63p1/2)1—2s22p6 1S0 lines of Ne-like KrXXVII ions testifies that the highly ionised plasma is formed by collision processes in clusters. Modelling the shape of the spectral lines of oxygen ions by including the principal mechanisms of broadening and absorption in optically dense plasmas reveals that the main contribution to the time-integrated intensity is made by the plasma with the parameters Ne=(2–20)×1020 cm-3 and Te=100 — 115 eV.
TL;DR: In this article, the advantages of a polyurethane matrix over other polymers, which are widely used as active media for dye lasers, are analyzed, such as photostability, service life, radiation resistance, conversion efficiency, and homogeneity of the dye distribution.
Abstract: The advantages of a polyurethane matrix over other polymers, which are widely used as active media for dye lasers, are analysed. This matrix exhibits the photostability, service life, radiation resistance, conversion efficiency, and homogeneity of the dye distribution that surpass these properties for active media based on polyurethane acrylate, which has close physical and operation properties. These advantages result not only from the milder polymerisation conditions but also from a lower probability of the formation of ion pairs and dye aggregates. A substantial suppression of these processes in polyurethane is explained by its greater polarity and solvation ability compared to polyurethane acrylate.
TL;DR: In this article, a set of diode-pumped fiber lasers producing a cw output of 4-7.5 W in the range from 1.05 to 1.15-μm is realised on the basis of an ytterbium double-cladded fiber.
Abstract: A set of diode-pumped fibre lasers producing a cw output of 4–7.5 W in the range from 1.05 to 1.15-μm is realised on the basis of an ytterbium double-cladded fibre. The output of the ytterbium fibre laser was used to pump a Raman phosphor-silicate fibre converter, resulting in fibre lasers producing a cw output power of more than 3 W at 1.26 and 1.3-μm.
TL;DR: The use of linearly chirped pulses in coherent anti-Stokes Raman scattering spectroscopy allows the spectra of nonlinear susceptibility to be studied with terahertz resolution by measuring the intensity of the signal emerging from four-wave mixing as a function of the delay time between the pump pulses as mentioned in this paper.
Abstract: We propose new schemes of high-resolution coherent four-photon spectroscopy where chirped pulses are employed for the Raman excitation of a nonlinear medium. The use of linearly chirped pulses in coherent anti-Stokes Raman scattering spectroscopy allows the spectra of nonlinear susceptibility to be studied with a terahertz resolution by measuring the intensity of the signal emerging from four-wave mixing as a function of the delay time between the pump pulses. This approach can be also employed for single-pulse spectroscopy of nonlinear susceptibility.
TL;DR: In this article, a laser ablation performed with an automated excimer XeCl laser unit is used for large surface cleaning in the context of nuclear power plant maintenance, where metal surfaces are oxidised and are representative of contaminated surfaces with radionuclides.
Abstract: The laser ablation performed with an automated excimer XeCl laser unit is used for large surface cleaning. The study focuses on metal surfaces that are oxidised and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The unit contains an XeCl laser, the beam delivery system, the particle collection cell, and the system for real-time control of cleaning processes. The interaction of laser radiation with a surface is considered, in particular, the surface damage caused by cleaning radiation. The beam delivery system consists of an optical fibre bundle of 5 m long and allows delivering 150 W at 308 nm for laser surface cleaning. The cleaning process is controlled by analysing in real time the plasma electric field evolution. The system permits the cleaning of 2 to 6 m2 h-1 of oxides with only slight substrate modifications.
TL;DR: In this article, a comparative analysis of the processes responsible for dissociation of molecular iodine in the oxygen-iodine medium is made, and the rate of relaxation of vibrationally excited oxygen in the O2I2H2O medium is shown to be limited by the VV energy exchange between oxygen and water molecules.
Abstract: The comparative analysis of the processes responsible for dissociation of molecular iodine in the oxygen-iodine medium is made. The rate of relaxation of vibrationally excited oxygen in the O2—I2—H2O medium is shown to be limited by the VV energy exchange between oxygen and water molecules, and the fraction of vibrationally excited O2 (ν=1) in the active medium of the oxygen-iodine laser can reach several tens of percent. It is noted that the VV exchange in O2(1Δ,ν=1)+I(2P3/2)↔O2(3Σ,ν=1)+I(2P1/2) reaction may be of considerable importance in the kinetics of formation of the active medium in the oxygen-iodine laser.
TL;DR: In this article, it was shown that the recent production of an ultracold laser plasma (Ne ~ 2 × 109 cm-3, Te ~ 0.1 K, Ti ~ 10 μK) can be considered as the first experimental demonstration of the metastable state of a supercooled plasma which was predicted theoretically.
