Showing papers on "Spontaneous emission published in 1986"
TL;DR: A good approximation to the ideal localized one-photon state can be achieved by use of the photoelectric detection of the signal photon as a gate, confirmed by direct photon-counting measurements.
Abstract: In the process of spontaneous parametric down-conversion a signal and an idler photon are created simultaneously. By use of the photoelectric detection of the signal photon as a gate, a good approximation to the ideal localized one-photon state can be achieved. This has been confirmed by direct photon-counting measurements.
532 citations
Proceedings Article•
09 Jun 1986TL;DR: In this paper, the authors reexamined some of the physical effects of the vacuum and illustrated the ideas with an experiment in which spontaneous emission was effectively turned off by tuning below cutoff a waveguidelike structure that surrounded the atom.
Abstract: As Casimir pointed out many years ago, conducting surfaces and cavities alter the structure of the vacuum states, and these alterations can have physical effects. This is the underlying principle of the Casimir force and also the point of departure for a series of recent studies on atom-vacuum interactions in the microwave and millimeter wave regimes. The natural scale for such effects is set by the spontaneous emission rate. At microwave wavelengths this rate is normally too small for spontaneous emission to be observable, In Rydberg atoms, however, the rate is enhanced by a factor n4 (n is the principal quantum number, typically 20-40). Advances in experimental techniques for Rydberg atoms have opened the way to the study of the atom-vacuum interaction at long wavelengths. The result has been a renewed interest in physical effects due to the vacuum, essentially a new area of macroscopic quantum phenomena. Recent experiments with Rydberg atoms and also with free electrons are described. I will attempt to set the stage by reexamining some of the physical effects of the vacuum and illustrating the ideas with an experiment in which spontaneous emission was effectively turned off by tuning below cutoff a waveguidelike structure that surrounded the atom.1 (Invited paper, 25 min)
426 citations
TL;DR: In this paper, a theory of spontaneous emission noise is presented based on classical electromagnetic theory for open resonators, where a local Langevin force is added to the wave equation to account for spontaneous emission.
Abstract: A theory of spontaneous emission noise is presented based on classical electromagnetic theory. Unlike conventional theories of laser noise, this presentation is valid for open resonators. A local Langevin force is added to the wave equation to account for spontaneous emission. A general expression is found relating the diffusion coefficient of this force to the imaginary part of the dielectric function. The fields of lasers and amplifiers are found by solving the wave equation by the Green's function method. The lasing mode is a resonant state associated with a pole in Green's function. In this way, noise in lasers and amplifiers is treated by a unified approach that is valid for either gain guiding or index guiding. The Langevin rate equations for the laser are derived. The theory is illustrated with applications to traveling wave and Fabry-Perot amplifiers and Fabry-Perot lasers. Several new results are found: optical amplifier noise increases inversely with quantum efficiency; spontaneous emission into the lasing mode is enhanced in lasers with low facet reflectivities; and the linewidth of a Fabry-Perot laser with a passive section decreases as the square of the fraction of the cavity optical length that is active.
414 citations
TL;DR: The growth and saturation of spontaneous emission and coherent radiation in a long undulator are studied by use of the 3D Maxwell-Klimontovich equation and the results apply to proposed schemes for generation of short-wavelength coherent radiation.
Abstract: The growth and saturation of spontaneous emission and coherent radiation in a long undulator are studied by use of the 3D Maxwell-Klimontovich equation. Electron correlation, transverse radiation profiles, spectral features, transverse coherence, and intensity characteristics are discussed. The results, which agree with recent microwave experiments, are applied to proposed schemes for generation of short-wavelength coherent radiation.
281 citations
TL;DR: In this paper, the authors explain the instability of continuously operating laser due to moderate feedback from distant reflectors, and predict that the instability only occurs when the laser reaches a steady state that maximizes coherent feedback and laser light intensity.
Abstract: We explain an istability occurring in continuously operating lasers due to moderate feedback from distant reflectors. This instability occurs despite the fact that the laser is stable with respect to small deviations from steady-state operation. It is the result of finite phase and carrier number changes caused by fluctuations in spontaneous emission. We predict several properties that agree with recent experimental observations: 1) the instability only occurs when the laser reaches a steady state that maximizes coherent feedback and laser light intensity; 2) the instability vanishes at strong feedback levels; and 3) at moderate feedback levels, the laser will be nearly stable at threshold, but unstable when operated well above threshold. The latter behavior results in a nonlinear "kinked" shape in the light versus current relation.
