Showing papers on "Spontaneous emission published in 1980"
TL;DR: In this article, a new method for measuring absorption and gain spectra of lasers is presented, which is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption.
Abstract: A new method for measuring absorption and gain spectra of lasers is presented. These spectra are deduced from measurements of spontaneous emission spectra at different laser currents supplemented by measurements of the laser line energy and the differential quantum efficiency. The spontaneous emission emerged from the side of the laser after traveling through a transparent cladding layer. At each current, the bias energy eV is determined. A simple theoretical model is used to convert eV to minority carrier density. The method is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption. A new general proof of these relations is presented. The gain versus carrier density relation at the laser line energy is measured for four samples having different active layer doping or Al composition. Gain increased superlinearly with carrier density in undoped and n‐type samples and increased slightly sublinearly in a p‐type sample. The losses a...
235 citations
TL;DR: In this paper, a 5d-4f transition in Ce3+-doped LaF3 was obtained with a 286-nm wavelength, the shortest of any solid-state laser.
Abstract: Ultraviolet laser action has been obtained from a 5d–4f transition in Ce3+-doped LaF3. The 286-nm wavelength obtained is the shortest of any solid-state laser. The approximate potential tuning range is from 275 to 315 nm.
135 citations
TL;DR: The present state of theoretical and experimental research on collective spontaneous emission (superradiance) in a system of radiators (atoms, molecules, or nuclei) is reviewed in this paper.
Abstract: The present state of theoretical and experimental research on collective spontaneous emission (superradiance) in a system of radiators (atoms, molecules, or nuclei) is reviewed. The distinction between superradiance and the amplification of spontaneous emission is discussed. There is also a discussion of conditions under which the effect can be observed and of various theoretical methods for describing superradiance: the quantum single-mode and multimode models and the semiclassical approach. Theoretical papers on superradiance in systems with dimensions smaller than the wavelength of the radiation and also in extended systems are reviewed. It is shown that superradiance may occur in weakly amplifying media. A situation in which the superradiance is oscillatory is described. The possible use of superradiance to generate coherent emission in the x-ray and ? ranges is discussed. The superradiance accompanying Raman scattering of light in atomic and molecular media is studied. The theoretical results are compared with experimental observations of superradiance in the optical range. In an appendix, the nature of the phase transition in a system of radiators interacting through an electromagnetic field is discussed.
116 citations
TL;DR: In this paper, a model of contact-limited ambipolar conduction through the electrical confinement layers is shown to influence the properties of some double heterostructure injection lasers and explains several anomalies in the measured device electrical characteristics.
Abstract: Ambipolar conduction through the electrical confinement layers is shown to influence the properties of some double heterostructure injection lasers. A model of contact-limited ambipolar conduction is consistent with known material parameters of (Al,Ga)As lasers and explains several anomalies in the measured device electrical characteristics. The portion of current lost to lasing due to poor carrier confinement in the active region of injection lasers may be greater than previously expected.
44 citations
TL;DR: In this paper, the authors showed that laser diodes with high external differential quantum efficiency (ηext) and low coefficient of spontaneous emission coupled into lasing modes (β) have a significantly higher probability of developing pulsations, which is in good agreement with theoretical predictions.
Abstract: New experimental results on self‐sustained pulsations in semiconductor lasers are presented and compared with theoretical predictions. These results show that laser diodes with high external differential quantum efficiency (ηext) and low coefficient of spontaneous emission coupled into lasing modes (β) have a significantly higher probability of developing pulsations, which is in good agreement with theoretical predictions. Furthermore, these results provide strong evidence that the laser cavity contains defects which act as optically saturable absorbing centers. These may be incorporated into the active layer of the laser during crystal growth and/or subsequent fabrication.
44 citations
TL;DR: Inert gas halide emission spectra from a Tesla discharge were studied as a function of pressure and temperature in this paper, and the energy separations, T eC -T eB, were found to be −130 cm −1 (XeCl), −80 cm − 1 (XebBr), and 375 cm−1 (KrCl).
31 citations
TL;DR: In this paper, it is shown that symmetry considerations permit one to find realistic initial conditions such that the system spontaneously evolves toward a sub-radiant system, which is called subradiance.
27 citations
TL;DR: In this paper, a model of the free electron laser is proposed which is based on the classical current of the electron in the wiggler field interacting with a quantized radiation field, but the distribution of the electrons after the interaction is essentially quantum mechanical.
