Showing papers in "IEEE Journal of Quantum Electronics in 1974"
TL;DR: In this article, a review of recent experimental results on laser-induced electric breakdown in transparent optical solid materials is given, where a fundamental breakdown threshold exists characteristic for each material, which is determined by the same physical process as dc breakdown, namely, avalanche ionization.
Abstract: A review is given of recent experimental results on laser-induced electric breakdown in transparent optical solid materials. A fundamental breakdown threshold exists characteristic for each material. The threshold is determined by the same physical process as dc breakdown, namely, avalanche ionization. The dependence of the threshold on laser pulse duration and frequency is consistent with this process. The implication of this breakdown mechanism for laser bulk and surface damage to optical components is discussed. It also determines physical properties of self-focused filaments.
630 citations
TL;DR: A method for calculating induced-emission cross sections in neodymium laser glasses, based on simple absorbance measurements, has been demonstrated in this article, where the absorption and emission transition probabilities of four silicate-base NE laser glasses have been characterized in terms of the Judd-Ofelt (JO) model of crystal-field-induced electric-dipole transitions.
Abstract: A method for calculating induced-emission cross sections in neodymium laser glasses, based on simple absorbance measurements, has been demonstrated. Absorption and emission transition probabilities of four silicate-base neodymium laser glasses have been characterized in terms of the Judd-Ofelt (JO) model of crystal-field-induced electric-dipole transitions. Absolute absorption intensities in 3669A, ED-2, LSG-91H, and S33 glasses were measured and used to determine three phenomenological intensity parameters for each glass which accounted for the measured intensities to within 5 percent (rms). Emission intensities between the metastable4 F_{3/2} and terminal4 I J levels were then calculated for each glass, together with the4 F_{3/2} radiative lifetime, fluorescence branching ratios, and radiative quantum efficiency. Calculated values of these quantities for 3669A and S33 glasses are compared with measured values appearing in the literature. Using experimental line shapes for the4 F_{3/2} \rightarrow 4 I_{11/2} transitions at 1.06μ, induced-emission cross sections for these glasses were calculated.
437 citations
TL;DR: In this article, a model of a passively mode-locked quasi-continuous laser is discussed and the evolution of pulses in various cavity configurations is traced and the combined action of amplifier and absorber saturation is shown to lead to rapid pulse compression even when the pulse duration is far shorter than the relaxation time.
Abstract: Various models of a passively mode-locked quasi-continuous laser are discussed and the evolution of pulses in various cavity configurations is traced. In certain circumstances, the combined action of amplifier and absorber saturation is shown to lead to rapid pulse compression even when the pulse duration is far shorter than the relaxation time of either nonlinear component. The results are in good agreement with recent streak- camera measurements involving the pulsed Rhodamine 6G dye laser and satisfactorily explain the efficient generation of picosecond pulses in CW dye-laser systems. The same pulse-compression mechanism can probably be used to generate ultrashort pulses in other quasi-continuous lasers.
266 citations
TL;DR: In this article, the authors analyzed the laser threshold condition of thin-film Bragg-reflector (DBR) and distributed-bragg reflectors (DBR) waveguides with various waveguide structures.
Abstract: Wave propagation in periodic waveguides is analyzed by decomposing the eigen Bloch waves into traveling-wave components. It is shown that the principal components consist of a primary forward wave, a primary backward wave, and their Bragg-scattered secondary waves. One important parameter is the coupling constant s due to Bragg scattering, which relates the secondary wave to the respective primary wave. Laser threshold condition is then obtained by applying the continuity of tangential E and H at the two boundaries. The results thus obtained are general and applicable to thin-film lasers with various waveguide structures. The laser threshold condition of thin-film Bragg lasers is expressed in terms of two effective reflection coefficients for easy comparison with conventional lasers. For appreciable reflection, a significant change either in the propagation constant or in the coupling constant is required. Two basic types of thin-film Bragg lasers are distributed-feedback (DFB) lasers in which Bragg scattering is confined to the active medium and distributed-Bragg-reflector (DBR) lasers in which Bragg scattering is limited to regions beyond the active medium. The threshold gain, frequency control, and mode selectivity for both types are analyzed and the analyses are applied to GaAs and Nd lasers. It is shown that DBR lasers should have a lower threshold gain and a better mode selectivity than DFB lasers. For distributed-feedback effect to play a significant role in thin-film Bragg lasers, the product kL int must be greater than unity where K is the distributed-feedback coefficient and L int is the interaction length. Advantages for having periodic structures outside the active medium so as to relax constraints on k and L int are also discussed.
