Showing papers on "Spontaneous emission published in 1985"
TL;DR: In this paper, a balanced homodyne detector was used to measure the optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms.
Abstract: Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.
1,315 citations
TL;DR: Spontaneous radiation by an atom in a Rydberg state is inhibited by use of parallel conducting planes to eliminate the vacuum modes at the transition frequency.
Abstract: Spontaneous radiation by an atom in a Rydberg state has been inhibited by use of parallel conducting planes to eliminate the vacuum modes at the transition frequency. Spontaneous emission is observed to "turn off" abruptly at the cutoff frequency of the waveguidelike structure and the natural lifetime is measured to increase by a factor of at least 20.
502 citations
TL;DR: In this article, the authors derived the gain/current curves for a single quantum well and the optimum well number, cavity length, threshold current, and current density of multi-quantum-well (MQW) lasers.
Abstract: Gain/current curves for a single quantum well are calculated. The optimum well number, cavity length, threshold current, and current density of multi-quantum-well (MQW) lasers are derived in terms of this gain curve. The limiting performance of MQW lasers is found to be better than that of graded refractive index (GRIN) lasers, assuming comparable efficiencies and spontaneous emission linewidths. The optimum threshold current for an MQW laser with a 7 μm cavity and 90 percent facet reflectivity is \sim50 \mu A/μm.
253 citations
TL;DR: This work has made the first observation of inhibited spontaneous emission of the cyclotron motion of a single electron within microwave cavity (formed by the electrodes of a Penning trap) rather than in free space.
Abstract: The radiative decay of the cyclotron motion of a single electron is significantly inhibited when the electron is located within microwave cavity (formed by the electrodes of a Penning trap) rather than in free space. This is the first observation of such inhibited spontaneous emission and the first use of a promising new system for radiative physics. Implications for precision measurements are mentioned.
218 citations
TL;DR: In this paper, a doubly resonant laser cavity driven by such atomic configurations can have vanishing diffusion coefficient for the relative phase angle for the Hanle effect in quantum beat and Hanleeffect experiments.
Abstract: In quantum-beat and Hanle-effect experiments, spontaneous-emission events from two coherently excited states are strongly correlated. A doubly resonant laser cavity driven by such atomic configurations can have vanishing diffusion coefficient for the relative phase angle.
192 citations
DOI•
01 Feb 1985TL;DR: In this article, a new analytical model for semiconductor laser amplifiers is presented, which has the virtue of avoiding excessive numerical computation and yet retaining sufficient accuracy for most cases of interest.
Abstract: A new analytical model for semiconductor laser amplifiers is presented. It has the virtue of avoiding excessive numerical computation and yet retaining sufficient accuracy for most cases of interest. The essentially new feature is the use of an appropriate mean photon density obtained by averaging the axial field distribution along the cavity length. Calculated results are presented for gain, saturation power and tuning characteristics, and their sensitivity to current density, facet reflectivities, and the spontaneous emission coefficient is explored.
170 citations
TL;DR: In this paper, the S1→S0 transition of acetylene has been studied by spontaneous and stimulated emission and two new vibrational constants, y224 and y244, were determined.
Abstract: The S1 → S0 transition of acetylene has been studied by spontaneous and stimulated emission. In the spontaneous emission studies, we report new data on low‐resolution dispersed fluorescence from an unrelaxed single rotational level of S1. Transitions into S0 levels from the zero‐point level up to ∼28 000 cm−1 of vibrational energy are reported. Earlier investigations of the emission from relaxed acetylene in a neon matrix and of partially relaxed fluorescence from a radio frequency discharge in acetylene have been reexamined and reinterpreted in the light of the present work. The stimulated emission study employed stimulated emission pumping (SEP) for high‐resolution investigations of two regions of S0 energies, one near 9550 cm−1 and another near 27 900 cm−1. Definite vibrational assignments were possible for most of the features observed in the lower energy region. This allowed the determination of two new vibrational constants, y224 and y244. The region near 27 900 cm−1 reveals a hitherto unobserved ki...
