Showing papers on "Spontaneous emission published in 1989"
TL;DR: A single lasing mode driven by a three-level ''quantum-beat'' atomic configuration can show gain without population inversion or optical absorption into an excited state without spontaneous or stimulated emission.
Abstract: A single lasing mode driven by a three-level ``quantum-beat'' atomic configuration can show gain without population inversion or optical absorption into an excited state without spontaneous or stimulated emission.
690 citations
TL;DR: Amplified spontaneous emission and stimulated emission spectra of the GaAs/AlGaAs quantum wires exhibit fine structure arising from transitions between lateral, one-dimensional electron and hole subbands.
Abstract: We report the first observation of stimulated emission in quasi-one-dimensional semiconductor quantum wires Amplified spontaneous emission and stimulated emission spectra of the GaAs/AlGaAs quantum wires exhibit fine structure arising from transitions between lateral, one-dimensional electron and hole subbands The observed subband separations, \ensuremath{\sim}10 meV, are consistent with the calculated ones
513 citations
TL;DR: In this paper, it was shown that spontaneous emission is not a property of an isolated atom but of an atom-vacuum system and can be inhibited or enhanced by placing the excited atom between mirrors or in a cavity.
Abstract: Ever since Einstein demonstrated that spontaneous emission must occur if matter and radiation are to achieve thermal equilibrium, physicists have generally believed that excited atoms inevitably radiate. Spontaneous emission is so fundamental that it is usually regarded as an inherent property of matter. This view, however, overlooks the fact that spontaneous emission is not a property of an isolated atom but of an atom‐vacuum system. The most distinctive feature of such emission, irreversibility, comes about because an infinity of vacuum states is available to the radiated photon. If these states are modified—for instance, by placing the excited atom between mirrors or in a cavity—spontaneous emission can be greatly inhibited or enhanced.
500 citations
TL;DR: In this article, a simple rate equation formula is derived for a four-level laser assuming enhanced spontaneous emission into the cavity, and it is shown that the spontaneous emission rate alteration caused by the cavity plays an essentially important role for these characteristics.
Abstract: We describe the light output properties of single mode lasers having cavity dimensions on the order of the emitted wavelength. A simple rate equation formula is derived for a four‐level laser assuming enhanced spontaneous emission into the cavity. These rate equation analyses show that increasing the coupling of spontaneous emission into the cavity mode causes the lasing properties to become quite different from those of usual lasers having cavity dimensions much larger than a wavelength. We find that the lasing threshold disappears, the light emission efficiency increases, relaxation oscillations do not occur, and the dynamic response speed is improved. It is shown that the spontaneous emission rate alteration caused by the cavity plays an essentially important role for these characteristics.
331 citations
TL;DR: In this paper, the authors studied the spontaneous emission (ASE) in erbium-doped single-mode fiber amplifiers operating at lambda = 1.53 mu m. The ASE noise spectra obtained from the theory were found to be in excellent quantitative agreement with the experimental data.
Abstract: Amplification of spontaneous emission (ASE) in erbium-doped single-mode fiber amplifiers operating at lambda =1.53 mu m is studied theoretically and experimentally. The ASE noise spectra obtained from the theory are found to be in excellent quantitative agreement with the experimental data. The observed changes in ASE spectral shapes under different population inversion conditions are also explained. The model may be used to evaluate the performance of erbium-doped fiber lasers as well as to assess the noise characteristics of erbium-doped fiber amplifiers as applied to wavelength-division multiplexing optical communications. >
305 citations
TL;DR: It is shown that an excess spontaneous emission of this type, and also a correlation between the spontaneous emission into different cavity modes, will in fact be present in all open-sided laser resonators or optical lens guides.
Abstract: Petermann first predicted in 1979 the existence of an excess-spontaneous-emission factor in gain-guided semiconductor lasers. We show that an excess spontaneous emission of this type, and also a correlation between the spontaneous emission into different cavity modes, will in fact be present in all open-sided laser resonators or optical lens guides. These properties arise from the non-self-adjoint or non-power-orthogonal nature of the optical resonator modes. The spontaneous-emission rate is only slightly enhanced in stable-resonator or index-guided structures, but can become very much larger than normal in gain-guided or geometrically unstable structures. Optical resonators or lens guides that have an excess noise emission necessarily also exhibit an ``excess initial-mode excitation factor'' for externally injected signals. As a result, the excess spontaneous emission can be balanced out and the usual quantum-noise limit recovered in laser amplifiers and in injection-seeded laser oscillators, but not in free-running laser oscillators.