Abstract: It is shown that the recent production [T C Killian et al. Phys. Rev. Lett. 83 4776 (1999)] of an ultracold laser plasma (Ne ~ 2 × 109 cm-3, Te ~ 0.1 K, Ti ~ 10 μK) can be considered as the first experimental demonstration of the metastable state of a supercooled plasma which we predicted theoretically. Our theory provides an explanation for the moderation of three-body recombination observed in the above-cited paper. We present the calculations that simulate the conditions of the ultracold-plasma experiments.
TL;DR: In this paper, a pulsed, multifrequency electroionisation CO laser operating on the first vibrational overtone of the CO molecule is studied experimentally and theoretically, and it is shown experimentally that the overtone CO laser is an efficient source of coherent radiation in the 2.5-4.1-μm region whose specific output reaches 50 J l-1 amagat-1 and the electro-optical efficiency amounts to 11 %.
Abstract: Characteristics of a pulsed, multifrequency electroionisation CO laser operating on the first vibrational overtone of the CO molecule are studied experimentally and theoretically. It is shown experimentally that a pulsed, multifrequency overtone CO laser is an efficient source of coherent radiation in the 2.5–4.1-μm region whose specific output reaches 50 J l-1 amagat-1 and the electro-optical efficiency amounts to 11 %. A theoretical analysis based on experimental data shows the feasibility of obtaining overtone emission with efficiency as high as ~20 %. The alternation of the intensity of vibrational bands in the overtone CO laser is discussed. This effect is caused by the cascade mechanism of formation of the emission spectrum. The comparison of experimental data with calculations showed that they agree well with respect to spectral and energy characteristics of the overtone CO laser. Moreover, it revealed the necessity of refinement of the kinetic model of the active medium of the CO laser for obtaining an adequate description of time parameters of a laser pulse.
TL;DR: In this paper, a simple model of a multicascade fiber Raman laser is considered and analytic expressions for its output characteristics are obtained for its performance, which is determined by the lumped optical loss of the cavity.
Abstract: A simple model of a multicascade fibre Raman laser is considered and analytic expressions are obtained for its output characteristics. The efficiency of the Raman laser is shown to be determined to a considerable extent by the lumped optical loss of the cavity. A proposal is made to estimate the quality of optical fibres as an active medium for multicascade fibre Raman lasers from the efficiency of the model Raman laser.
TL;DR: In this paper, a three-dimensional microscopy of an optical-breakdown plasma based on third-harmonic generation (THG) is experimentally implemented, which allows the transverse spatial resolution to be considerably improved as compared with conventional methods of microscopy.
Abstract: A three-dimensional microscopy of an optical-breakdown plasma based on third-harmonic generation (THG) is experimentally implemented. THG is shown to offer a universal method for three-dimensional microscopy of inhomogeneities of linear and nonlinear optical parameters of various media. Due to the nonlinear-optical character of this process, THG microscopy allows the transverse spatial resolution to be considerably improved as compared with conventional methods of microscopy. A high spatial resolution along the direction of probing is achieved due to the fact that the prohibition on THG in the regime of tight focusing is removed whenever inhomogeneities of linear and/or nonlinear optical parameters are probed by THG.
TL;DR: In this article, the properties of a nonequilibrium plasma produced by high-power laser pulses with intensities IL ≈ 1014-1015 W cm-2 irradiating plane targets made of a porous material are investigated.
Abstract: The properties of a nonequilibrium plasma produced by high-power laser pulses with intensities IL ≈ 1014—1015 W cm-2 irradiating plane targets made of a porous material are investigated. The mean density of matter in targets was substantially higher than the critical plasma density corresponding to a plasma resonance. The density of porous material was ρa ≈ 1 — 20 mg cm-3, whereas the critical density at the wavelength of incident radiation was ρcr ≈ 3 mg cm-3. An anomalously high absorption (no less than 80%) of laser radiation inside a target was observed. Within the first 3 — 4 ns of interaction, the plasma flow through the irradiated target surface in the direction opposite of the direction of the laser beam was noticeably suppressed. Only about 5% of absorbed laser energy was transformed into the energy of particles in this flow during the laser pulse. Absorbed energy was stored as the internal plasma energy at this stage (the greenhouse effect). Then, this energy was transformed, similar to a strong explosion, into the energy of a powerful hydrodynamic flow of matter surrounding the absorption region. The specific features of the formation and evolution of a nonequilibrium laser-produced plasma in porous media are theoretically analysed. This study allows the results of experiments to be explained. In particular, we investigated absorption of laser radiation in the bulk of a target, volume evaporation of porous material, the expansion of a laser-produced plasma inside the pores, stochastic collisions of plasma flows, and hydrothermal energy dissipation. These processes give rise to long-lived oscillations of plasma density and lead to the formation of an internal region where laser radiation is absorbed.