215 citations
TL;DR: Strong competition between four-wave mixing and amplified spontaneous emission in resonant two-photon excitations is shown to generate radiation fields with strong squeezing and antibunching.
Abstract: Strong competition between four-wave mixing and amplified spontaneous emission in resonant two-photon excitations is shown to generate radiation fields with strong squeezing and antibunching. The generated fields are in a new type of coherent state which is an eigenstate of the operator corresponding to the simultaneous annihilation of photons in two modes.
195 citations
01 Sep 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a classical theory of how a signal evolves from the initial incoherent spontaneous emission in long undulators is developed based on the coupled Klimontovich-Maxwell equations.
Abstract: The following analysis develops a classical theory of how a signal evolves from the initial incoherent spontaneous emission in long undulators. The theory is based on the coupled Klimontovich-Maxwell equations. Formulas for the radiated power, spectral characteristics and electron correlations are derived. The saturation due to nonlinear effects is studied using a quasilinear extension of the theory. The results agree reasonably well with the recent Livermore experiment in the microwave range. Performance of a possible high-gain free electron laser in a short-wavelength region is evaluated.
155 citations
TL;DR: In this article, a two-terminal switching action was observed in a new optoelectronic device structure, which has a high-impedance state without light emission and a low-impingance state characterized by strong spontaneous emission, and the transition from one state to another may be induced by the appropriate optical or electrical input.
Abstract: Two‐terminal switching action is observed in a new optoelectronic device structure. The device has a high‐impedance state without light emission and a low‐impedance state characterized by strong spontaneous emission. The transition from either state to the other may be induced by the appropriate optical or electrical input. It is clear that with the appropriate optical cavity construction the switching device will operate as a laser in the on state rather than in the spontaneous mode reported here. In principle, the device offers large digital optical gain determined by its optical sensitivity and its maximum output power.
139 citations
01 Sep 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the problem of the bunched beam operation of a free electron laser was studied and the Green function corresponding to an arbitrary shape of the electron bunch, which describes the transient behavior of the system, was obtained.
Abstract: We studied the problem of the bunched beam operation of a free electron laser. Assuming the electron beam to be initially monoenergetic, the Maxwell-Vlasov equations describing the system reduce to a third order partial differential equation for the envelope of the emitted light. The Green function corresponding to an arbitrary shape of the electron bunch, which describes the transient behavior of the system, is obtained. We use Green's function to discuss the start-up problem as well as the power output and the power spectrum of self-amplified spontaneous emission.
97 citations
TL;DR: In this paper, the power spectral densities of single-mode semiconductor laser operating in a regime of injection locking are derived by appropriately taking into account the spontaneous emission processes into the lasing modes of both the master and slave lasers.
Abstract: Analytical expressions for the power spectral densities of intensity and frequency noise of single-mode semiconductor lasers operating in a regime of injection locking are derived by appropriately taking into account the spontaneous emission processes into the lasing modes of both the master and slave lasers. They show how the noise spectra of the slave are influenced by the value of the injected power, by the difference between the emission frequencies of the master and slave optical cavities, and how they are correlated to the noise properties of both the master and the free-running slave. In particular, the very low frequency part of the frequency noise of the slave turns out to coincide with that of the master within a certain frequency region whose range increases as the values of the injected signal does, too. We also present measurements of the power spectral densities obtained by means of an experimental apparatus similar to that described in [1] and show how the experimental results are accounted for by the present theory.
90 citations
TL;DR: In this paper, the authors studied the time-resolved and excitation-dependent photoluminescence of GaAs/Al x Ga 1-x As quantum well structures and showed that recombination takes place between free carriers, not excitons, at room temperature for carrier densities at and above the mid -1016cm-3level.
Abstract: Time-resolved and excitation-dependent photoluminescence of GaAs/Al x Ga 1-x As quantum well structures reveal that recombination takes place between free carriers, not excitons, at room temperature for carrier densities at and above the mid -1016cm-3level. Other samples show trapping and release of carriers from traps, evidence of dynamic Shockley, Hall, and Read recombination for optically active traps. The traps can be saturated to a large extent. Further studies show that they are associated with interfaces between different materials and that they become active at a temperature around 150 K. Results from all samples indicate that the bimolecular radiative recombination coefficient B for quantum wells is no larger than the value of B for bulk GaAs, and may in fact be smaller. This is one of the first studies of time-resolved luminescence of impurities in quantum well structures. Impurity decays at low temperatures are found to be quite slow. A spectral line which appeared to be longitudinal optical phonon-shifted emission is shown to be due to an acceptor impurity.
