Showing papers on "Spontaneous emission published in 1977"
Book•
01 Jan 1977
TL;DR: In this paper, the authors present a review of classical electrodynamics and review of quantum mechanics, including the following: 1. Introduction 2. Review of classical electromagnetism 3. review of Quantum Mechanics 4. The Spontaneous Emission of Radiation 5. Selection Rules for Electric Dipole Transitions 6. Measurement of Radiative Lifetimes of Atoms and Molecules 7. Forbidden Transitions and Metastable Atoms 8. The Width and Shape of Spectral Lines 9. The Absorption and Stimulated Emission Of Radiation 10. Rad
Abstract: 1. Introduction 2. Review of Classical Electrodynamics 3. Review of Quantum Mechanics 4. The Spontaneous Emission of Radiation 5. Selection Rules for Electric Dipole Transitions 6. Measurement of Radiative Lifetimes of Atoms and Molecules 7. Forbidden Transitions and Metastable Atoms 8. The Width and Shape of Spectral Lines 9. The Absorption and Stimulated Emission of Radiation 10. Radiative Transfer and the Formation of Spectral Lines 11. Population Inversion Mechanisms in Gas Lasers 12. Resonant Modes of Optical Cavities 13. Saturation Characteristics and the Single-Frequency Operation of Gas Lasers 14. Turnable Dye Lasers and Atomic Spectroscopy 15. The Hanle Effect and the Theory of Resonance Flourescence Experiments 16. Optical Double Resonance Experiments 17. Optical Pumping Experiments 18. The Hyperfine Structure of Atoms and its Investigation by Magnetic Resonance Methods Appendix
600 citations
TL;DR: In this article, a dressed-atom approach to resonance fluorescence in intense laser fields is presented, which includes the now well known predictions concerning two-level atoms but are not restricted to such simple cases.
Abstract: A dressed-atom approach to resonance fluorescence in intense laser fields is presented. Simple and general results are derived which include the now well known predictions concerning two-level atoms but are not restricted to such simple cases. The positions of the various components of the fluorescence and absorption spectra are given by the allowed Bohr frequencies of the total system: atom+laser mode (dressed atom). The master equation, describing spontaneous emission from the dressed atom is solved in the limit of high intensities. Simple expressions, taking into account the effect of cascades, are derived for the widths of the components.
418 citations
TL;DR: In this paper, the optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament.
Abstract: Experimental measurements of the optical-beam parameters of conventional oxide-insulated GaAs stripe-geometry lasers as a function of stripe width have shown a marked difference in the waveguide mechanism of narrow-stripe ( \simeq10 \mu m) and wide-stripe ( >20 \mu m) lasers. The optical wave of narrow-stripe lasers is guided by the previously reported gain-guiding mechanism. The optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament. This self-focused guiding has been predicted theoretically. These experimental results strongly support the hypothesis that in all cases the waveguides are formed predominantly by the naturally occurring variations in carrier concentration beneath the stripe. A new and fairly comprehensive mathematical model has been developed based on this assumption. The model predicts the carrier concentration, resultant gain, and dielectric constant profiles together with the optical-beam parameters and light/current characteristics of stripe-geometry lasers. The model is applicable over a wide range of stripe widths and device structures. The results are compared with experiment over the range of stripe widths from 10-20 \mu m and found in reasonable agreement. The effects of narrowing the stripe width below 10 μm are calculated and found to be in qualitative agreement with recently published experimental results. In particular the light-output power at which a predicted "kink" in the light/current characteristic occurs is found to increase rapidly as the stripe width reduces.
169 citations
TL;DR: In this article, experimental determination of the spontaneous emission factor of an injection laser is presented, which is in good agreement with the theoretical prediction based upon the classical wave theory, which shows that the damping oscillation can be decreased in a laser consisting of very small active region.
Abstract: In this paper, experimental determination of the spontaneous-emission factor of an injection laser is presented. For a lot of conventional AlGaAs DH stripe lasers, spontaneous-emission factors of about 10-5were obtained from the measurement of the light intensity of a lasing mode versus the injected current. These values are in good agreement with the theoretical prediction based upon the classical wave theory. Brief discussion of the magnitude of the spontaneous-emission factor is given relating to the direct modulation characteristics of a semiconductor laser, which shows that the damping oscillation can be decreased in a laser consisting of very small active region.