26 citations
TL;DR: In this paper, the spectral composition of the spontaneous radiation, superradiance, and laser radiation emitted by a pulsed copper vapor laser was investigated, and it was found that the observed spectral structure of the laser radiation and super-radiance was governed by the hyperfine and isotopic splitting of the active levels of the copper atom.
Abstract: An investigation was made of the spectral composition of the spontaneous radiation, superradiance, and laser radiation emitted by a pulsed copper vapor laser. The time resolution was about 3 nsec. It was found that the observed spectral structure of the laser radiation and superradiance was governed by the hyperfine and isotopic splitting of the active levels of the copper atom. In the absence of saturation of the active medium a narrowing of the spectral line profiles was observed during a superradiance pulse. When saturation was achieved for superradiance and lasing, the line profiles broadened to the width of the spontaneous emission line during a radiation pulse. It was found that the temperature of the gas in the copper vapor laser did not exceed 2500°K.
24 citations
TL;DR: In this paper, optical and electrical measurements were performed on argon and argon/nitrogen plasmas in the region 1-7 cm outside the cavity, as the applied microwave power, and plasma composition were varied.
TL;DR: In this article, the authors show how to write an exact cavity-mode expansion and obtain formally simple yet exact equations of motion for real laser cavities with large output coupling and/or diffraction losses, using the actual transverse eigenmodes of the cavity as a basis set.
Abstract: The author shows how to write an exact cavity‐mode expansion and obtains formally simple yet exact equations of motion for real laser cavities with large output coupling and/or diffraction losses, using the actual transverse eigenmodes of the cavity as a basis set, and including fast transient variations, externally injected signals, and spontaneous emission noise.
TL;DR: In this paper, the effectiveness of atom scattering by the field of a standing light wave with arbitrary interaction times is calculated in a quasiclassical approximation, and the influence of spontaneous emission and the non-monochromatic nature of the field on the effective potential of an atom is discussed.
TL;DR: In this paper, the interaction of a two-level atom with two monochromatic electromagnetic fields having arbitrary amplitudes and resonance frequencies is considered, and it is shown that the time averaged upper-level population can exceed 0.5 and even reach 0.7.
Abstract: The interaction of a two-level atom with two monochromatic electromagnetic fields having arbitrary amplitudes and resonance frequencies is considered. It is shown that the time averaged upper-level population can exceed 0.5 and even reach 0.7. Its dependence on the frequency difference reveals resonance satellite peaks, which are concerned with three- and five-photon combination scattering. The widths and the resonance spectrum shifts of these peaks are found. The frequency spectrum of the spontaneous emission of an atom contains fine structure under some conditions. This structure does not exist in the case of one monochromatic field. An asymmetry in the intensity distribution for the Rabi satellites due to a field non-monochromaticity is predicted.
TL;DR: An atomicThallium laser at 535 and 377.6 nm with an external resonator, excited by photodissociating thallium iodide with the emission of an ArF excimer laser, has been built and gain and stimulated emission cross section are determined.
Abstract: An atomic thallium laser at 535 and 377.6 nm with an external resonator, excited by photodissociating thallium iodide with the emission of an ArF excimer laser, has been built. Gain and stimulated emission cross section are determined.
TL;DR: In this article, the first and second harmonics of the electron plasma frequency from localized Langmuir oscillations are computed for a field-free plasma, and it is shown that when the wavelengths of the excited modes are much greater than the scale lengths of the localized perturbation, a quadrupole radiation pattern is recovered for emission at twice the electron particle frequency.
Abstract: The radiation at the first and second harmonics of the electron plasma frequency from localized Langmuir oscillations is computed for a field-free plasma. The localized perturbations are assumed to have cylindrical symmetry about the direction of propagation of the localized perturbation. It is shown that when the wavelengths of the excited modes are much greater than the scale lengths of the Langmuir perturbation, a quadrupole radiation pattern is recovered for emission at twice the electron plasma frequency. An application to type III solar radio bursts is discussed briefly.
TL;DR: In this paper, the authors measured the radiative recombination of (100) oriented self-trapped holes and conduction electrons in CsI:Na between 1.4 and 50K.
