Showing papers in "IEEE Journal of Quantum Electronics in 1988"
TL;DR: In this article, a table-top-size Nd:glass amplifier was used to amplify single picosecond pulses to the terawatt level by using the technique of chirped pulse amplification.
Abstract: Single picosecond pulses have been amplified to the terawatt level by a table-top-size Nd:glass amplifier by using the technique of chirped pulse amplification (CPA). The divergence of the beam is twice the diffraction limit, making the brightness of this source equal to approximately 2*10/sup +18/ W/(cm-sr), which is thought to be the highest brightness yet reported. The CPA technique allows the efficient energy extraction from extremely compact amplifier systems. Amplification of chirped pulses over nine orders of magnitude, i.e. from nanojoule to the joule level, has been demonstrated. >
801 citations
TL;DR: In this article, photoconducting antennas have been demonstrated which are capable of generating and coherently detecting subpicosecond electrical pulses, when illuminated with femtosecond optical pulses, radiate electrical pulses which have frequency spectra that extend from 2 THz.
Abstract: Photoconducting antennas have been demonstrated which are capable of generating and coherently detecting subpicosecond electrical pulses. These antennas, when illuminated with femtosecond optical pulses, radiate electrical pulses which have frequency spectra that extend from 2 THz. Microscope dipoles measuring 50, 100, and 200 mu m have been fabricated and tested. Integrated photoconductors of radiation-damaged silicon-on-sapphire were used both for impulsive current excitation of the transmitting antennas as well as for gating the receiving antennas. >
774 citations
TL;DR: In this paper, a vertical-cavity surface emitting semiconductor laser was proposed to reduce the threshold current of the laser reflector and introduced a circular buried heterostructure, which is 7 mu m long and 6 mu m in diameter.
Abstract: A description is given of the research progress in developing a vertical-cavity surface-emitting (SE) injection laser based on GaAlAs/GaAs and GaInAsP/InP systems Ultimate laser characteristics, device design, state-of-the-art performances, possible device improvement, and future prospects will also be discussed The authors propose a vertical-cavity surface emitting semiconductor laser To reduce the threshold current, they improved the laser reflector and introduced a circular buried heterostructure The microcavity structure, which is 7 mu m long and 6 mu m in diameter, was realized with a threshold of 6 mA Thus, possibilities of an extremely low threshold current SE laser device and a densely packed two-dimensional array are suggested >
624 citations
TL;DR: Progress in diode lasers and diode laser arrays promises all solid-state lasers in which the flash lamp is replaced by diode Laser for average power levels in excess of tens of watts and at a price that is competitive with flash lamp-pumped laser systems.
Abstract: Recently, interest in diode laser-pumped solid-state lasers has increased due to their advantages over flashlamp-pumped solid-state lasers. A historical overview is presented of semiconductor diode-pumped solid-state lasers beginning with work in the early 1960s and continuing through recent work on wavelength extension of these devices by laser operation on new transitions. Modeling of these devices by rate equations to obtain expressions for threshold, slope efficiency, and figures of merit is also given. >
559 citations
TL;DR: In this article, the time-resolved optical Kerr responses of several simple molecular liquids are probed with 65-fs laser pulses and four dynamically distinct responses associated with the nonlinear susceptibility are observed in every liquid that possesses a permanent anisotropic polarizability.
Abstract: The time-resolved optical Kerr responses of several simple molecular liquids are probed with 65-fs laser pulses. Four dynamically distinct responses associated with the nonlinear susceptibility are observed in every liquid that possesses a permanent anisotropic polarizability. A simple model that specifically includes inertial effects provides an excellent description of the entire temporal profile of the Kerr signal of each liquid investigated. The role of coherent-coupling effects in the interpretation of optical Kerr data is outlined both experimentally and theoretically. >
485 citations
TL;DR: In this article, the factors contributing to system bandwidth, sensitivity, spatial resolution, and circuit perturbation are discussed, as are the circuit requirements for realistic testing of analog and digital devices.
Abstract: Direct electrooptic sampling is a noncontact optical-probing technique for measuring with picosecond time resolution the voltage waveforms at internal nodes within GaAs integrated circuits. The factors contributing to system bandwidth, sensitivity, spatial resolution, and circuit perturbation are discussed, as are the circuit requirements for realistic testing of analog and digital devices. Measurements of high-speed GaAs integrated circuits are presented, including time-domain waveform and timing measurements of digital and analog circuits and frequency-domain transfer function measurements of microwave circuits and transmission structures. >
399 citations
TL;DR: In this paper, a coupled oscillator model is used to predict the limiting speed of response and generation efficiency of different electrooptic materials, including lithium tantalate, when the duration of the exciting femto second optical pulse is comparable to the period of lattice vibrations.