160 citations
TL;DR: Time-resolved photoluminescence measurements at room temperature of the n=1 heavy hole transition in a GaAs/AlxGa1−xAs multiple quantum well structure reveal a single-exponential decay with τ≊1 ns over a wide range of excitation densities.
Abstract: Time‐resolved photoluminescence measurements at room temperature of the n=1 heavy hole transition in a GaAs/AlxGa1−xAs multiple quantum well structure reveal a single‐exponential decay with τ≊1 ns over a wide range of excitation densities. Time‐integrated photoluminescence increases as the square of excitation energy density. These data indicate that the observed decay rate is due to nonradiative recombination. Free carriers, not excitons, govern radiative recombination in this sample.
123 citations
TL;DR: The first sub-Poisson UV light source with a Fano factor between two and three standard deviations below that for Poisson light was reported in this paper, which is the first stationary sub-poisson light source that is only weakly so.
Abstract: We report the generation of ultraviolet (253.7-nm) sub-Poisson light from Hg vapor excited by inelastic collisions with a space-charge-limited (quiet) electron beam. This first stationary sub-Poisson light source is only weakly so, with a Fano factor that is between two and three standard deviations below that for Poisson light. This is principally because of optical losses in the experimental apparatus. There does not appear to be any fundamental limit that impedes the techniques from being used to produce an intense cw light source that is also arbitrarily sub-Poisson.
106 citations
99 citations
TL;DR: The theory of radiative processes in quantum theory is formulated on the basis of self-energy, in analogy to classical radiation theory, and explicitly carried out for the calculation of the Lamb shift and spontaneous emission.
Abstract: The theory of radiative processes in quantum theory is formulated on the basis of self-energy, in analogy to classical radiation theory, and is explicitly carried out for the calculation of the Lamb shift and spontaneous emission.
ENEA1
TL;DR: The theory of free-electron lasers is extended to include the new coupling between an electron beam and optical wave propagating at an angle theta in an arbitrary harmonic, which allows the laser to be tuned to a wider range of wavelengths and to including the effects of emittance in the electron beam.
Abstract: The theory of free-electron lasers is extended to include the new coupling between an electron beam and optical wave propagating at an angle theta in an arbitrary harmonic. The coupling allows the laser to be tuned to a wider range of wavelengths and to include the effects of emittance in the electron beam. The formulation of the results in terms of coupling constants means that the existing knowledge of high gain, low gain, weak optical fields, strong optical fields, and short pulses in free-electron lasers can be immediately generalized to off-axis propagation in an arbitrary harmonic.
TL;DR: In this article, the spectral dependence of material gain and spontaneous emission in semiconductor laser amplifiers has been analyzed and it has been shown that for reflectivities below about 1 percent, increased spontaneous emission imposes more stringent limits on current density than realized hitherto.
Abstract: We present results of a new model of semiconductor laser amplifiers which differs from previous analyses in that it includes the spectral dependence of material gain and spontaneous emission. The implications of low facet reflectivities are explored in some detail. For reflectivities below about 1 percent, the increased spontaneous emission imposes more stringent limits on current density than realized hitherto. If thermal runaway is to be avoided and gains in the range of 20-30 dB are to be achieved without excessive currents, then facet reflectivities on the order of 0.1-1 percent are probably optimal. Another consequence of including the spectral dependence is that wavelengths longer than that corresponding to the unsaturated gain peak are predicted to experience enhanced amplification at high input powers by comparison to shorter wavelengths.
TL;DR: In this article, the spontaneous emission inside an injection-locked semiconductor laser does not alter the lasing field and the linewidth is only governed by the injected-field phase noise and may no longer follow the Schawlow Townes dependence on emitted optical power.
Abstract: We show that the spontaneous emission inside an injection-locked semiconductor laser does not alter the lasing field. For injection at the free-running frequency, the linewidth is only governed by the injected-field phase noise and may no longer follow the Schawlow-Townes dependence on emitted optical power.
