Showing papers on "Laser published in 1984"
Book•
01 Jan 1984
TL;DR: In this article, the authors present an analysis and interpretation of the Lidar Return Signals, as well as a discussion of the application of LIDAR in hydrographic and atmospheric applications.
Abstract: Electromagnetic Theory of Radiation. Quantum Physics and Radiation Processes. Interaction and Propagation of Radiation. Laser Fundamentals. Laser Systems as Remote Sensors. Laser-Remote-Sensor Equations. Analysis and Interpretation of the Lidar Return Signals. Atmospheric Lidar Applications. Hydrographic Lidar Applications. Concluding Remarks. Index.
717 citations
TL;DR: Numerical calculations have investigated the possibility of developing soot diagnostics based on laser heating of the soot particles using the laser-modulated incandescence of the particles and the direct detection of the evaporated C2 molecules.
Abstract: Through numerical calculations we have investigated the possibility of developing soot diagnostics based on laser heating of the soot particles. Two strategies, one using the laser-modulated incandescence of the particles, and the other using direct detection of the evaporated C2 molecules, were examined. Both strategies can yield size distribution and volume fraction information provided the laser wavelength is near the graphite absorption band at 260 nm; otherwise, only volume fractions can be obtained.
545 citations
[...]
AT&T1
TL;DR: The soliton laser as discussed by the authors is a mode-locked laser using pulse compression and solitons in a single-mode fiber to force the laser itself to produce pulses of a well-defined shape and width.
Abstract: The soliton laser, a novel concept in ultrashort-pulse lasers, is a mode-locked laser using pulse compression and solitons in a single-mode fiber to force the laser itself to produce pulses of a well-defined shape and width. Thus the fiber is in one way or another involved in the laser’s feedback loop. Although the basic concept is a general one, we report here primarily on the first successful version[1], based on a sync-pumped, mode-locked color-center laser operating in the 1.5 pm region. To date this color-center soliton laser has directly produced pulses as short as 130 fsec, and has allowed for the production of pulses of as little as 50 fsec FWHM, by compression in a second, external fiber. Other advantages include wide tunability (limited only by power requirements for soliton production in the fiber), output pulses that are always transform limited, easy adjustment for production of ~sech2 pulse shape. and a relative simplicity of construction.
464 citations
TL;DR: In this article, high-intensity, 75-fs optical pulses have been applied to observe multiphoton and thermally enhanced photoemission from a tungsten metal surface.
Abstract: High-intensity, 75-fs optical pulses have been applied to observe multiphoton and thermally enhanced photoemission from a tungsten metal surface. Experimental results suggest the presence of anomalous heating, a transient nonequilibrium temperature difference between the electrons and lattice. Pump-probe measurements indicate an electron-phonon energy relaxation time of several hundred femtoseconds.
439 citations
435 citations
TL;DR: In this article, a laser-generated spark was used to analyze liquids spectroscopically for elemental constituents, and limits of detection for Li, Na, K, Rb, Cs, Be, Mg, Ca, B, and Al were established with the use of a 10 Hz repetitive single spark (RSS).
Abstract: A laser-generated spark was used to analyze liquids spectroscopically for elemental constituents. The spark was produced directly in liquids by a focused laser pulse of 15 ns duration and an energy of about 45 mJ/pulse. The size, temperature, and electron density of the spark are reported. Emissions from once-ionized and neutral atoms and simple molecules were observed. Limits of detection for Li, Na, K, Rb, Cs, Be, Mg, Ca, B, and Al in aqueous solutions were established with the use of a 10 Hz repetitive single spark (RSS). Most of these elements were only detectable at levels above 1 μg/mL, although the detection limit for Li was 0.006 μg/mL. The relative standard deviation for replicate sample analysis was 4-8%. The detectability of some species was enhanced with the use of a 10 Hz repetitive spark pair (RSP): a pair of sparks separated in time by about 18 μs. The detection limits for B/H2O with the RSP and the RSS were 80 and 1200 μg/mL, respectively. Species were also detected in organic solvents and in flowing samples. The laser spark method of liquid analysis would be useful in situations requiring noninvasive monitoring of species at high or moderate concentrations.
406 citations
TL;DR: It is shown that the broadening in the far-field beam divergence, as well as the broadens of each of the longitudinal modes that were observed in phase-locked arrays, may arise from the excitation of an increasing number of supermodes at increasing pumping levels.
Abstract: The optical characteristics of phase-locked semiconductor laser arrays are formulated in terms of the array supermodes, which are the eigenmodes of the composite-array waveguide, by using coupled-mode theory. These supermodes are employed to calculate the near fields, the far fields, and the difference in the longitudinal-mode oscillation wavelengths of the array. It is shown that the broadening in the far-field beam divergence, as well as the broadening of each of the longitudinal modes that were observed in phase-locked arrays, may arise from the excitation of an increasing number of supermodes at increasing pumping levels.