TL;DR: In this paper, the authors presented numerical simulations tracing the pulse evolution in the case of mode locking by synchronous pumping and showed that the perturbations introduced by the stochastic background can be severe, and that these can apparently be minimized only at the expense of the overall quality of the mode-locked pulse envelopes.
Abstract: Numerical simulations tracing the pulse evolution in the case of mode locking by synchronous pumping are presented. It is argued that strictly steady-state pulses are impossible in principle because the wings of the pulses are embedded in background radiation generated by spontaneous emission. The simulations demonstrate that the perturbations introduced by the stochastic background can be severe, and that these can apparently be minimized only at the expense of the overall quality of the mode-locked pulse envelopes.
Proceedings Article•
09 Jun 1986TL;DR: In this article, the effect of spontaneous background noise in the dynamics of mode locking by synchronous pumping is investigated and it is shown that this can cause macroscopic perturbations in the mode-locked pulses under nominally steady-state conditions.
Abstract: Numerical simulations showing the effect of spontaneous background noise in the dynamics of mode locking by synchronous pumping are presented. We demonstrate that this can cause macroscopic perturbations in the mode-locked pulses under nominally steady-state conditions1 and that the cavity length for which this effect is minimized is shorter than that required for generation of single short pulses.
TL;DR: In the limit of high gain, it is shown that the growth rate becomes less susceptible to degradation from the electron-beam quality, and the gain spectrum is related to the spontaneous emission line shape through successively higher derivatives.
Abstract: The free-electron laser can be described by solving the Lorentz-Maxwell equations self-consistently in weak optical fields. The field evolution is determined by an integral equation that allows the inclusion of an arbitrary electron distribution function in a simple way. Contour maps are used to show the gain degradation due to an electron-beam energy spread and an electron-beam angular spread. In the limit of low gain, the gain spectrum is related to the spontaneous emission line shape through successively higher derivatives. In the limit of high gain, it is shown that the growth rate becomes less susceptible to degradation from the electron-beam quality.
TL;DR: An exact solution for the collective spontaneous emission from an assembly of N identical two-level atoms, placed into a resonant damped cavity and excited to a symmetrical Dicke state with only one atom in the excited state, is derived in this article.
Abstract: An exact solution for the collective spontaneous emission from an assembly of N identical two-level atoms, placed into a resonant damped cavity and excited to a symmetrical Dicke state with only one atom in the excited state, is derived.
TL;DR: In this paper, the spectral linewidth of a GaAlAs double heterostructure laser placed in a high magnetic field was measured at 190 K. This reduction is believed to result mainly from the reduction of the enhancement factor alpha due to a quasi-one-dimensional electronic system formed by the high magnetic fields.
Abstract: The spectral linewidth of a GaAlAs double heterostructure laser placed in a high magnetic field is measured at 190 K. It is found that the power-dependent spectral linewidth is reduced by a factor of 0.6 in a magnetic field of 19 T. This reduction is believed to result mainly from the reduction of the linewidth enhancement factor alpha due to a quasi-one-dimensional electronic system formed by the high magnetic field (i.e., by quantum wire effects).
TL;DR: Amplified spontaneous emission from 3-hydroxyflavone and from a laser dye simultaneously in a binary mixture was observed in this paper, interpreted in terms of a rapid tautomerization in the ground state, minimizing reabsorption between 400 and 500 nm.
Abstract: Amplified spontaneous emission is observed from 3-hydroxyflavone and from a laser dye simultaneously in a binary mixture. This observation is interpreted in terms of a rapid tautomerization in the 3-hydroxyflavone ground state, minimizing reabsorption between 400 and 500 nm. 8 references, 4 figures, 1 table.
TL;DR: I question the claim made by Barut and Van Huele that the Lamb shift can be obtained from classical field equations without field quantization.
Abstract: I question the claim made by Barut and Van Huele (Phys Rev A 32, 3187 (1985)) that the Lamb shift can be obtained from classical field equations without field quantization
TL;DR: In this article, the authors compared the linewidth of an extended cavity semiconductor laser when it operates mode-locked and single-mode, and they found that the coherence length of the single mode is the same as that of the multiple mode, despite lower power per mode, much broader total bandwidth, and much higher spontaneous emission noise level.