TL;DR: In this paper, the authors investigated the role of the spontaneous emission factor in the treatment of thermodynamic equilibrium in an attenuating medium and showed that the excess spontaneous emission excitation at thermal equilibrium is cancelled by the excitations in the other modes which are correlated with that in the fundamental mode.
Abstract: Petennann [1] computed an "excess spontaneous emission factor" for gain-guided laser. In this paper, we investigate further the role of this factor. Such a factor also appears in the treatment of thermodynamic equilibrium in an attenuating medium-a seeming paradox. Further investigation shows that the excess spontaneous emission excitation at thermal equilibrium is cancelled by the excitations in the other modes which are correlated with that in the fundamental mode. In a medium with gain, cancellation also occurs in a short amplifier in which there is no gain discrimination among modes. The "excess spontaneous emission factor" is fully present only in a system in which the different higher order modes have an appreciably smaller gain than the lowest order mode, a high gain amplifier. An analysis of the signal-to-noise ratio of a high gain amplifier reveals that the excess noise factor can be fully compensated by proper input excitation by a lens arrangement. The lens arrangement provides the signal with an "excess gain" factor. An "excess gain" factor is also present when a thermal source is used.
TL;DR: In this article, a method of detecting optical waveguide modes of semiconductor epitaxial layers is presented, where the modes are excited by photoluminescence and coupled out of the semiconductor wafer by a grating etched on the surface of the guiding layer.
Abstract: A new method of detecting optical waveguide modes of semiconductor epitaxial layers is presented. The modes are excited by photoluminescence and coupled out of the semiconductor wafer by a grating etched on the surface of the guiding layer. As a consequence of this coupling, the spectrum of optical emission from the sample at fixed angles has "mode lines" superimposed on the spontaneous emission spectrum. This method is used to measure the refractive indexes of eight InGaAsP layers of different compositions. These data together with published data for the refractive index of InP were fit with a two-oscillator model to yield an algebraic description of the refractive index of the InGaAsP/InP system. The method was also used to measure the change in mode index of a laser in going from low current up to threshold. The observed change was measured to be -0.023 ± 0.006.
TL;DR: This work measured the distribution of times for single-mode laser radiation to grow from an equilibrium spontaneous-emission background to a prescribed value of the intensity and demonstrates a new technique for the description of statistical fluctuations in lasers.
Abstract: We have measured the distribution of times for single-mode laser radiation to grow from an equilibrium spontaneous-emission background to a prescribed value of the intensity. These passage-time distributions are compared with the results of Monte Carlo simulations and demonstrate a new technique for the description of statistical fluctuations in lasers.
TL;DR: The four-wave mixing process can suppress amplified spontaneous emission by preventing the excitation of the $3d$ level due to an interference between two different pathways connecting the ground ($3s$) and $3p$ states.
Abstract: Two-photon-resonant excitation of the sodium $3d$ level can lead to the generation of new frequencies either by amplified spontaneous emission at the $3d\ensuremath{\rightarrow}3p$ transition frequency or by a resonantly enhanced four-wave mixing process. Competition between these two processes has been observed. The four-wave mixing process can suppress amplified spontaneous emission by preventing the excitation of the $3d$ level due to an interference between two different pathways connecting the ground ($3s$) and $3d$ states.
TL;DR: In this paper, an excellent quantitative description of the temperature dependence of the laser threshold current density and of the relevant T o value of GaInAsP/InP 1.3 μm lasers has been reached by independent measurements of the recombination coefficients and free carrier absorption losses.
Abstract: An excellent quantitative description of the temperature dependence of the laser threshold current density and of the relevant T o value of GaInAsP/InP 1.3 μm lasers has been reached by independent measurements of the recombination coefficients and free carrier absorption losses. The recombination coefficients for the radiative band-to-band transition, nonradiative Auger recombination, and extrinsic recombination were determined experimentally, together with the free carrier absorption, especially the contribution of intervalence band absorption. The quantitative evaluation shows that nonradiative Auger carrier losses play the dominant role in the T o values around room temperature, followed by a smaller contribution due to the intervalence band absorption. Furthermore, combined pressure experiments of laser threshold current and quantum efficiency permit a detailed study of the various loss contributions and demonstrate the influence of the split-off valence band.