Abstract: Recent work on the generation of ultrashort electrical pulses by optical rectification of femtosecond optical pulses in electrooptic materials is summarized. This technique, which is called electrooptic Cherenkov radiation, is described in detail with particular emphasis on the effects of dispersion due to coupling to lattice vibrational resonances. Recent experimental results in lithium tantalate are described which illustrate these effects. When the duration of the exciting femto second optical pulse is comparable to the period of the lattice vibrations, a pronounced ringing is observed in the electrical waveforms. A coupled oscillator model is used to develop a theory that accurately accounts for these effects and can be used to predict the limiting speed of response and generation efficiency of different electrooptic materials. >
342 citations
TL;DR: In this paper, the basic concepts of sum frequency generation are reviewed and its application to the measurement of time-resolved luminescence spectra with sub-picosecond time resolution is discussed.
Abstract: The basic concepts of sum frequency generation are reviewed and its application to the measurement of time-resolved luminescence spectra with subpicosecond time resolution is discussed. The emphasis is on the discussion of those aspects which are important for the optimization of such an upconversion spectrometer. Results of numerical calculations are presented for various nonlinear crystals, and a recently developed upconversion system is reviewed. This system provides excellent time resolution ( >
342 citations
TL;DR: In this article, an energy transfer upconversion process is identified which leads to a sublinear rise in upper-state population with pump power, and thresholds of 4.4 mW and slope efficiency of 19% have been demonstrated.
Abstract: Spectroscopic measurements and analysis of diode laser-pumped operation of Tm,Ho:YAG at 2.1 mu m at room temperature have been performed. The peak effective stimulated emission cross section is measured to be 9*10/sup -21/ cm/sup 2/ at 2.091 mu m and the upper state lifetime is 8.5 ms. Under diode laser pumping, thresholds of 4.4 mW of absorbed power and slope efficiency of 19% have been demonstrated. Calculations of threshold power are performed based on the spectroscopic measurements. An energy transfer upconversion process is identified which leads to a sublinear rise in upper-state population with pump power. >
313 citations
Journal Article•
TL;DR: The efficacy of tuna fish oil in reducing vulnerability to both ischemic and reperfusion arrhythmias suggests a potential beneficial effect of dietary n-3 fatty acids in addition to their influence on hemostasis, plasma lipids, and atherosclerosis that may contribute to their proposed role in lowering cardiovascular disease mortality and morbidity.
Abstract: Coronary artery occlusion and reperfusion in the anesthetized rat was used as a whole animal model of arrhythmia and sudden cardiac death to examine the influence of long-term dietary lipid modulation of myocardial membrane fatty acids on the development of cardiac arrhythmias. Feeding rats a diet supplemented with tuna fish oil significantly reduced the incidence and severity of arrhythmias, preventing ventricular fibrillation during both occlusion and reperfusion. Dietary sunflower seed oil reduced arrhythmias during occlusion but not in reperfusion. Dietary fat can modify the vulnerability of the myocardium to arrhythmic stimuli. The efficacy of tuna fish oil in reducing vulnerability to both ischemic and reperfusion arrhythmias suggests a potential beneficial effect of dietary n-3 fatty acids in addition to their influence on hemostasis, plasma lipids, and atherosclerosis that may contribute to their proposed role in lowering cardiovascular disease mortality and morbidity.
299 citations
TL;DR: In this paper, the performance of the gallium-doped gallium fluoride garnet, Na/sub 3/Ga/sub 2/Li/ sub 3/F/sub 12/:Cr/sup 3+/, as a laser material has been investigated experimentally.
Abstract: Few of the existing Cr/sup 3+/ vibronic lasers have achieved the slope efficiency and tuning range expected based on their known spectroscopic properties. To discover the cause of this behavior, the performance of chromium-doped gallium fluoride garnet, Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, as a laser material has been investigated experimentally. The data reported include absorption and emission spectra, emission rates, quantum efficiency, laser wavelength tuning range, laser output slope efficiencies, and excited-state absorption spectra. Similar properties of the alexandrite laser material were studied for comparison. The results indicate that the performance of the gallium fluoride garnet laser is severely limited by Cr/sup 3+/ excited-state absorption (ESA). A model is presented to account for the unexpected nature of the ESA, which appears to be a common problem for all Cr/sup 3+/ vibronic lasers. Criteria are suggested for choosing Cr/sup 3+/ hosts for which the effects of ESA will be minimized. >
TL;DR: LiCaAlF/sub 6/:Cr/sup 3+/ (Cr/Sup 3+)/:LiCAF exhibits an intrinsic (extrapolated maximum) slope efficiency of 67%.