182 citations
TL;DR: In this paper, the authors considered carrier-carrier and carrier-longitudinal-optical (LO) phonon scattering mechanisms, and showed that hole-hole, electron-hole and hole-LO phonon scaling are dominant in spectral broadening.
Abstract: Intraband relaxation time, which causes spectral broadening of optical gain and spontaneous emission spectra, is estimated theoretically for quantum-well lasers. Carrier-carrier and carrier-longitudinal-optical (LO) phonon scattering mechanisms are considered, and it is shown that hole-hole, electron-hole, and hole-LO phonon scattering are dominant in spectral broadening. Intraband relaxation time determined by all of these mechanisms increases slightly with the decrease of well width. The dependence of intraband relaxation time on temperature, carrier density, and energy of electron and hole is also shown. Spectral line shape is discussed as an extension of the above calculation, and an approximated formula is given. >
149 citations
TL;DR: In this article, a detailed nonlinear model of the performance of single-frequency laser structures operating both below and above threshold is discussed, taking longitudinal-mode spatial hole burning into account.
Abstract: A detailed nonlinear model of the performance of single-frequency laser structures operating both below and above threshold is discussed. Arbitrary series combinations of uniform pitch grating, linearly-chirped pitch grating and plane guide sections can be analyzed-taking longitudinal-mode spatial hole burning into account. The material properties of each section of a device structure can be specified. The output power from each end of the laser and the emission wavelength, and the longitudinal intensity, carrier density, and relative permittivity profiles are predicted as a function of drive current above threshold for each lasing mode. The linewidth is also estimated while allowing for the nonuniform longitudinal distribution of spontaneous emission into the mode in a physical manner. The model was used to provide the data with which to trade off the numerous interacting performance parameters of a lambda /4 phase-shifted DFB (distributed-feedback) laser. The design options are then summarized. >
145 citations
TL;DR: Measurements are presented which show that, in contrast with Ref. 9, the collisional loss rate has a marked dependence on the trap laser intensity, and strong circumstantial evidence is presented that the dependence at very low intensities is due to hyperfinechanging collisions between ground-state atoms.
Abstract: We have studied the collisional loss rates for very cold cesium atoms held in a spontaneous-force optical trap. In contrast with previous work, we find that collisions involving excitation by the trapping light fields are the dominant loss mechanism. We also find that hyperfine-changing collisions between atoms in the ground state can be significant under some circumstances. PACS numbers: 32.80.Pj, 34.50.Rk Spontaneous-force light traps' have provided a way to obtain relatively deep static traps for neutral atoms. These allow one to produce samples containing large numbers of very cold atoms. In this paper we present an experimental study of the collisions which eject atoms from such a trap. These collisions are of considerable interest because the temperatures of the trapped atoms (10 K) are far lower than in usual atomic collision experiments. The theory of such low-energy collisions and their novel features have been discussed by several authors. Perhaps the most notable feature is that the collision times are very long, and the collision dynamics are dominated by long-range interactions and spontaneous emission. These collisions also have important implications with regard to potential uses of optically trapped atoms. For many applications the maximum density that can be obtained is a critical parameter, and these collisions limit the attainable density. There have been two experimental studies of collisions in optical traps. Gould et al. measured the cross section for associative ionization of sodium. However, there is no evidence that this process is significant in limiting trapped-atom densities, and for some atoms, including cesium, it is energetically forbidden. Prentiss et al. studied the collisional losses which limited the density of sodium atoms which were held in a spontaneous-force trap. Their surprising and unexplained results were a direct stimulus for our work. In particular, they observed no dependence of the loss rate on the intensity of the trapping light. This was quite surprising, because a ground and an excited atom interact at long range via the strong 1/r resonant dipole interaction, and a portion of the excited-state energy can be converted into sufficient kinetic energy to allow the atoms to escape from the trap. By comparison, two atoms in their ground states interact only through a much weaker short-range 1/r Van der Waals attraction, and even when such collisions occur, they may not produce significant kinetic energy to cause trap loss. This implies that the dominant collisional loss mechanism would involve the excited atomic states, and thus depend on the intensity of the light which causes such excitations. In this paper we present measurements which show that, in contrast with Ref. 9, the collisional loss rate has a marked dependence on the trap laser intensity. We will present strong circumstantial evidence that the dependence at very low intensities is due to hyperfinechanging collisions between ground-state atoms. We believe that the loss rates at higher intensities are associated with collisions involving excited