404 citations
TL;DR: Inelastic emission characteristics from individual ethanol droplets (60-microm diameter) containing Rhodamine 6G dye and pumped by a cw laser and confirmed by noting the spectral, temporal, and output-versus-input intensity behavior.
Abstract: Inelastic emission characteristics from individual ethanol droplets (60-microm diameter) containing Rhodamine 6G dye and pumped by a cw laser (514.5 nm) were investigated. Laser emission was confirmed by noting the spectral, temporal, and output-versus-input intensity behavior. The liquid-air boundary of the droplets provides the optical feedback at selected wavelengths corresponding to the morphology-dependent resonances of a spherical droplet.
386 citations
Proceedings Article•
[...]
TL;DR: By incorporating a length of single-mode, polarization-preserving fiber into the feedback loop of a mode-locked color-center laser (lambda~1.4-1.6 microm), a device that is called the soliton laser is created.
Abstract: The soliton laser1 is a novel mode-locked device employing a length of single-mode fiber in its feedback loop. Its pulse width can be made to have any desired value, down to a small fraction of a picosecond, through choice of the fiber’s length. Operation is based on the ability of single-mode fibers, in the region (λ> 1.3 µm) of negative group-velocity dispersion, to support periodic soliton pulses, as well. as to narrow broader-pulses of the same energy.2,3 As the fiber is the all-important control element, pulse shape and width are largely independent of factors, such as details of gain dynamics and pump pulse width, that are normally of prime importance in mode-locked lasers.
361 citations
TL;DR: In this paper, a nonperturbative theory for free-free transitions of electrons colliding with atoms in intense high-frequency laser fields is developed, where the energy of the incoming electrons is assumed to be smaller than that of the photons.
Abstract: A nonperturbative theory is developed for free-free transitions of electrons colliding with atoms in intense high-frequency laser fields. The energy of the incoming electrons is assumed to be smaller than that of the photons. Rather simple expressions are derived for the multiphoton absorption amplitudes. Large deviations from the laser-free case are shown to appear in elastic scattering. The theory applies at already existing laser frequencies but extends beyond, to the extreme ultraviolet range.
357 citations
TL;DR: In this paper, the inherent connection between frequency deviations and the optical power wave-form of a directly modulated semiconductor laser was derived, providing for the first time a quantitative assessment of inherent optical fiber dispersion penalties.
Abstract: Relations are derived concerning the inherent connection between frequency deviations and the optical power wave-form of a directly modulated semiconductor laser, providing for the first time a quantitative assessment of inherent optical fibre dispersion penalties of directly modulated lasers. The relations also indicate that control of chirp involves only the control of the intensity modulation characteristics and proper current drive of semiconductor lasers. Experimental measurement of FM and IM characteristics of a 1.55 μm DFB laser support the results.
TL;DR: In this article, a detailed theoretical description of the thermal, stress, and beam propagation characteristics of a slab laser is presented, which includes consideration of the effects of the zig-zag optical path.
Abstract: Slab geometry solid-state lasers offer significant performance improvements over conventional rod geometry lasers. We present a detailed theoretical description of the thermal, stress, and beam propagation characteristics of a slab laser. Our analysis includes consideration of the effects of the zig-zag optical path which eliminates thermal and stress focusing and reduces residual birefringence.
TL;DR: In this paper, the mechanisms responsible for the growth of periodic surface structure on Ge irradiated by 1.06-m laser pulses from a single beam are investigated using time-resolved diffraction of a weak cw probe beam from the developing structures, coupled with electron-microscope pictures of the resulting morphology.
Abstract: The mechanisms responsible for the growth of periodic surface structure on Ge irradiated by 1.06-\ensuremath{\mu}m laser pulses from a single beam are investigated. Time-resolved diffraction of a weak cw probe beam from the developing structures, coupled with electron-microscope pictures of the resulting morphology, is used to identify four distinct regimes of ripple formation at different incident laser fluences. At low fluences, the structure develops when thin (1 \ensuremath{\mu}M wide) isolated, molten strips resolidify on the solid substrate, while at high fluences, the structure results from freezing of capillary waves which are generated on the surface that the laser pulse has melted uniformly. Models are presented which clearly demonstrate how the incident electromagnetic field interacts with the evolving structures (in different fluence regimes) to provide feedback mechanisms which sustain their growth.
TL;DR: In this article, a coupledmode analysis has been developed to describe the output of phase-locked injection laser arrays, showing that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters.
Abstract: A coupled‐mode analysis has been developed to describe the output of phase‐locked injection laser arrays. We show that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled‐mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far‐field lobe(s) widths and those predicted by simple diffraction theory.
Book•
01 Jan 1984
TL;DR: In this article, the authors discuss propagation in dielectric waveguides material dispersion total dispersion in multimode and monomode fibres attenuation mechanisms in optical fibres inelastic scattering and non-linear propagation effects system considerations electromagnetic wave propagation in step-index fibre wave and ray propagation in graded-index fibres single-mode fibres the fabrication of fibres, cables and passive components fibre parameters specification and measurement.