Abstract: For pt.II see ibid., vol.13, no.6, p.993 (1980). The radiative recombination of (100) oriented self-trapped holes and conduction electrons has been measured in CsI:Na between 1.4 and 50K. At the lowest temperatures, both intrinsic emissions (290 nm and 338 nm) exhibit a partial plane polarisation perpendicular to the (100) axis of the parent VK centres. The 338 nm emission polarisation remains independent of temperature but the 290 nm emission polarisation decreases with temperature and eventually reverses its sign near 11K. Calculations show that both emissions come from a split triplet state located slightly below a singlet state which has an allowed transition to the ground state for the 290 nm emission but is forbidden for the 338 nm emission. This model explains reasonably well all the previously measured properties of self-trapped exciton emissions in CsI such as intensities, polarisations and decay times.
TL;DR: In this article, the lowest optically metastable excited state of barium, Ba(5d)3DJ, was populated by laser excitation of the 6p, 1P01←6s, 1S0 (λ=553.5 nm) transition followed by the spontaneous emission 6p 1P01→5d 3DJ (λ∼1130 nm).
Abstract: The lowest optically metastable excited state of barium, Ba(5d 3DJ), was populated by laser excitation of the 6p 1P01←6s 1S0 (λ=553.5 nm) transition followed by the spontaneous emission 6p 1P01→5d 3DJ (λ∼1130 nm). No evidence for the normally spin allowed transition 6p 1P01 →5d 1D2 (λ=1500 nm) was obtained. The deactivation of Ba (5d3DJ) by Ba (6s 1S0) is extremely efficient proceeding with a thermal cross section of 1.3±0.1 nm2 at ?730 K. This is in sensible accord with recent calculations of Ba2 potential curves.
TL;DR: In this article, a generalized relation between the main structure of d 2 J/dV 2 characteristics of point contacts with α 2 (ω)F(ω) and with spontaneous emission backflow processes is given.
TL;DR: In this paper, the authors investigated the effect of Raman scattering taking place in optical fibers, and its role in the behavior of a single-mode fiber Raman laser, where spontaneous and stimulated emissions are modified when the emitting system is placed inside a guiding structure.
Abstract: Spontaneous and stimulated emissions are modified when the emitting system is placed inside a guiding structure. This effect is investigated theoretically for Raman scattering taking place in optical fibers, and its role in the behavior of a single-mode fiber Raman laser discussed.
TL;DR: In this paper, a blue-green spontaneous emission attributed to IF from electron-beam-excited Ar/CF3I/NF3 gas mixtures was observed when mixtures of 2000-4000 Torr AR, 3 Torr CF3I and 1 Torr NF3 (or F2) were irradiated with a 3-nsec FWHM electron beam.
Abstract: The observation of intense blue-green spontaneous emission attributed to IF from electron-beam-excited Ar/CF3I/NF3 gas mixtures is reported. Intense emission from a structured band centered at a wavelength of 484 nm was observed when mixtures of 2000-4000 Torr AR (or He or Ne), 3 Torr CF3I and 1 Torr NF3 (or F2) were irradiated with a 3-nsec FWHM electron beam. Analysis of ICl and IBr spectra, which the present spectrum closely resembles, indicates that the 484-nm emission originates from the E to A 3 pi 1 transition of IF. Examination of the time dependence of metastable IF and I2 emission reveals that the IF (E) level is formed primarily by excitation transfer from metastable I(4P) states. The fluorescence efficiency of the E-A transition and the radiative lifetime of the metastable IF (E) state are estimated to be approximately 6% and 15 nsec, respectively, and it is suggested that metastable IF is an attractive candidate for a blue-green laser.
TL;DR: In this paper, the stimulated and spontaneous emission functions have been calculated for the band-to-tail and tail-totail transitions respectively in n -type photolumineseence, and p-type photioluminescence and electrolu-minescence.
PARC1
TL;DR: In this article, a high-reflection dielectric stack coating for the rear facet and apertured coatings of highly absorbing Te for the front (output) facet are used to reduce spontaneous emission from GaAs lasers.
Abstract: Spontaneous emission from GaAs lasers is substantially reduced by fabricating a high‐reflection dielectric stack coating for the rear facet and apertured coatings of highly absorbing Te for the front (output) facet. After deposition the Te is ablated by the laser mode itself and the aperture is stabilized by Al2O3 overcoating. The stimulated emission at mode center passes through the aperture unattenuated, whereas the spontaneous emission at the edges of the mode is strongly absorbed. Since spontaneous emission at mode center saturates above threshold we estimate that the ratio of stimulated to spontaneous power will approach 100 at near‐10‐mW output levels.
TL;DR: A non-hydrogenic single-electron transition model has been used to obtain partial photoionisation cross sections for values of the principal quantum number n=2,3,4,6 and 10 and the angular momentum quantum number l 0.1 keV as mentioned in this paper.