states, and are the type discussed by Gallagher and Pritchard. As discussed in Ref. 7, these collisions are very different from normal ground-excited-state atomic collisions in which two initially distant atoms, A and A approach, collide, and separate in a time much less than the radiative lifetime of the excited state. In contrast, for these very-low-temperature collisions the absorption and emission of radiation in the midst of the collision drastically alter the motion. In particular, if the excitation takes place when the two atoms are far apart (R) 1000 A) they will reradiate before being pulled into the small-R region where energy transfer occurs. However, if they are sufficiently close when excited, they can be pulled close enough together for substantial potential energy to be transferred into kinetic energy before decaying. The two dominant transfer processes are excited-state fine-structure changes and radiative redistribution. In the first, A changes its fine-structure state in the collision and the pair acquire a fine-structureinterval worth of kinetic energy. The second process, radiative redistribution, refers to A Areemitting a -photon which, because of the A-A* attractive potential, has substantially less energy than that of the photon which was initially absorbed. This energy difference is transferred to the subsequent kinetic energy of the ground-state atoms. The trap loss rate depends on the probability of exciting such "close" A-A pairs, and this probability is determined by the frequency and intensity of the exciting radiation. Light which is tuned to the red of the atomic resonance frequency, vo, excites pairs which are closer together (and shifted in energy) and thus is more eN'ective at causing trap loss than light which is at vo. We tested this hypothesis by examining how the loss
145 citations
TL;DR: The Petermann excess-spontaneous-emission factor is taken into account and it is found that the quantum-noise fluctuations or Schawlow-Townes fluctuations in the output spectrum of a laser oscillator will be multiplied by this excess noise factor.
Abstract: When the Petermann excess-spontaneous-emission factor described in the accompanying paper [Siegman, preceding paper, Phys. Rev. A 39, 1253 (1989)] is taken into account, we find that the quantum-noise fluctuations or Schawlow-Townes fluctuations in the output spectrum of a laser oscillator will be multiplied by this excess noise factor. The excess spontaneous emission in a laser oscillator cannot be canceled by adjoint-mode-excitation techniques as it can be in a laser amplifier. The resulting noise enhancement can be very sizable (100 to 1000 times or more) in gain-guided laser oscillators, and especially in laser oscillators using geometrically unstable cavities with moderate to high magnifications and Fresnel numbers.
121 citations
TL;DR: In this article, a quantum theory of one-dimensional laser cooling of free atoms using a transition with a 0 ground state and a 1 excited state was presented, valid both for broad lines (recoil energy small compared with the energy width of the excited level) and for narrow lines.
Abstract: We present a quantum theory of one-dimensional laser cooling of free atoms using a transition with a J = 0 ground state and a J = 1 excited state. This treatment is valid both for broad lines (recoil energy small compared with the energy width ℏ Γ of the excited level) and for narrow lines. For broad lines we recover the well-known cooling limit for a two-level transition (∼ℏΓ/2), whereas for a narrow line the cooling limit is found to be of the order of the recoil energy. The stationary momentum distribution is obtained for both cases and is found to be close to the one obtained by Monte Carlo simulations.
TL;DR: In this paper, the interference effects that can be observed in the two output arms of a lossless beam splitter are calculated for incident light in the form of a photon-pair excitation in two input arms.
Abstract: The interference effects that can be observed in the two output arms of a lossless beam splitter are calculated for incident light in the form of a photon-pair excitation in the two input arms. The output state that occurs when the photon pair is excited in a single input arm resembles that expected for independent classical particles, whereas quantum interference effects occur when the photon pair is divided between the two input arms. Detailed output photocount correlation functions are calculated for two-photon input states produced by a two-atom light source, a degenerate or nondegenerate parametric oscillator in a high-Q cavity, and an atomic cascade emission light source.
TL;DR: The strength of the stimulated emission signal suggests that it may have applications as a diagnostic technique, and rapid depletion of the laser-excited state by the stimulating emission process may have an impact on the use of diagnostic techniques based on multiphoton excitation in oxygen and in other species.
Abstract: We report detection of stimulated emission from the atomic-oxygen 3 3P–3 3S transition at 845 nm after two-photon excitation of the 2 3P–3 3P transition using 226-nm laser radiation. We study this stimulated emission process in flames and in room-temperature flows of O2 and N2O and compare its behavior with that of fluorescence signals acquired simultaneously. Rapid depletion of the laser-excited state by the stimulated emission process may have an impact on the use of diagnostic techniques based on multiphoton excitation in oxygen and in other species. The strength of the stimulated emission signal suggests that it may have applications as a diagnostic technique.