76 citations
TL;DR: In this paper, it was shown that the signal/noise ratio of a parametric amplifier and frequency converter operating under constant pumping conditions is equal to B expressed in units of hc2/λ5 = Bvac, i.e., to the number n of photons per mode in the converted radiation.
Abstract: A proposal is made to use the relationship between the spontaneous and stimulated multiphoton transitions in determination of the spectra] brightness B and the effective temperature of noncoherent light. It is shown that the signal/noise ratio M of a parametric amplifier and frequency converter operating under constant pumping conditions is equal to B expressed in units of hc2/λ5 = Bvac, i.e., to the number n of photons per mode in the converted radiation (this number is known as the degeneracy factor). The strong frequency and angular selectivity of the coherent frequency subtraction ensures a high resolution of the proposed "photon counter". Since the relationship M = n is independent of the rate of pumping, conversion efficiency, etc., such a counter may be considered as a new type of spectral brightness and radiation temperature standard. Another possible metrological application of the parametric amplifier noise arises from the simultaneity and close coupling of the directions of emission of the idler and signal photons. This feature may be used in a source emitting a known number of photons with known momenta and directions of emission; in particular, this approach should make it possible to determine the absolute quantum efficiency of a photomultiplier.
70 citations
TL;DR: In this article, it has been shown that the entire emission spectrum is generated simultaneously as a result of the formation and propagation of cracks in the oxide film during the deformation process.
Abstract: Using Channeltron‐type detectors and magnetic discrimination techniques, it has been shown that electrons, positive and negative ions, and photons are all emitted spontaneously while oxide‐covered metals such as Al and Ni are being deformed in a tensile mode in a vacuum of approximately 10−10 Torr in total darkness. For dense anodically grown Al2O3 films of a given thickness on high‐purity Al substrates, the emission yields of all charged particles and photons are found to exhibit identically the same strain dependence. The same applies to compact thermally grown NiO films on Ni. It is concluded from these and other observations that the entire emission spectrum is generated simultaneously as a result of the formation and propagation of cracks in the oxide film during the deformation process. The shortcomings of previously proposed models for this type of triboinduced emission are pointed out, and some alternative suggestions regarding the emission mechanism are offered.
50 citations
Journal Article•
47 citations
TL;DR: In this article, the degradation and accelerated aging characteristics of currently fabricated (Al,Ga)As lasers are described, and it is shown that the dominant degradation process in present devices is not lasing related in devices operated at power levels ≥ 5 mW/face.
Abstract: An investigation of certain of the degradation and accelerated aging characteristics of currently fabricated (Al,Ga)As lasers is described. Our observations of the properties of devices aged at 70 °C, both as light‐emitting diodes and as lasers, support two conclusions relevant to degradation: (1) The dominant degradation process in present devices is not lasing related in devices operated at power levels ⩽5 mW/face; (2) laser failure is strongly correlated with an approximately 50% reduction in the spontaneous light emission (at a given current below threshold) from these devices. These inferences are consistent with a spatially uniform mode of laser degradation not, for example, related to dark‐line defects. They also imply that an LED mode of laser testing could be effective in identifying and eliminating presently dominating degradation mechanisms, i.e., those limiting continuously operating laser lifetimes to median values of about five years at room temperature. A different degradation mechanism whi...
42 citations
TL;DR: In this paper, the dependences of the decay times τ and emission peaks hvm of the 0.94, 1.2, and 1.3 eV luminescence bands on the equilibrium electron concentration n0 in n-type GaAs are studied with the aim to arrive at the exact scheme of the electronic transitions leading to the above emission bands.