250 citations
TL;DR: In this article, a novel type of optical fiber which is composed of three portions: the core, inner cladding, and outer cladding was investigated, and it is assumed that the core has the largest refractive index of the three, and the outer claddings index is the next largest.
Abstract: This paper investigates a novel type of optical fiber which is composed of three portions: the core, inner cladding, and outer cladding. It is assumed that the core has the largest refractive index of the three, and the outer cladding index is the next largest. When the index difference between the core and the inner cladding is much larger than that between the outer cladding and the inner, the new fiber has a stronger confinement property than a usual singly clad fiber in the single-mode region. It is also assumed that the inner-cladding thickness is larger than or comparable with the core radius. This confinement is the origin of the following three properties of potential importance in single-mode optical communication. 1) As compared with a singly clad fiber, the largest core area for single-mode operation is roughly twice. 2) The group delay arising from waveguide characteristics has an opposite sign against that of typical glass dispersion. (Singly clad fiber has a dispersion of the same sign.) 3) The field is much more tightly confined within the core as compared with a singly clad fiber. This minimizes extra attenuation due to absorption in the cladding.
239 citations
TL;DR: In this paper, an original frequency-mixing technique is described which conveniently measures the third-order optical susceptibility of any transparent material, and the results are presented for χ1111(3), ω1, ω 1, and ω 2 in a number of materials.
Abstract: An original frequency-mixing technique is described which conveniently measures the third-order optical susceptibility of any transparent material. Results are presented for χ1111(3)(-ω3, ω1, ω1, -ω2) in a number of materials. These measurements permit estimates of the nonlinear index n2.
121 citations
TL;DR: In this paper, the conditions for population inversion between the C−3πu and B−πu levels (πu = 3371 A) of N 2 such as the excitation time and the optimum value of E/p are calculated.
Abstract: The conditions for population inversion between the C^{3}\Pi_{u} and B^{3}\Pi_{g} levels ( \lambda = 3371 A) of N 2 such as the excitation time and the optimum value of E/p are calculated. To meet the required conditions for a very fast population inversion, we describe a traveling wave laser structure which is very simple. We study the experimental curves of the laser power as a function of the following parameters: channel length, pressure, distance between electrodes, velocity matching between excitation traveling wave pulse and light, and spark gap breakdown voltage. Best results obtained to date are a peak power of 9 MW with a total efficiency of about 1 percent and a ratio E/p\simeq 200 V/cm. torr.
87 citations
TL;DR: In this paper, the third-order electronic susceptibility has been specialized to some model systems in order to evaluate the associated nonlinear refractive index of solid materials, and it was found that the dominant positive contribution involves oscillator strengths connecting excited electronic levels.
Abstract: The general theory of the third-order electronic susceptibility has been specialized to some model systems in order to evaluate the associated nonlinear refractive index of solid materials. The results indicate oppositely signed terms of comparable magnitude, and it is found that the dominant positive contribution involves oscillator strengths connecting excited electronic levels. Some reported values of the nonlinear index n 2 for various glasses are discussed in relation to the model calculations.
82 citations
TL;DR: A review of the status and properties of coherent sources of ultraviolet radiation is presented in this article, which includes a wide range of developments concerning atomic and molecular systems useful for generating wavelengths below 4000 A, as well as progress in alternative methods of ultraviolet production.