Abstract: We experimentally compare the linewidth of the individual modes of an extended cavity semiconductor laser when it operates mode locked and when it operates single mode. We find that the linewidths under these two operating conditions have the same inverse dependence on the average power. Therefore, the coherence length of the mode-locked source is the same as that of the single-mode source despite lower power per mode, much broader total bandwidth, and much higher spontaneous emission noise level in the mode-locked source. It can be inferred from our data that the electric fields of over 1000 consecutive mode-locked pulses are correlated.
TL;DR: In this article, a double-peak structure of GaSb (7 nm) and Al0.25Ga0.75Sb(3 nm) multi-quantum-wells was observed at room temperature.
Abstract: Absorption peaks due to excitons in GaSb (7 nm)–Al0.25Ga0.75Sb (3 nm) multi-quantum-wells (MQW) were first observed at room temperature. The absorption spectrum exhibited a double-peak structure. The shorter wavelength and the longer wavelength peaks were assigned to be n=1 light hole and heavy hole excitons, respectively, based on a study of the polarization dependence of the guided spontaneous emission of an MQW laser diode. Measurement of asymmetric X-ray double crystal diffraction showed that negligible strain was induced in the GaSb quantum wells grown on GaSb substrate. This result implies that the hole band reversal observed by other authors using the MQW grown on a lattice-mismatched GaAs substrate rarely occurs in GaSb quantum wells grown on a GaSb substrate. The electric field effect on the exciton absorption is also presented.
TL;DR: In this paper, spontaneous emission spectra from multiple quantum well lasers grown by molecular beam epitaxy with 25-A wide GaAs wells were obtained by opening a window in the top contact stripe.
Abstract: We have recorded spontaneous emission spectra from multiple quantum well lasers grown by molecular beam epitaxy with 25‐A‐wide GaAs wells by opening a window in the top contact stripe. These spectra have a low‐energy tail and consequently the gain spectra derived from them show that laser emission occurs at a lower photon energy than the lowest energy confined particle transition. The observed laser wavelength and threshold current are consistent with the position of the peak in the gain spectrum.
TL;DR: In this article, an active gravity-wave detector based on a correlated-spontaneous-emission (CSEM) laser has potential advantages over the more usual passive scheme.
Abstract: We show that, in principle, an active gravity-wave detector based on a correlated-spontaneous-emission laser has potential advantages over the more usual passive scheme
TL;DR: In this article, an n-channel double heterostructure optoelectronic switch has been demonstrated with a high impedance state without light emission and a low impedance state with strong spontaneous emission.
Abstract: An n‐channel double heterostructure optoelectronic switch has been demonstrated As in the case of the p‐channel device, there is a high impedance state without light emission and a low impedance state with strong spontaneous emission The states are changed by optical or electrical signals and a digital optical gain of 14 is observed The switching voltage is higher and the holding current is lower than in the p‐channel case
TL;DR: In this article, the authors show that the increased loss of injected carriers due to Auger recombination process causes the increase in the hysteresis width, and that increased coupling between carriers in the gain and absorption regions, through the absorption of superradiant emission, has the effect of raising the switch-off point to higher current levels.
Abstract: An increase of hysteresis current width in bistable lasers with two or three sections was observed at higher temperatures. A rate equation analysis was performed where both carrier density dependence on lifetime and the bleaching of saturable absorption by the spontaneous emission were taken into account. We show that the increased loss of injected carriers due to Auger recombination process causes the increase in the hysteresis width. A small-signal stability analysis for the switch-off point revealed that increased coupling between carriers in the gain and absorption regions, through the absorption of superradiant emission, has the effect of raising the switch-off point to higher current levels. It was shown experimentally that, without changing the temperature, the current hysteresis width can be controlled by adjusting the current distribution in three sections.
01 Sep 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The optical klystron is a modification of an undulator which can be used to improve the gain of an FEL oscillator or to enhance the coherent spontaneous emission originating from electron bunching.
Abstract: The optical klystron is a modification of an undulator which can be used to improve the gain of an FEL oscillator or to enhance the coherent spontaneous emission originating from electron bunching. It is most useful when long enough straight sections are not available or when the energy spread is extremely small.
TL;DR: In this paper, a more complete geometrical description of amplified spontaneous emission is included in the usual numerical models for dye laser amplifiers, and a strong discrepancy with previous models is found for the low input signal regime and when evaluating the stored energy.
Abstract: A new, more complete geometrical description of amplified spontaneous emission is included in the usual numerical models for dye laser amplifiers. A strong discrepancy with previous models is found for the low input signal regime and when evaluating the stored energy. The model was thoroughly tested experimentally.