Abstract: The dependences of the decay times τ and emission peaks hvm of the 0.94, 1.0, 1.2, and 1.3 eV luminescence bands on the equilibrium electron concentration n0 in n-type GaAs are studied with the aim to arrive at the exact scheme of the electronic transitions leading to the above emission bands. Weak dependences of τ and hvm on n0 for low doping levels (at n0 ⪅ 1017 cm−3) followed by a decrease in τ and an increase in hvm for high doping levels (at n0 ⪆ 1017 cm−3) are observed. From this follows that the emission bands at hvm = 0.94, 1.0, 1.2, and 1.3 eV in n-type GaAs for doping levels below 1017 cm−3 are due to radiative recombination of localized electrons in donor-acceptor pairs and for doping levels above 1017 cm−3 are due to radiative recombination of free electrons with holes at the acceptor levels of the donor-acceptor pairs. The corresponding probabilities are found of electron transitions in the donor-acceptor pairs and the free electron capture coefficients by the pair acceptor levels. Using the scheme established of the electronic transitions a new analysis of temperature dependences of the decay times and emission intensities for the above luminescence bands is made and, as a result, more accurate data for the main recombination parameters of the 0.94, 1.0, 1.2, and 1.3 eV radiative centres are obtained.
[Russian Text Ignored]
39 citations
TL;DR: In this article, a general analysis of the characteristics of laser action resulting from plasma recombination in the afterglow of a gas discharge is made, and the requirements to be satisfied by the distribution of the active levels are formulated in the approximation of level groups bearing in mind that the transitions due to electron deexcitation are very important during the plasma relaxation period.
Abstract: A general analysis is made of the characteristics of laser action resulting from plasma recombination in the afterglow of a gas discharge. It is shown that efficient pumping of the active levels by impact-radiative recombination can be achieved by establishing a fairly high plasma density, cooling as fast and as much as possible the electron gas after a current pulse, and utilizing the recombination of doubly charged ions with a high initial concentration. It is shown that the most convenient approach is the utilization of the recombination in the afterglow of a discharge in a vapor of an easily ionizable element mixed with helium. The requirements to be satisfied by the distribution of the active levels are formulated in the approximation of level groups bearing in mind that the transitions due to electron deexcitation are very important during the plasma relaxation period. A generalized criterion is obtained for the existence of a population inversion. The cases of radiative and colh'sional regimes are discussed separately for the case of widely spaced levels. The paper concludes with a formulation of the general requirements to be satisfied by the distribution of levels so that an inversion is obtained under recombination-collisional kinetics conditions.
36 citations
TL;DR: In this paper, the Born-Oppenheimer potential energy and electric-dipole-moment surfaces were obtained from an electronic configuration-interaction calculation with near-Hartree-Fock limit orbitals expanded in a floating gaussian basis.
TL;DR: In this paper, a simple and versatile laser technique for the detection of photon echoes in molecular excited ensembles is presented, which utilizes two optical pulses followed by a third probe pulse which converts the optical polarization induced by the laser into a change in excited population that gives rise to spontaneous emission.
TL;DR: The role of dissociation recombination in the processes of excitation of XeCl ∗ has been discussed in this article, where a mixture of He:Xe:BCl 3 at pressures of 1 to 7 atm with a transverse discharge is presented.
TL;DR: In this paper, long-time deviations from the exponential decay law in atomic spontaneous emission are demonstrated to be unusually sensitive to the form of the interaction Hamiltonian used to describe the decay.
TL;DR: In this article, it was shown that the L(J) irregularities are due to variations of the stimulated-emission rate that are related to the external cavity induced instability in the time domain.
Abstract: (Ga,Al)As CW diode lasers with a linear light output L versus pumping current J characteristic have been coupled to an external optical cavity. This coupling is shown to induce nonlinearities in the L(J) characteristic. The light output of external-cavity-coupled CW diode lasers is self-pulsing at a resonance frequency of the external cavity and/or at a low frequency in the range of 3-30 MHz. It is found that irregularities in the light output-current characteristic are strictly related to changes of the type of self-pulsation. On the basis of separate measurements of the stimulated and spontaneous emission, it appears that the coupling to the external cavity affects the ratio between stimulated and spontaneous emission but not the total radiative recombination rate. It is supposed that the L(J) irregularities are due to variations of the stimulated-emission rate that are related to the external-cavity-induced instability in the time domain.
TL;DR: In this article, the fine structure of the 23P33D line of He I has been recorded by a saturated-absorption technique, and preliminary results on pressure effects are presented.
TL;DR: The photoluminescence spectra in Ge1-xSex glasses with a composition of 0.5≤x≤0.9 along with the optical absorption spectra have been measured as mentioned in this paper.