Abstract: A review of the status and properties of coherent sources of ultraviolet radiation is presented. This includes a wide range of developments concerning atomic and molecular systems useful for generating wavelengths below 4000 A, as well as progress in alternative methods of ultraviolet production. Particular emphasis is placed on recent advances in molecular bound-free systems whose operation is enhanced at high densities. It is believed that some of these systems may be scalable to sufficiently high-energy outputs to be useful in controlled fusion applications. A brief prognosis and discussion of future developments tending to the X-ray region are given.
69 citations
TL;DR: In this paper, tungsten-nickel point contact diodes, when used as harmonic-generator mixers, were measured and the measured properties are those which will be useful to workers wishing to use these high-speed devices (faster than 10-14s).
Abstract: Properties of tungsten-nickel point contact diodes, when used as harmonic-generator mixers, were measured. The measured properties are those which will be useful to workers wishing to use these high-speed devices (faster than 10-14s). Some of the properties measured were : the decrease in signal with mixing order; the detected signal as a function of laser frequency; and the power required to optimize the harmonic beat notes.
67 citations
TL;DR: In this paper, the effect of selected additives on photoionization was demonstrated and the results showed that a significant enhancement in electron density can be achieved, and the X-band microwave interferometer data provided additional insight into the mechanisms involved and further substantiated the effectiveness of the technique in high-powered CO 2 laser design.
Abstract: Measurements of UV photoionization parameters for TEA CO 2 gas lasers are presented. Electron density and ionization decay times are given as a function of pressure for several gases and gas mixtures. Penetration depth of ionizing radiation in the gases is determined. The effect of selected additives on photoionization is demonstrated. The results show that a significant enhancement in electron density can be achieved. The X -band microwave interferometer data provide additional insight into the mechanisms involved and further substantiate the effectiveness of the technique in high-powered CO 2 laser design.
TL;DR: In this article, the authors investigated the tunability of the 2-μ laser emission from Ho3+ in BaY 2 F 8 and showed that it can be explained by oscillation in transverse modes of the resonator.
Abstract: Infrared spontaneous and stimulated emission from Ho3+in BaY 2 F 8 is reported. In addition to the familiar5 I_{7} \rightarrow 5I 8 transition at 2 μ,5 F_{5} \rightarrow 5I 5 emission at 2.4μ and5 I_{6} \rightarrow 5I 7 emission at 2.9μ are discussed. There are several unusual features of the 2-μ laser emission. At room temperature, phonon-terminated laser emission is observed at 2.171 μ. At 77 K a complex CW laser output is observed in a wavelength interval lying on the shoulder of a fluorescence line. The complex output is attributed to oscillation in transverse modes of the resonator. Oscillation is not observed in the strongest emission line, despite a large terminal state splitting of 310 cm-1. These results are explained on the basis of a theory developed earlier for transition metal ion lasers. The validity of the model is supported by demonstrating the tunability through loss modulation predicted by theory. The observation of these effects is made possible by the very low internal scattering loss in the crystals. The5 F_{5} \rightarrow 5I 5 laser lines near 2.4 μ represent relatively low gain transitions with pulse durations limited by accumulation in a longer lived terminal state. The dynamics of laser emission indicate the possible absence of thermal equilibrium in the excited state. For the 2.9-μ transition the bottleneck posed by a longer lived terminal state may be eliminated by the addition of Eu3+or Pr3+, but laser emission could not be obtained.
TL;DR: In this article, a birefringent filter which is suitable for tuning dye lasers having high gain is described. Transmission and tuning characteristics for the filter are calculated and several appropriate designs having small sidebands, a minimum number of elements, and narrow passbands are discussed.
Abstract: A birefringent filter which is suitable for tuning dye lasers having high gain is described. Transmission and tuning characteristics for the filter are calculated. Several appropriate designs having small sidebands, a minimum number of elements, and narrow passbands are discussed.
TL;DR: In this article, a self-focusing theory based on linear stability analysis of the quasi-optical equation was proposed for beams of finite aperture, which may be initially convergent or divergent.
Abstract: In a recent paper the author proposed a self-focusing theory based on linear stability analysis of the quasi-optical equation [1]. Strictly, the theory applies only to a plane wave of infinite aperture. In this paper the theory is extended to beams of finite aperture, which may be initially convergent or divergent.