Abstract: LiCaAlF/sub 6/:Cr/sup 3+/ (Cr/sup 3+/:LiCAF) exhibits an intrinsic (extrapolated maximum) slope efficiency of 67%. For comparison, the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/ and ScBO/sub 3/:Cr/sup 3+/ were found to be 65, 28, and 26%, respectively. The tuning range of LiCaAlF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well. >
TL;DR: In this article, the effect of external feedback on a single-mode semiconductor laser is estimated by a numerical solution of the nonlinear rate equations, and it is found that the lasing mode with the minimum linewidth is most stable rather than the mode with minimum threshold gain.
Abstract: The effect of external feedback on a single-mode semiconductor laser is estimated by a numerical solution of the nonlinear rate equations. The analysis yields an excellent description of published experimental results. It is found that the lasing mode with the minimum linewidth is most stable rather than the mode with minimum threshold gain. The transition to the coherence-collapse regime is of particular interest. It usually occurs for feedback fractions approximately=10/sup -4/, but it can be shifted to considerably larger feedback levels either by increasing the emitted optical power or the laser length or by decreasing the linewidth enhancement factor alpha . >
TL;DR: In this paper, a theory of external doubling with a resonant fundamental is presented and compared to experimental results for three monolithic cavities of nonlinear MgO:LiNbO/sub 3.
Abstract: 56% efficient external-cavity-resonant second-harmonic generation of a diode-laser pumped, CW single-axial-mode Nd:YAG laser is reported. A theory of external doubling with a resonant fundamental is presented and compared to experimental results for three monolithic cavities of nonlinear MgO:LiNbO/sub 3/. The best conversion efficiency was obtained with a 12.5-mm-long monolithic ring cavity doubler, which produced 29.7 mW of CW, single-axial mode 532-nm radiation from an input of 52.5 mW. >
TL;DR: In this article, a model for spectral-hole burning measurements performed under femtosecond transient excitation and probing is presented, where the pump-induced changes in the spectrum of probe transmittance arise not only from changes in level population (hole burning), but also from the presence of pump polarization during the probe, and from perturbations of the decay of the probe polarization.
Abstract: A model calculation is presented that describes the features of spectral-hole burning measurements performed under conditions of femtosecond transient excitation and probing. Pump-induced changes in the spectrum of probe transmittance arise not only from changes in level population (hole burning), but also from the presence of pump polarization during the probe, and from perturbations of the decay of the probe polarization. These latter effects give rise to oscillating differential transmittance spectra when the (shorter) probe pulse arrives prior to the peak of the pump noise. Only when the probe pulse follows the bulk of the pump pulse does the level population effect dominate the spectrum, so that one can observe dynamic hole-burning effects without distortion. >
TL;DR: Theoretical and experimental results from an injection-locked semiconductor laser are reported in this article, where the authors show that the usefulness of the technique in terms of modulation is estimated based on the behaviour, amplitude, and frequency of the relaxation oscillations which are the main limiting factor.
Abstract: Theoretical and experimental results from an injection-locked semiconductor laser are reported. The measure deposition and size of the locking bandwidth compare favorably to those calculated using the authors' model of the injected laser. The effect of synchronization on the intensity level is pointed out. The usefulness of the technique in terms of modulation is estimated based on the behaviour, amplitude, and frequency of the relaxation oscillations which are the main limiting factor. >
TL;DR: In this paper, a comprehensive model for graded-index, separate-confinement-heterostructure, singlequantum-well (GRIN-SCH-SQW) Al/sub x/Ga/sub 1-x/As diode lasers is presented, and compared with experimental data.
Abstract: A comprehensive model for graded-index, separate-confinement-heterostructure, single-quantum-well (GRIN-SCH-SQW) Al/sub x/Ga/sub 1-x/As diode lasers is presented, and compared with experimental data. The model combines many individual features not heretofore included together, and gives good agreement with gain-vs.-current density data for different structure variations. In addition, the threshold temperature dependence agrees well with data for typical laser conditions, and the high-gain kink in T/sub 0/ versus temperature is qualitatively explained. >
TL;DR: In this paper, a review of the application of phase conjugation to solid-state lasers is presented, using demonstrated techniques for compensating static and thermally induced aberrations and depolarizations, as well as energy scaling by coherent coupling of multiple-gain media.