Abstract: The photoluminescence spectra in Ge1-xSex glasses with a composition of 0.5≤x≤0.9 along with the optical absorption spectra have been measured. The position of the emission peak is almost independent of the Se composition. The emission intensity, however, is most intense for the composition Ge–Se2, indicating the dominant role of GeSe2 stoichiometric structure of Ge–Se glasses on the radiative recombination. The annealing of samples causes a reduction in the energy range of the tail states and thus an increase in the optical energy gap together with an enhancement of the emission intensity. An absorption band is found in the specral range corresponding to the photoluminescence. The absorption coefficient of the absorption band has a close relation with the emission intensity. A model which is partly based on the recombination edge model is proposed. The localized states near the midgap which act as recombination centers are presumed to be due to structural defects associated with GeSe4 molecules.
TL;DR: In this paper, strong radiation induces correlations between spontaneously emitted photons of different frequencies, and the spectral distributions of these correlations are discussed in terms of the spectral distribution of the correlations among different frequencies.
TL;DR: In this article, the conditions under which large and small molecules may undergo optical dephasing are described and the relationship between coherent preparation of excited states and the intramolecular and intermolecular processes are discussed.
TL;DR: In this paper, an external-grating operation of double-heterojuncfion (DH) laser was proposed to determine the index dispersion quantity over a wide wavelength range.
Abstract: InP-In 1-x Ga x P 1-z As z -InP ( x \sim 0.08, z \sim 0.17 ) double-heterojuncfion (DH) lasers emitting at \lambda \sim 1.0 \mu m (77 K) have been fabricated by constant-temperature liquid-phase epitaxy (LPE). The crystal-growth process is described and compared to previous work on visible spectrum ( \lambda \sim 6000 -A) In 1-x Ga x P 1-z As z double-heterojunction lasers. Emission spectra are presented for the near-infrared quaternary DH lasers. In particular, the observation of cavity oscillations in the low-level spontaneous-emission spectra allows the determination of the index dispersion quantity over a wide wavelength range. Finally, these In 1-x Ga x P 1-z As z DH lasers are operated in an external-grating cavity. Such operation permits tunable, narrow-linewidth laser emission and provides information concerning radiative-recombination processes. Comparisons are made to earlier work on external-grating operation of visible-spectrum ( \lambda \sim 6000 -A) In 1-x Ga x P 1-z As z DH lasers.
TL;DR: In this paper, the authors studied spontaneous emission from a multilevel atom from the viewpoint of quantum beats and established the relation of the rate of change of the energy of the atomic system to the total power radiated in the far zone.
Abstract: Spontaneous emission from a multilevel atom is studied from the viewpoint of quantum beats. The master equation describing the atomic dynamics is shown to have some parameters that oscillate at the beat frequencies, and because of this a Pauli type of master equation for the diagonal elements of the density matrix is not obtained. As a result, the transition rates in the atomic system show the characteristic beats. The relation of the rate of change of the energy of the atomic system to the total power radiated in the far zone is also established. The normally and antinormally ordered correlation functions of the spontaneously emitted radiation are calculated under the approximation that the level widths are much smaller than the beat frequencies. The contribution arising from the interference of the free field and the source terms to antinormally ordered correlations is carefully evaluated. The nature of beats present in normally and antinormally ordered correlations is discussed, and their detection from the viewpoint of causing transitions in another atom is considered. The change in the nature of beats due to atomic collective effects is studied. Finally, it is shown that because of quantum effects, intensity correlations do not show any beats.
IBM1
TL;DR: In this article, the emission probability of hot electrons from the Si substrate into the gate SiO 2 layer has been investigated by measuring the gate current directly in case of channel electron emission, or the optically induced hot-electron emission current in the case of emission of thermally generated leakage electrons.
Abstract: Short-channel effects and the theory of scaling require proportionally increased doping concentrations in the surface channel and/or the bulk substrate regions of Si IGFET's of short channel lengths. Unless the applied voltages are reduced accordingly, appreciable emission of hot electrons from the Si substrate into the gate SiO 2 layer may occur. The emission processes can be studied by measuring the gate current directly in the case of channel electron emission, or the optically induced hot-electron emission current in the case of emission of thermally generated leakage electrons. Absolute emission probabilities as well as relative emission characteristics can be determined. These emission characteristics are useful not only for designing Si devices but also for quantitative testing of theoretical models of the emission process. Important physical mechanisms and device parameters in the emission process are discussed.