TL;DR: In this article, the concept of mode stability is considered in detail and a procedure is developed for determining the stability of laser resonators and optical waveguides containing arbitrary lens elements.
Abstract: The concept of mode stability is considered in detail and a procedure is developed for determining the stability of laser resonators and optical waveguides containing arbitrary lens elements. It is found that under some conditions the addition of a laser medium with a gain profile makes oscillation or propagation impossible in an otherwise stable system. A new formalism is described for the propagation of off-axis modes.
TL;DR: In this paper, a high-pressure electrical discharge that employs volumetric photoionization of the gas by ultraviolet radiation was investigated, and the discharge was operated in a self-sustained mode at high values of energy input for several microseconds duration.
Abstract: Investigations of a moderate-volume high-pressure electrical discharge that employs volumetric photoionization of the gas by ultraviolet radiation are reported. Operation of the discharge in a self-sustained mode at high values of energy input for several microseconds duration has been achieved. Use of the method in a pulsed electrical CO 2 -laser configuration has yielded an optical energy extraction of 40 J/1 atm at a conversion efficiency of 24 percent. Experiments related to the physics of the photoionization process and parametric behavior of the discharge and laser are described.
TL;DR: In this paper, the room temperature cross sections for the Nd3+4 F 3/2 levels to the 4 I 11/2 and 4 I 9/2 manifolds (lower laser state and ground state, respectively) were measured by two spectroscopic methods.
Abstract: The room-temperature cross sections for the Nd3+4 F_{3/2} levels to the4 I_{11/2} and4 I_{9/2} manifolds (lower laser state and ground state, respectively) in NdP 5 O 14 are measured by two spectroscopic methods. A value for the largest cross section of \sigma(R_{1} - Y_{2}) = 1.7 \times 10^{-19} cm2is found. The highest effective cross section, resulting from superposition of two lines at 1.051 μm, gives a laser gain per Nd ion which is about 2/3 of the maximum gain in YAG:Nd. The relative branching ratio into the4 I_{11/2} and4 I_{9/2} manifolds is 0.65:0.35. Comparison of the integrated cross sections with the measured lifetime for 1-percent Nd in LaP 5 O 14 indicates a combined efficiency I_{13/2} and4 I_{15/2} manifolds and multiphonon quenching. A measurement of temperature dependence of fluorescence lifetime supports this last result.
TL;DR: In this paper, a peak laser power of 0.5 MW with an estimated efficiency of 1.2 percent has been obtained at 3577 A from a mixture of 92 psia Ar and 8 psia N 2 which was excited by an E -beam of 400 A/cm2 at 1.3 MeV in a 20-ns pulse.
Abstract: A peak laser power of 0.5 MW with an estimated efficiency of 0.2 percent has been obtained at 3577 A from a mixture of 92 psia Ar and 8 psia N 2 which was excited by an E -beam of 400 A/cm2at 1.3 MeV in a 20-ns pulse. A saturation intensity of ∼100 kW/cm2was deduced and a beam divergence of 10 mrad was measured from the laser having a 10-cm gain length.
TL;DR: In this paper, the absorption properties of silver thiogallate have been investigated and the results on the refractive indices of the material have been incorporated into sets of Sellmeier expressions.
Abstract: New measurements are presented on the absorption of silver thiogallate and related to fundamental mechanisms. All available data on the refractive indices of silver thiogallate, including new results for the visible, have been incorporated into sets of Sellmeier expressions. Different Sellmeier constants are given for visible and infrared wavelengths and also for crystals from different sources. Confirmation of some predictions from these Sellmeier expressions has been obtained by second-harmonic generation (SHG) experiments with a tunable optical parametric oscillator. Preliminary results on laser damage are summarized.
TL;DR: In this paper, the gain coefficient of a TEA double-discharge CO 2 laser versus wavelength was measured, and it was shown that while the overall wavelength dependence is in good agreement with that predicted from the model wherein the rotational levels are in thermal equilibrium, P(20) in the 10.4-μm band and P(22), in the 9.4m band have a gain coefficient that is ∼10 percent high.