TL;DR: The first observation of optically excited stimulated emission in atomic hydrogen is described in this paper, where the two-photon n = 1 → n = 3 transition of hydrogen atoms in low-pressure flames is excited with 205-nm radiation produced by using a beta barium borate crystal to frequency mix the fundamental and frequency-doubled radiation from a 615-nm pulsed dye laser.
Abstract: The first observation to the author’s knowledge of optically excited stimulated emission in atomic hydrogen is described. The two-photon n = 1 → n = 3 transition of hydrogen atoms in low-pressure flames is excited with 205-nm radiation produced by using a beta barium borate crystal to frequency mix the fundamental and frequency-doubled radiation from a 615-nm pulsed dye laser. The resulting 656-nm n = 3 → n = 2 Balmer-α radiation is readily observable by eye as a coherent beam propagating in both the forward and reverse directions. We describe a variety of characteristics of the stimulated emission, comparing its behavior with simultaneous measurements of two-photon-excited fluorescence, and discuss the possibility that the stimulated-emission process may affect the quantum yield of fluorescence and ionization detection methods. Potential diagnostic applications of two-photon-excited stimulated-emission detection for measuring atomic hydrogen in flames are demonstrated, using simultaneous profile measurements of stimulated emission and fluorescence signals.
TL;DR: In this paper, a program for calculating the bound → continuum transition intensities associated with photodissociation, spontaneous emission or predissociation of a diatomic molecule is described.
TL;DR: In this article, it was shown that the fluorescence emitted in front of a mirror exhibits angular and spectral localization effects that are caused by self-interference in the spontaneous emission from a Wiener-fringe pattern.
TL;DR: A model for the oxygen in ZnSe acting as an acceptor is proposed and the acceptor level and the effective charge of oxygen are estimated to be about 80 meV and -0.9, respectively, using the energy values of the luminescence peaks of bound-exciton and donor-acceptor emission.
Abstract: The optical properties of oxygen-doped ZnSe grown by molecular-beam epitaxy were studied by means of photoluminescence spectroscopy. Oxygen-related peaks were observed at about 4437 and at about 4550 A\r{}, where phonon replicas also appeared. These peaks may be caused by the radiative recombination of excitons bound to neutral oxygen atoms and donor-to-oxygen-acceptor emission, respectively. Observation of donor-acceptor emission in which the acceptor is an isoelectronic acceptor is reported for the first time. Oxygen, which is an isoelectronic impurity in ZnSe, can act as an acceptor in the same way as the generally used dopants such as nitrogen. A model for the oxygen in ZnSe acting as an acceptor is proposed. The acceptor level and the effective charge of oxygen are estimated to be about 80 meV and -0.9, respectively, using the energy values of the luminescence peaks of bound-exciton and donor-acceptor emission.
TL;DR: In this paper, a LiYF4:15% Er3+ crystal at room temperature under diode laser excitation for 2.81 μm emissions and under argon ion laser exciting for two.5 mW absorbed power at 0.795 μm (diode) is obtained for the 2.1 μm wavelength.
Abstract: cw pumped laser emission on six different wavelengths is obtained for the first time in a LiYF4:15% Er3+ crystal at room temperature under diode laser excitation for 2.66, 2.716, 2.81 μm emissions and under argon ion laser excitation for 2.77, 2.81, 2.84, 2.85 μm emissions. Threshold of 5 mW absorbed power at 0.795 μm (diode) is obtained for the 2.81 μm wavelength. Time and power evolution of the laser emissions are presented. The type of up‐conversion taking place during 2.81 μm laser emission is shown to be of the addition of photons by energy transfer (APTE) type involving a two‐photon summation which depopulates the 4I11/2 rather than the 4I13/2 state as up to now believed.
TL;DR: Spectral observations suggest that droplet lasing emission is supported by resonances of a single mode order, and exhibits faster rise times and is shorter lived than corresponding bulk-liquid fluorescence.
Abstract: Micrometer-sized droplets of Rhodamine 6G solution in water and ethanol are irradiated by high-intensity nanosecond pulses from a frequency-doubled Nd:YAG laser. Coupling of the spontaneous fluorescence emission with natural resonant modes of the spherical droplets results in stimulated emission, with each droplet behaving like a laser cavity. Spectral observations suggest that droplet lasing emission is supported by resonances of a single mode order. The emission exhibits faster rise times and is shorter lived than corresponding bulk-liquid fluorescence. Lasing in droplets is generally initiated almost simultaneously with elastic scattering, unlike stimulated Raman scattering, which is significantly delayed.