TL;DR: In this paper, the spatial variation of the junction voltage and current distribution is deduced from measured profiles of the intensity of high-frequency light across the emitting facet of stripe lasers, and a new theory is developed of the current spreading in a layered structure which successfully describes the features of the measured distributions.
Abstract: The spatial variation of the junction voltage and current distribution are deduced from measured profiles of the intensity of high‐frequency light across the emitting facet of stripe lasers. The dependence of voltage on current follows closely the current dependence deduced from study of the external beam. Below, threshold, the shape of the voltage profile is found to be practically independent of current. The change at threshold in the differential conductance of the junction has only a minor effect on the profile, although its effect is observable over the entire front of the coherent waves. However, there is no apparent modification of the profile connected with the structure of the coherent illumination of the facet. A new theory is developed of the current spreading in a layered structure which successfully describes the features of the measured distributions. Using only material parameters of the layers of the laser, it predicts to good approximation the observed current spreading. The modifications...
TL;DR: In this article, the statistical and spatial distribution of a source of pulsed A.S.E. working in the linear regime were found to agree with those of spontaneous emission in a time short compared with a transition lifetime, as predicted by Allen et al.
15 Dec 1977
TL;DR: In this paper, a semiclassical approach was used to study the emission in molecular systems in an intense laser field, with a view towards cooperative chemical and optical pumping in laser production.
Abstract: Collion-induced emission in molecular systems in an intense laser field is studied using the semiclassical approach, with a view towards cooperative chemical and optical pumping in laser production. The formalism is developed with the electronic-field representation, which treats collision and radiative interaction on the same footing. Electronic-field surfaces can be regarded as forming spectra for spontaneous emission; and particular emission events can be accounted for by propagating classical trajectories on emission electronic-field surfaces. Pre-emission loss from the excited state is dealt with by propagating classical trajectories on a loss surface along a complex contour of emission branch points. This loss surface is derived on the basis of localized radiative couplings between electronic-field states and provides a framework to treat the general problem of discrete state-continuum interactions. The formalism is applied to a two-state, collinear exponential model to compute S -matrix elements and transition probabilities between asymptotic states.
TL;DR: In this article, the problem of reconciling the Bose-Einstein statistics of the incident radiation field with the Fermi-Dirac statistics of electron population in a photoconductor which is in equilibrium with the radiation field is considered.
Abstract: In this article we consider the problem of how to reconcile the Bose-Einstein statistics of the incident radiation field with the Fermi-Dirac statistics of the electron population in a photoconductor which is in equilibrium with the radiation field. A Langevin approach is followed, based on Einstein's rate equations. Results for the noise sources associated with absorption, stimulated emission, and spontaneous emission, are derived. These results are shown to be consistent with the Fermi-Dirac statistics of the electron processes; also, the various sources are shown to reconstitute the black-body radiation field.
TL;DR: In this article, it was shown that the small incompleteness of the saturation agrees with the value predicted by the new nonlinear theory of injection lasers, and the junction voltage, spontaneous emission, and mode powering of this cw laser are interconnected by the theory just as they were in the various types of pulsed lasers already described.
Abstract: Recently published data concerning a contemporary well‐behaved cw stripe‐geometry injection laser was accompanied by the assertion that above threshold both the junction voltage and the spontaneous emission exhibit ’’complete saturation’’. This paper shows by detailed analysis of the data that in fact the small incompleteness of the saturation agrees with the value predicted by the new nonlinear theory of injection lasers. The junction voltage, spontaneous emission, and mode powering of this cw laser are interconnected by the theory just as they were in the various types of pulsed lasers already described.
TL;DR: In this paper, the dynamic characteristics of semiconductor lasers are calculated with singlemode rate equations, taking into account spontaneous emission factor β and bias current, with single mode rate equations.
Abstract: Dynamic characteristics of semiconductor lasers are calculated with single-mode rate equations, taking into account spontaneous emission factor β and bias current