Abstract: Phase conjugation by stimulated Brillouin scattering represents a fundamentally promising approach for achieving power scaling of solid-state lasers. Following a summary of the power scaling problem and an overview of phase conjugation concepts, a review is presented of the application of phase conjugation to solid-state lasers. The author describes power scaling using demonstrated techniques for compensating static and thermally induced aberrations and depolarizations, as well as energy scaling by coherent coupling of multiple-gain media. Applications to diode-pumped lasers are discussed, as is a novel approach for power scaling of diode lasers themselves. Future research directions are indicated regarding conjugation fidelity at increasingly higher energies or with short-pulse and/or broadband lasers. >
TL;DR: In this paper, an electrooptic method of generating and compressing optical pulses in the picosecond range is described, which is applicable to most CW-ar laser systems.
Abstract: An electrooptic method of generating and compressing optical pulses in the picosecond range is described. The method utilizes electrooptic phase modulation together with group delay/velocity dispersion and is applicable to most CW lasers. From the theoretical analysis, it is shown that normal as well as anomalous dispersion is applicable for pulse compression and that nearly transform-limited pulses can be obtained by the optimum choice of group-delay dispersion. In experiments, pulse compression was utilized for a CW Ar laser using a LiTaO/sub 3/ electrooptic phase modulator with a diffraction grating. Almost transform-limited pulses of 2.1 ps were obtained at 9.35-GHz repetition. The possibility of generating subpicosecond pulses down to several tens of femtosecond pulses is also discussed. >
TL;DR: A survey of results on the development of room-temperature tunable lasers using color centers in ionic crystals and on using color center crystals as nonlinear filters and passive Q switches for neodymium lasers is presented in this article.
Abstract: A survey of results is presented on the development of room-temperature tunable lasers using color centers in ionic crystals and on using color center crystals as nonlinear filters and passive Q switches for neodymium lasers. >
TL;DR: In this paper, it is demonstrated that near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations and a kink is observed in the light-current characteristic.
Abstract: Near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations. In the same region, a kink is observed in the light-current characteristic. Here it is demonstrated that these nonlinear phenomena are predicted by a noise driven multimode traveling-wave model. The dynamics of the low-frequency fluctuations are explained qualitatively in terms of bistability through an iterative description. >
TL;DR: In this article, a many-body calculation of the electron-hole correlation enhancement is presented, which identifies this peak with the Mahan exciton, the result of the Coulomb interaction between the photoexcited hole in the valence band and the sea of electrons in the conduction band.
Abstract: The temperature-dependent optical absorption and luminescence spectra of GaAs/AlGaAs and InGaAs/InAlAs n-doped modulation-doped quantum wells is discussed with emphasis on the peak seen at the edge of the absorption spectra of these samples A many-body calculation of the electron-hole correlation enhancement is presented, which identifies this peak with the Mahan exciton-the result of the Coulomb interaction between the photoexcited hole in the valence band and the sea of electrons in the conduction band This calculation accounts for the strong dependence of the absorption edge peak on both the temperature and carrier concentration, in good qualitative agreement with experimental data and with previously published results The changes induced by the carriers on the subband structure through self-consistent calculations are also analyzed, and it is concluded that in these symmetric structures, the changes are small for achievable carrier densities >
TL;DR: In this article, the optical gain of arrays of quantum boxes is computed, taking into account the inhomogeneous broadening of the gain spectrum resulting from fabricational variations in quantum box size and shape.
Abstract: Lower and upper limits on size are established for quantum boxes. The lower limit is shown to result from a critical size below which electronic states no longer exist. This critical size is different for electrons and holes. The optical gain of arrays of quantum boxes is computed, taking into account the inhomogeneous broadening of the gain spectrum resulting from fabricational variations in quantum box size and shape. >
TL;DR: In this paper, the femtosecond time-resolved observations of coherent molecular vibrations are carried out through impulse-stimulated Raman scattering (ISRS), where individual cycles of vibrational oscillation, as well as vibrational dephasing, are time resolved.
Abstract: Femtosecond time-resolved observations of coherent molecular vibrations are carried out through impulse-stimulated Raman scattering (ISRS). Individual cycles of vibrational oscillation, as well as vibrational dephasing, are time resolved. ISRS therefore provides a means through which time-resolved spectroscopy of vibrationally distorted molecules can be carried out. Several experimental configurations involving either crossed excitation pulses or a single excitation pulse are discussed theoretically and demonstrated experimentally. >
TL;DR: In this paper, a numerical technique that allows straightforward determination of bound-state and quasi-bound-state energy eigenvalues (and lifetimes of the latter) for arbitrary one-dimensional potentials is presented.