TL;DR: In this paper, the authors describe the experimental implementation and theory of a new technique for the time resolved study of intramolecular vibrational redistribution: time resolved fluorescence depletion (TRFD), which is obtained by using two pulses of identical wavelength and duration to create and then stimulate emission from a vibrational state in S1.
Abstract: This paper describes the experimental implementation and theory of a new technique for the time resolved study of intramolecular vibrational redistribution: time resolved fluorescence depletion (TRFD). Picosecond time resolution is obtained by using two pulses of identical wavelength and duration to create and then stimulate emission from a vibrational state in S1. Spontaneous emission intensity is measured as a function of delay between pulses. By monitoring the efficiency with which the second pulse stimulates emission, the evolution of the initial optically prepared state can be followed. A description of the apparatus built for these experiments is also presented.
TL;DR: In this article, the experimental determination of unsaturated optical gain in GaInAs/InP multiple-quantum-well heterostructures is reported, and a step-like line shape of the optical gain spectra is observed, directly reflecting the two-dimensional (2D) nature of the carrier system.
Abstract: The experimental determination of unsaturated optical gain in GaInAs/InP multiple-quantum-well heterostructures is reported. A pronounced step-like line shape of the optical gain spectra is observed, directly reflecting the two-dimensional (2-D) nature of the carrier system. An excellent description of all experimental data is obtained by applying a microscopic theory for the radiative recombination processes. From detailed line shape analyses, two-dimensional carrier densities up to 11*10/sup 2/ cm/sup -2/ and internal absorption coefficients up to 1000 cm/sup -1/ at room temperature are derived. A steep decrease of the differential quantum efficiency above 240 K reveals the importance of intervalence band absorption in quantum-well (QW) lasers. Auger processes are quantitatively investigated in 2-D lasers. The threshold behavior of QW lasers is discussed using the experimentally determined absorption and recombination coefficients, and an optimization of the threshold current density with respect to the number of wells is given. >
TL;DR: Two models based on an atomic medium, one analytic, the other involving numerical simulation of a sequence of pump cycles are considered, and the predictions of both models are shown to agree.
Abstract: We consider the problem of reducing the contributions of pump and spontaneous-emission noise to the output noise of a laser field. We consider two models based on an atomic medium, one analytic, the other involving numerical simulation of a sequence of pump cycles. The predictions of both models are shown to agree. For regular pump excitation the intensity fluctuations of a laser well above threshold may be reduced to zero at the cavity resonance frequency if the ratio of the lifetimes of the upper and lower lasing levels is sufficiently large that spontaneous emission is suppressed. When the atomic lifetimes are comparable, spontaneous emission reduces the amount of noise reduction. For example, for equal atomic lifetimes regular pump excitation will result in a maximum noise reduction in the output field of one-half the shot-noise limit.
15 Feb 1989
TL;DR: In this article, an experiment was conducted in which CO can be excited up to energies of several electronvolts by the absorption of infrared radiation from a relatively low-power CO laser.
Abstract: An experiment is discussed in which CO can be excited up to energies of several electronvolts by the absorption of infrared radiation from a relatively low-power CO laser. Furthermore, experimental results are examined through kinetic modelling. In the experiment, the beam of an intracavity-chopped CO laser operating on all lines at 500 mW and containing a few milliwatts of the fundamental ν= 1→0 band component, is focused into an absorption cell containing a mixture of CO and Ar. The absorption of this infrared radiation is monitored by the optoacoustic effect. A second CO laser operating cw and capable of providing 8 W on all lines but not lasing on the ν= 1→0 band component, is then focused into the same volume in the absorption cell. With both lasers simultaneously focused into the absorption cell, strong fluorescence from the irradiated region is detected by a photomultiplier tube. Modulation of the signal intensity with time is observed, and indicates chemical destruction of the CO in the cell. An analysis and kinetic modelling calculation of this experiment shows that it is possible to excite CO up to high vibrational quantum numbers (ν⩾40) at gas temperatures up to 800 K. by means of CO laser irradiation at the fundamental ν= 1→0 band component. One source responsible for the fluorescence signal observed in the experiment is identified as the 4th positive A 1 Π→X 1 Σ + spontaneous emission. Although the present kinetic model does not incorporate the chemical processes that may lead to the production of additional fluorescing species such as C 2 , good agreement is obtained with the observed fluorescence signal characteristics.