Abstract: A non-hydrogenic single-electron-transition model has been used to obtain partial photoionisation cross sections for values of the principal quantum number n=2,3,4,6 and 10 and the angular momentum quantum number l 0.1 keV), Mo32+(kT>or=1.0), and Mo35+ (KT>1.0).
TL;DR: In this paper, room temperature longwavelength (4.6μm) light emitting diodes have been fabricated from high quality lead-sulfide-selenide single crystals and spontaneous emission spectra were used to determine the temperature dependence of the band gap.
Abstract: Room‐temperature long‐wavelength (4.6‐μm) light emitting diodes have been fabricated from high quality lead‐sulfide‐selenide single crystals. Spontaneous emission spectra were used to determine the temperature dependence of the band gap. The result (3.9×10−4 eV/K) is in good agreement with data obtained by others. The bandwidth of the emission is proportional to temperature. These results suggest that thermally broadened band‐to‐band recombination is the source of electroluminescence.
TL;DR: In this paper, photoluminescence measurements performed at 6-7 K on intentionally undoped n−type liquid phase epitaxy Ga1−xAlxAs (0.19⩽x0.78) reveal transitions involving energies significantly lower than the band gap for crystals with x⩾0.47.
Abstract: Photoluminescence measurements performed at 6–7 K on intentionally undoped n‐type liquid‐phase epitaxy Ga1−xAlxAs (0.19⩽x⩽0.78) reveal transitions involving energies significantly lower than the band gap for crystals with x⩾0.47. Analysis of the luminescence data as a function of excitation intensity shows the presence of deep‐level acceptors which participate in radiative transitions, and binding energies of 0.52, 0.48, and 0.56 eV are obtained for x=0.47, 0.50, and 0.61, respectively. These values are strikingly similar to the activation energies of hole traps which are present in crystals with x=0.50, 0.61, and 0.78 and strongly suggests that the radiative acceptors and the hole traps are either identical or related states. Electron trap levels which are also present in the same crystal are found to be nonradiative.
TL;DR: In this paper, the transition probabilities and oscillator strengths for the Δv=1, 2, 3 and 4 vibration-rotation bands are derived from published theoretical dipole moment functions, obtained by an accurate multi-configuration self-consistent field procedure, in the 1∑ ground state of NO+ ion.
Abstract: Frequencies are computed for transitions in the NO+ ion which are expected to occur in the millimeter and infrared regions usually covered by millimeter-wave and infrared astronomy. The emission cross-sections and spontaneous emission rates of the microwave transitions of NO+ ion are presented. The NO+ molecule is likely to be detectable in low-temperature sources whose state temperatures are not greater than 15 K. Transition probabilities and oscillator strengths for the Δv=1, 2, 3 and 4 vibration-rotation bands are derived from published theoretical dipole moment functions, obtained by an accurate multi-configuration self-consistent field procedure, in the1∑ ground state of NO+ ion. On the basis of binary gas phase reactions, the formation and destruction of NO+ in interstellar space are also discussed.
TL;DR: In this article, the saturation behavior of the spontaneous emission intensity from a diffused-stripe InGaAsP/InP laser was studied and it was confirmed that, above the threshold current, the spectrum in the lasing region saturated over the entire spectral region.
Abstract: The saturation behavior of the spontaneous emission intensity from a diffused-stripe InGaAsP/InP laser is studied. In InGaAsP/ InP DH lasers, a spontaneous emission can be observed through the InP substrate without any optical loss. The spatial distribution and the spectrum of the emission were directly observed from the substrate surface. The spatial hole burning was observed in the wider stripe lasers but in the case of narrow stripe lasers, the spontaneous emission almost uniformly saturates. The spectrum of the emission from the center of the narrow stripe lasers was analyzed and it was confirmed that, above the threshold current, the spectra in the lasing region saturated over the entire spectral region.
TL;DR: The first known observation of spontaneous dipole-quadrupole radiative emission during the collision of an excited Ba atom with an excited Ti atom was reported in this article, where the emission occurred at the sum energy of the excited atoms.
Abstract: The first known observation of spontaneous dipole-quadrupole radiative emission during the collision of an excited Ba atom with an excited Ti atom is reported. The emission occurs at the sum energy of the excited atoms and is the dipole-quadrupole analog of the dipole-dipole emission process recently reported. A collision cross section for spontaneous radiative de-excitation of 1.5 X 10(-22) cm2 is measured.