Abstract: A numerical technique that allows straightforward determination of bound-state and quasi-bound-state energy eigenvalues (and lifetimes of the latter) for arbitrary one-dimensional potentials is presented. The method involves straightforward multiplication of 2*2 matrices and does not involve any iterations. The applicability of the technique to analysis of the quantum-well structures is also shown. Since the Schroedinger equation for a spherically symmetric potential can be transformed to a one-dimensional equation, all such problems can also be solved using this method. >
TL;DR: In this article, the authors used a compound parabolic concentrator to increase the solar radiation coupled into the laser rod, and showed that existing laser materials with broadband absorption characteristics (e.g. alexandrite and Nd:Cr:GSGG) have a potential for better than 10% overall conversion efficiency when solar-pumped.
Abstract: Results are presented for direct solar pumping of a Nd:YAG rod laser. Stable CW output of more than 60 W was obtained with a slope efficiency exceeding 2%. A compound parabolic concentrator, designed to increase the solar radiation coupled into the laser rod, was used in these experiments. The results are consistent with predictions based on a single solar-pumped laser model, which is also presented. Using this model, it is shown that existing laser materials with broadband absorption characteristics (e.g. alexandrite and Nd:Cr:GSGG) have a potential for better than 10% overall conversion efficiency when solar-pumped. >
TL;DR: In this paper, it is shown that if the field strength is less than a so-called delocalization border, the distribution over unperturbed levels is exponential in the number of absorbed photons and the corresponding localization length is determined.
Abstract: The quantum localization phenomenon that strongly limits any quantum process of diffusive ionization that may be started in systems subjected to a periodic perturbation is discussed. In the case of a highly excited hydrogen atom in a monochromatic field, this phenomenon is theoretically analyzed by reducing the dynamics to appropriate mappings. It is shown that if the field strength is less than a so-called delocalization border, the distribution over unperturbed levels is exponential in the number of absorbed photons and the corresponding localization length is determined. Using the mapping description, it is shown that the excitation process occurring in a two-dimensional atom proceeds essentially along the same lines as in the one-dimensional model. These predictions are supported by results of numerical simulation, and the possibility of their experimental verification is discussed. >
TL;DR: In this paper, lead salt (IV-VI) compounds have been grown epitaxially by a variety of growth techniques, such as molecular-beam epitaxy and hot-wall epitaxy.
Abstract: Lead salt (IV-VI) compounds have been grown epitaxially by a variety of growth techniques, such as molecular-beam epitaxy and hot-wall epitaxy. Recently, compositional superlattices and quantum-well heterostructures have been grown that exhibit strong quantum optical effects. These structures have been used to fabricate midinfrared diode lasers with greatly improved operating temperatures. Thus, it appears that these devices will continue to maintain a significant advantage over II-VI and III-V compound diode lasers. Doping superlattices have been made which possess enhanced minority carrier properties. Ferromagnetic ordering in PbSnTe-MnTe alloys suggests potential areas for future work in magnetic field sensitivity devices. Lead salt quantum-effect structures are included. >
TL;DR: In this paper, the optical gain and the refractive index change of a uniaxially stressed GaAs-Al/sub 2/Ga/sub 1-x/As quantum-well laser were studied theoretically using the multiband effective mass theory (k-p method) and density matrix formalism with intraband relaxations.
Abstract: The optical gain and the refractive index change of a uniaxially stressed GaAs-Al/sub 2/Ga/sub 1-x/As quantum-well laser is studied theoretically using the multiband effective mass theory (k-p method) and density matrix formalism with intraband relaxations. It is found that uniaxial strain of the quantum well substantially alters the subband structures and the optical gain of the quantum-well laser. In particular, the gain of the TM mode increases while the gain of the TE mode decreases with increasing stress. Thus, the threshold current either decreases or increases with the stress, depending on whether the laser is operating in a TM or TE mode. >
TL;DR: By inclining the active stripe of a planar AlGaAs double heterojunction structure by 5 degrees with respect to the facets, reflection feedback has been eliminated and high-power superluminescent diodes emitting 28 mW with less than 5% spectral modulation have been obtained.
Abstract: By inclining the active stripe of a planar AlGaAs double heterojunction structure by 5 degrees with respect to the facets, reflection feedback has been eliminated and high-power superluminescent diodes emitting 28 mW with less than 5% spectral modulation have been obtained. >