TL;DR: In this article, the fluorescence spectrum of praseodymium in a silica host has been investigated through the direct excitation of the /sup 3/P/sub 0/, /sup 1/D/sub 2/, and 1G/sub 4/ absorption bands, which occur at around 488, 590, and 974 nm, respectively.
Abstract: The fluorescence spectrum of praseodymium in a silica host has been investigated through the direct excitation of the /sup 3/P/sub 0/, /sup 1/D/sub 2/, and 1G/sub 4/ absorption bands, which occur at around 488, 590, and 974 nm, respectively. The observed spontaneous emission consists of four main bands with peaks at 633, 707, 888, and 1080 nm. In each case the level principally responsible for these emissions was found to be 1D/sub 2/. Stimulated emission has been seen for the first time at 888 nm for a threshold of 10 mW absorbed power. In addition, the lasing characteristics at 1080 nm have been investigated. >
TL;DR: In this article, the hydrogen recombination line H53-alpha has been detected in another galaxy: the nearby starburst system M82, and the line strength implies an ionization rate of 1.1 x 10 to the 54th/s, approximately five times larger than that inferred from Br-alpha observations.
Abstract: Emission in the hydrogen recombination line H53-alpha has been detected, for the first time, in another galaxy: the nearby starburst system M82. This line is produced primarily by spontaneous emission and provides the most direct, extinction-independent estimate of the ionization rate in the star-forming complex. The line strength implies an ionization rate of 1.1 x 10 to the 54th/s, approximately five times larger than that inferred from Br-alpha observations, and indicates a dust extinction at 4 microns of more than 1 mag. Comparison of the 3.3 mm free-free continuum and H53-alpha fluxes implies an average electron temperature of about 5000 K. Analysis of the line excitation conditions, using the H53-alpha emission in conjunction with that in the far-IR O(2+) and N(2+) forbidden lines, together with the IR luminosity, suggests that only a very restricted range of stellar masses are formed. 41 refs.
TL;DR: The spectral density of the frequency fluctuations of a diode-pumped single-mode monolithic Nd:YAG ring aser is measured by locking a Fabry-Perot resonator to the laser frequency by measuring the fluctuations near the limit due to spontaneous emission.
Abstract: The spectral density of the frequency fluctuations of a diode-pumped single-mode monolithic Nd:YAG ring laser was measured by locking a Fabry-Perot resonator to the laser frequency. The fluctuations approach the limit due to spontaneous emission (the Schawlow-Townes limit) at frequencies above 80 kHz. The inherent frequency stability of these lasers makes them attractive as a potential light source for gravitational-wave interferometers.
01 Oct 1989
TL;DR: In this paper, a new time-domain model for active mode-locking in semiconductor lasers, coupled to external cavities including a filter, is developed, where the propagating field is considered, rather than the photon density.
Abstract: A new time-domain model for active mode-locking in semiconductor lasers, coupled to external cavities including a filter, is developed. Unlike previous time domain models, the propagating field is considered, rather than the photon density. This allows time-domain filters to be used to model the spectral dependencies of gain, spontaneous emission and dispersive components. Also, Fourier transforms of the field reveal the output spectrum.The new model is compared with results from a previous time-domain model before the effects of bandwidth limiting on pulse shape are investigated. Results show that transform limited pulses can be generated. However, their stability is critically dependent on the drive conditions and the spontaneous emission coupled to the lasing mode.
TL;DR: XeF-doped Ar crystals pumped at 248 nm undergo stimulated emission over the D-X band at 286 nm and Spectral narrowing measurements indicate a net gain in excess of 6 cm(-1).
Abstract: XeF-doped Ar crystals pumped at 248 nm undergo stimulated emission over the D–X band at 286 nm. Spectral narrowing measurements indicate a net gain in excess of 6 cm−1.
TL;DR: A linear quantum theory of two-photon correlated-spontaneous-emission lasers (two-Photon CEL’s) has been formulated recently, which predicts, for the first time, the generation of squeezed states from an active device.
Abstract: A linear quantum theory of two-photon correlated-spontaneous-emission lasers (two-photon CEL’s) has been formulated recently,1 which predicts, for the first time, the generation of squeezed states from an active device. More recently, a nonlinear theory of the two-photon CEL has been developed by using an effective interaction Hamiltonian for a two-photon transition.2
TL;DR: In this article, the radiative recombination is excitonic at 14 K and bimolecular at 200 K and 300 K, respectively, and the interface recombination velocity is lowered by one order of magnitude when the under-confinement layer contains a superlattice.