TL;DR: In this article, the authors studied the growth from amplified spontaneous emission of stimulated Raman scattering in air using a 20 cm-diameter, linearly polarized, 1053-nm laser beam propagating over a 20-150-in air path.
Abstract: We studied the growth from amplified spontaneous emission of stimulated Raman scattering in air using a 20-cm-diameter, linearly polarized, 1053-nm laser beam propagating over a 20–150-in air path. For 2.5-nsec square pulses we found about 1% conversion on the S(8) and S(10) rotational Raman lines of nitrogen at an intensity–length product of 12 TW/cm, which implies a small-signal gain coefficient of 2.5 cm/TW. For 1-nsec square pulses, 1% conversion requires an intensity–length product of about 16 TW/cm. The beam quality deteriorates severely above Raman threshold.
TL;DR: In this article, the spectrum of the correlation between FM and AM noises is measured in a frequency range where the spontaneous emission noise is dominant, and then the α value is calculated from the measured correlation.
Abstract: A novel method for estimating the linewidth enhancement factor α of semiconductor lasers has been developed. In this method, the spectrum of the correlation between FM and AM noises is measured in a frequency range where the spontaneous emission noise is dominant, and then the α value is calculated from the measured correlation. The α value of channeled-substrate-planar AlGaAs lasers has been estimated to be 2.2-2.8.
TL;DR: In this article, the temporal intensity variations of each longitudinal mode of a two-mode 1.5μm InGaAsP laser were precisely measured and it was concluded that spontaneous emission acts as a trigger to this hopping.
Abstract: We precisely measured temporal intensity variations of each longitudinal mode of a two‐mode 1.5‐μm InGaAsP laser. The intensities of these modes showed clear hopping between each other. It became clear for the first time that their power spectral densities represented typical Lorentzian with a cut‐off frequency between 0.7 and 1.9 MHz. This means that mode hopping follows the stochastics of a Poisson process, i.e., it occurs completely at random in time. The results of analog computer simulation, using a detailed theoretical model, supported the experimental results. It is concluded that spontaneous emission acts as a trigger to this hopping.
TL;DR: In this article, Li-like aluminium and magnesium in recombining laser-produced plasmas are reported to have increased spontaneous emission at 105.7 and 127.9 AA.
Abstract: Amplification of spontaneous emission at 105.7 and 127.9 AA is reported for Li-like aluminium and magnesium in recombining laser-produced plasmas. Evidence of gain is deduced from the variation of radiation intensity according to the length of a line-shaped plasma. Detailed calculations of rate equations with a suitable plasma model, associated with numerical simulations of plasma hydrodynamics, predict population inversions between 3d and 5f levels, in accordance with these experiments.
TL;DR: In this paper, the authors provided the theory and experiments of atoms scattering by a standing light wave under the conditions of coherent and non-coherent interaction, diffraction and interference of atomic beams.
TL;DR: In this article, the spontaneous light emission from zero-dimensional exciton states in GaAs/GaAlAs quantum wells under a high magnetic field at 80 K was observed, and the formation of such fully quantized states is evidenced by observing the wavelength shift Δ λ of the spontaneous emission peak as well as the narrowing of the spectrum width as the magnetic field is raised up to 15 T.
Abstract: We report, for the first time, the spontaneous light emission from ‘‘zero‐dimensional exciton states’’ in GaAs/GaAlAs quantum wells under a high magnetic field at 80 K. The formation of such fully quantized states is evidenced by observing the wavelength shift Δ λ of the spontaneous emission peak as well as the narrowing of the spectrum width as the magnetic field is raised up to 15 T. The observed shift Δλ is shown to be well explained by the theory in which the high magnetic field effect on two‐dimensional hydrogenic exciton is taken into account. The formation of such a novel state is further evidenced by the strong anisotropy of the photoluminescence spectrum, which depends on the direction of the magnetic field.