Abstract: Direct measurements of the gain coefficient of a TEA double-discharge CO 2 laser versus wavelength show that while the overall wavelength dependence is in good agreement with that predicted from the model wherein the rotational levels are in thermal equilibrium, P(20) in the 10.4-μm band and P(22) in the 9.4-μm band have a gain coefficient that is ∼10-percent high. These results are interpreted as evidence for stimulated emission from "hot bands" by these laser lines. Other transitions in these two bands should also exhibit gain coefficients that have been enhanced to a lesser degree.
TL;DR: Theoretical radiation patterns from a multilayer model of a dielectric waveguide are fitted to single mode experimental profiles of three symmetrical double-heterojunction cavities to test the adequacy of the model and study the effect of the cavity parameters on the beam pattern as mentioned in this paper.
Abstract: Theoretical radiation patterns from a multilayer model of a dielectric waveguide are fitted to single mode experimental profiles of three symmetrical double-heterojunction cavities to test the adequacy of the model and study the effect of the dielectric parameters on the beam pattern. The radiation from the normal TE modes is approximated by plane waves, while for the TM modes it is given by boundary value solutions of the Maxwell equations. The adequacy of the theory is shown by the faithfulness of the fit out to large beam angles and low intensities, and the agreement of the adjusted cavity parameters to the experimental values. Small changes in either the cavity thickness or the dielectric constant of the internal n-type region have similar first order effects on the angular position of the minima in the profile as well as in the amplitude of the sidelobes. Depths of the minima decrease with departures of the structure from planarity. Pattern distortion from mode coupling at the interfaces and facets is not observed.
TL;DR: The nonlinear optical coefficient d 36 of CdGa 2 S 4 was measured to be 5 times larger than d 31 (LiNbO 3 ), which is in good agreement with theory as discussed by the authors.
Abstract: The nonlinear optical coefficient d 36 of CdGa 2 S 4 was measured to be 5 times larger than d 31 (LiNbO 3 ). This large non-linearity is in good agreement with theory.
TL;DR: The first part of a collaborative survey of the linear and nonlinear optical properties of silver thiogallate, carried out by the Centre National d'Etudes des Telecommunications (Bagneux) and the Department of Electronics of the University of Southampton, is presented in this article.
Abstract: The first part of a collaborative survey of the linear and nonlinear optical properties of silver thiogallate, carried out by the Centre National d'Etudes des Telecommunications (Bagneux) and the Department of Electronics of the University of Southampton, is presented. A detailed study of second-harmonic generation (SHG) in silver thiogallate is presented. Careful experiments in the near and medium infrared lead to a new determination of the coefficient |d_{36}| . Comparison is made with previously published values. Crystal quality is discussed and the nature of the visible twinning defects elucidated.
TL;DR: In this article, a theory of the bound electron and free-carrier contribution to the third-order susceptibility is presented, and the phase-matching configurations for THG are analyzed from the irreducible components point of view.
Abstract: Experimental and theoretical studies of third-harmonic generation (THG) in the chalcopyrite semiconductor CdGeAs 2 are presented. The phase-matching configurations for THG are analyzed from the irreducible components point of view. A theory of the bound electron and free-carrier contribution to the third-order susceptibility is presented. The experimental results are given. The effective nonlinear coefficient for type-II THG is mainly due to the free-carrier contribution, and for a hole concentration of 5 \times 10^{16} /cm3it is measured to be (13 \pm 6)10^{-11} ESU. The practical applications of THG in CdGeAs 2 are discussed.
TL;DR: In this article, the composition of a sealed discharge in He-N 2 -CO 2 and He-CO 2 mixtures was studied with a quadrupole mass spectrometer.