TL;DR: In this paper, a nonstationary model of radiation gas dynamics for subsonic laser-supported combustion waves is presented, and a systematic numerical simulation of the temperature and gas-dynamic structure of such waves under the conditions of experiments of E L Klosterman and S R Byron is carried out.
Abstract: A nonstationary model of radiation gas dynamics for subsonic laser-supported combustion waves is presented. A systematic numerical simulation of the temperature and gas-dynamic structure of such waves under the conditions of experiments of E L Klosterman and S R Byron is carried out. It is shown that the dominant process governing the propagation of subsonic laser-supported combustion waves in this case is the reabsorption of heat radiation ahead of the wave front, whereas the gas-dynamic processes are of minor importance.
TL;DR: In this paper, a pulsed electroionisation CO laser operating on the first overtone of the CO molecule in the frequency-selective regime was studied experimentally and theoretically.
Abstract: Lasing properties of a pulsed electroionisation CO laser operating on the first overtone of the CO molecule in the frequency-selective regime were studied experimentally and theoretically. Lasing was observed on a large number of separate vibrational-rotational transitions ν+2→ν from 13→11 to 38→36 (more than 400 spectral lines) in the spectral range from 2.7 to 4.2 μm. The specific output energy of the overtone CO laser reached ~3.0 J l-1 amagat-1, and the electrooptical conversion was ~0.6 %. The formation of emission spectra from high vibrational levels in the overtone CO laser observed for the first time is discussed. The comparison of experimental and theoretical data showed the necessity of including the multiquantum exchange on high vibrational levels into the kinetic model of the active medium of the CO laser.
TL;DR: In this paper, a comparative analysis of the dependences of the refractive index of Mg:LiNbO3 single crystals on the Mg concentration is performed in the visible and IR transparency regions.
Abstract: A comparative analysis of the dependences of the refractive index of Mg:LiNbO3 single crystals on the Mg concentration is performed in the visible and IR transparency regions. The results of measurements at the wavelengths above 4 μm suggest the four-step mechanism of incorporation of the Mg impurity to the LiNbO3 crystal in the range of molar concentrations of Mg from 0 to 7.1 %. The resonances observed between 1 and 2 μm and between 2.8 and 3.5 μm in the transparency region are interpreted as contributions from polaron states. It is shown that the resonance in the region between 1 and 2 μm is strongly enhanced in crystals with the molar concentration of Mg above 5.1%.
TL;DR: In this article, the conversion efficiency and service life of the laser elements based on a polymer-filled microporous glass (PFMPG) composite doped with organic dyes are studied.
Abstract: The conversion efficiency and service life of the laser elements based on a polymer-filled microporous glass (PFMPG) composite doped with organic dyes are studied. It is shown that both the conversion efficiency and the service life of the laser elements achieve the values obtained for the same dyes in bulk polymer elements. Good lasing characteristics of the elements studied are advantageously combined with the high mechanical strength and high laser damage resistance and excellent thermooptical properties of the PFMPG composite.
TL;DR: In this paper, it was shown that for SF6-hydrocarbon (deutero-carbon) mixtures with a composition typical for nonchain HF(DF) lasers, the electric field strength reduced to the partial pressure of SF6 in the quasistationary phase of an SSVD is close to the known critical value (E/p)cr = 89 V m−1 Pa−1, which is specified by the condition that the electron-impact ionization rate of the SF6 is equal to the rate of electron attachment to SF6 molecules.
Abstract: It was found that for SF6-hydrocarbon (deutero-carbon) mixtures with a composition typical for nonchain HF(DF) lasers, the electric field strength reduced to the partial pressure of SF6 \( (p_{{\text{SF}_{\text{6}} }} ) \) in the quasistationary phase of an SSVD \( (E/p_{{\text{SF}_{\text{6}} }} ) \) st = 92 V m−1Pa−1 is close to the known critical value (E/p)cr = 89 V m−1 Pa−1, which is specified by the condition that the electron-impact ionization rate of SF6 is equal to the rate of electron attachment to SF6 molecules. This testifies to the decisive role of these two processes and allows the use of the known approximations of the effective ionization coefficient and the electron drift velocity for pure SF6 when calculating the discharge characteristics. The oscilloscope traces of voltage and current calculated in this approximation for lasers with apertures ranging from 4 to 27 cm deviated from the experimental data by no more than 10%.
TL;DR: In this paper, a complete classification of phase-matching directions for the second-harmonic generation in biaxial crystals with quadratic nonlinearity is presented, where the phase matching direction is defined in terms of the number of phases.
Abstract: A complete classification of phase-matching directions for the second-harmonic generation in biaxial crystals with quadratic nonlinearity is presented.