TL;DR: Starting from the general QED Hamiltonian for the free-electron laser (FEL), a quantum-mechanical, many-particle theory of the FEL in the laboratory frame is presented and the variance of the photon-number distribution is shown to correspond to that of thermal, or ''chaotic,'' radiation.
Abstract: Starting from the general QED Hamiltonian for the free-electron laser (FEL), a quantum-mechanical, many-particle theory of the FEL in the laboratory frame is presented. When suitable variables are introduced, the Hamiltonian is seen to a good approximation to be formally identical to the nonrelativistic Hamiltonian in the resonant (Bambini-Renieri) frame used in other treatments. The derivation is given for a general multimode laser field, although only the simpler case of single-mode operation is discussed in detail. It is shown how the large-gain evolution equations for the field, in the small-signal regime, may be obtained from the quantum theory. Then, from fourth-order perturbation theory, the change in the first two moments of the photon-number distribution in a single pass through the FEL is computed. Large-gain and saturation terms are obtained, for arbitrary values of the quantum recoil (i.e., both the classical and quantum-mechanical regimes are included). The evolution of the photon statistics over many cavity round trips is discussed. In the small-signal regime, the variance of the photon-number distribution is shown to correspond, to a good approximation, to that of thermal, or ''chaotic,'' radiation. At saturation, a significant reduction of the fluctuations is expected, but no conclusions can be drawn frommore » the perturbation-theory approach. A numerical calculation of the buildup of the field from vacuum (through spontaneous emission) is presented. For simplicity, a uniform, circularly polarized, static wiggler is assumed in the text; however, the theory may be generalized (along lines shown) to deal with nonuniform, linearly polarized and/or traveling electromagnetic-wave wigglers.« less
TL;DR: In this paper, the authors reported new results on dynamic photon statistics of 1.5μm distributed feedback buried heterostructure lasers when driven from below threshold at 1. 5 GHz modulation.
Abstract: We report new results on dynamic photon statistics of 1.5‐μm distributed feedback buried heterostructure lasers when driven from below threshold at 1.5‐GHz modulation. In contrast to Fabry–Perot lasers, a transient turn‐on delay fluctuation in the total power of about 50 ps is observed with no evidence of modal partition. These fluctuations can be explained by the randomized nature of the spontaneous emission. Typically occurring at low frequencies, these turn‐on effects can result in system timing errors. This impairment can be eliminated by modulating entirely above threshold or minimized by modulating at frequencies below a few hundred megahertz.
TL;DR: In this article, the linewidth enhancement factor in GaAs/AlGaAs multi-quantum-well (MQW) lasers has been determined from the spontaneous emission spectra below threshold.
Abstract: The linewidth enhancement factor α in GaAs/AlGaAs multi-quantum-well (MQW) lasers has been determined from the spontaneous emission spectra below threshold. It is demonstrated that the value of α in MQW lasers is appreciably smaller than that in conventional double heterostructure (DH) lasers because of the enhanced carrier-density-derivative of the optical gain.
TL;DR: In this article, the incoherent emission from an undulating electron beam in the presence of metallic boundaries is analyzed, and it is shown that the radiation characteristics depend upon a parameter involving the energy wiggler wavelength, and the waveguide transverse dimension.
Abstract: The incoherent emission from an undulating electron beam in the presence of metallic boundaries is analyzed. A general method of solving Maxwell's equations is used to express the field of a single particle in terms of vector waveguide modes. It is shown that the radiation characteristics depend upon a parameter involving the energy wiggler wavelength, and the waveguide transverse dimension. At some values of this parameter the energy spectrum and angular distribution will differ significantly from the analogous free-space results. The amount of energy emitted into resonator modes is also analyzed in terms of a similar expansion.