Abstract: The composition of a sealed discharge in He-N 2 -CO 2 and He-CO 2 mixtures was studied with a quadrupole mass spectrometer. A modulated molecular beam sampling technique allowed direct measurement of the molecular, atomic, and ionic species produced in the discharge. Effective formation and destruction rates were measured for various species. In particular, the nitrogen oxides, NO and NO 2 , are formed in sufficient quantities to affect the performance of CO 2 lasers. In the He-N 2 -CO 2 mixture the dominant ion changes from CO- 2 to NO+, while in He-CO 2 , O+ 2 becomes the major ion.
TL;DR: In this article, the authors discussed optical second-harmonic generation (SHG) using phase-matching phenomena among the guided modes, including the phase matched film thickness, the phase mismatching coefficient due to the variation of film thickness and the gain reduction factor of the guiding structure.
Abstract: This paper discusses optical second-harmonic generation (SHG) using phase-matching phenomena among the guided modes. The phase-matched film thickness, the phase-mismatching coefficient due to the variation of film thickness, and the gain reduction factor of the guiding structure are generally discussed here. The scattering loss originating from the boundary of the guide structure restricts the operation of SHG and is given by a simplified formulation.
TL;DR: In this paper, the magnetic field, electron concentration, and alignment dependencies of the tuning characteristics of an InSb spin-flip laser pumped with a 5-μm CO laser are investigated.
Abstract: A study, using heterodyne techniques, of the magnetic field (1-10 kG), electron concentration (1014- 1015cm-3), and alignment dependencies of the tuning characteristics of an InSb spin-flip laser pumped with a 5-μm CO laser is reported. These characteristics vary from a nearly continuously tunable broad-band (100-MHz) output to quasi-continuous single-mode hopping and pulling with mode tuning rates varying from greater than 75 MHz/G to less than 30 MHz/G. Large variations in the tuning rate are observed within a single-mode tuning range of less than 1 GHz. The frequency and magnetic-field dependencies of the InSb index of refraction have been measured in the near-resonance regime and a simple theoretical fit to the dispersion data is carried out. A hybrid frequency and phase-lock closed-loop system to maintain the output frequency of the spin-flip laser at a variable frequency offset from the frequency of a CO local-oscillator laser has been constructed. This system results in three major improvements in the operating characteristics of the spin-flip laser: 1) the output frequency is accurately calibrated relative to the CO-laser frequency, 2) the tuning of the spin-flip laser can be controlled in a well-calibrated fashion by varying the frequency offset, and 3) the frequency jitter and stability of the spin-flip is reduced to \lsim30 kHz.
TL;DR: In this paper, the congruent melting rare-earth aluminum garnet Gd 3 Sc 2 Al 3 O 12 (GADSCAG) has been investigated and the optimum crystal growth parameters for the undoped material are a rotation rate of 20 r/min and a growth rate of 4.6 mm/hr along the \langle 111\rangle direction.
Abstract: Investigation of the congruent melting rare-earth aluminum garnet Gd 3 Sc 2 Al 3 O 12 (GADSCAG) has been made. The optimum crystal growth parameters for the undoped material are a rotation rate of 20 r/min and a growth rate of 4.6 mm/hr along the \langle111\rangle direction. For Nd3+-doped crystals the linear growth rate is 2 mm/h. The optical properties of Nd:GADSCAG which are of interest for laser operation were also determined. The stimulated emission cross section of the 1.06-μ transition in Nd3+at room temperature is (3.2 \pm 0.3) \times 10^{-19} cm2, the fluorescence lifetime is 256 \pm 8 \mu s at an Nd3+ion density of 1 atomic percent in the crystal and the integrated peak absorption cross section in the strongest pump band (0.81 μ) is 3.8 \times 10^{-19} cm2, A comparison of the CW laser performance of identical ND:YAG and Nd:GADSCAG rods is presented.
IBM1
TL;DR: In this paper, a nitrogen-laser-pumped dye laser has been made to operate in the rotationally symmetric TE01 or TM01 modes, preserving the modes as the laser wavelength is varied.
Abstract: A nitrogen-laser-pumped dye laser has been made to operate in the rotationally symmetric TE01 or TM01 modes. The modes are preserved as the laser wavelength is varied. The mode selector allows convenient switching from one mode to the other. The theory of the operation of the mode selector is described.