Abstract: Part 1 Elementary discussion of propagation in dielectric waveguides material dispersion total dispersion in multimode and monomode fibres attenuation mechanisms in optical fibres inelastic scattering and non-linear propagation effects system considerations electromagnetic wave propagation in step-index fibre wave and ray propagation in graded-index fibres single-mode fibres the fabrication of fibres, cables and passive components fibre parameters specification and measurement. Part 2 Sources and detectors basic semiconductor properties injection luminescence the design of LEDS for optical communication the basic principles of laser action semiconductor lasers semiconductor lasers for optical fibre communication systems semiconductor photodiode detectors avalanche photodiode detectors and photomultiplier tubes. Part 3 The receiver amplifier the regeneration of digital signals coherent systems unguided optical communication systems optical fibre communication systems.
TL;DR: In this article, the authors proposed a phase-locking approach to phase-lock particles in a wave driven by resonantly beating two laser beams in a high-density plasma, which can produce ultrahigh electric fields that propagate with velocities close to c.
Abstract: Space-charge waves driven by resonantly beating two laser beams in a high-density plasma can produce ultrahigh electric fields that propagate with velocities close to c. By phase-locking particles in such a wave, particles may be accelerated to very high energies within a very short distance.
TL;DR: Recent studies indicate that lasers at specific wavelengths and energy densities modulate the connective tissue metabolism by skin fibroblasts both in vitro and in vivo, and suggest the potential role of lasers in the treatment of cutaneous disorders.
Abstract: Various laser modalities are currently in extensive use in dermatology and plastic surgery, particularly for treatment of vascular and pigmented lesions. A relatively new area of laser utilization involves the possible biologic effects of the lasers. In this overview, we are summarizing our recent studies, which indicate that lasers at specific wavelengths and energy densities modulate the connective tissue metabolism by skin fibroblasts both in vitro and in vivo. Specifically, the neodymium-yttrium-aluminum-garnet (Nd: YAG) laser was shown to selectively suppress collagen production both in fibroblast cultures and in normal skin in vivo, thus suggesting that this laser modality may be useful for the treatment of fibrotic conditions such as keloids and hypertrophic scars. Furthermore, two low-energy lasers, helium-neon (He-Ne) and gallium-arsenide (Ga-As), were shown to stimulate collagen production in human skin fibroblast cultures, suggesting that these lasers could be used for enhancement of wound healing processes. These experimental approaches illustrate the future possibilities for applying lasers for the modulation of various biologic functions of cells in tissues and attest to the potential role of lasers in the treatment of cutaneous disorders.
TL;DR: In this paper, the translational energy, angular distribution, rotational alignment, and internal state distribution (vibration, rotation, spin-orbit components and the Λ doublets) are probed through the OH A-X system.
Abstract: Trans‐HONO is optically prepared in specific −N=O stretching vibrational levels (2n, n=1,2,3) of the A state at 369, 355, and 342 nm. The ejected OH fragment is completely characterized by Doppler and polarization laser excitation spectroscopy. In this manner the OH translational energy, angular distribution, rotational alignment, and internal state distribution (vibration, rotation, spin‐orbit and Λ‐doubling components) are probed through the OH A–X system. The OH fragment is found to be translationally hot (∼0.5 eV) with a nearly sin2 θ angular distribution about the electric vector of the photolysis laser. The corresponding line shapes are Doppler split. However, the line shapes and widths do not noticeably depend on either fragment rotation or parent vibration. The internal motion of the OH fragment is vibrationally and rotationally cold; the spin‐orbit components and the Λ doublets are not in equilibrium. The OH fragment is aligned and its π lobe lies preferentially in the plane of rotation. With in...
TL;DR: In this paper, the effect of external optical feedback on the linewidth of a single-mode injection laser is considered theoretically, and a set of three rate equations with Langevin noise sources is used to obtain the power spectrum.
Abstract: The effect of external optical feedback on the linewidth of a single-mode injection laser is considered theoretically. A set of three rate equations with Langevin noise sources is used to obtain the power spectrum. If the high-frequency structure in the power spectrum is ignored, the line shape is Lorentzian and exhibits broadening or narrowing depending on the external-cavity phase shift. Particular attention is paid to the line narrowing after including the effect of carrrier-induced index changes.
Book•
01 Jan 1984
TL;DR: The components of Theoretical Spectroscopy are discussed in this paper, where the effects of strong fields on matter are discussed as well as the effect of field fluctuation on Spectrograms.
Abstract: The Components of Theoretical Spectroscopy. Physical Effects of Strong Fields on Matter. Foundation of Laser Theory. Topics in Laser Spectroscopy. Effects of Field Fluctuations on Spectroscopy. Elements of Electromagnetic Field Quantization. References. Index.
TL;DR: In this article, a detailed theoretical analysis of stability for a semiconductor laser in an external cavity is presented, where the limits of stable operation are determined as a function of the external cavity parameters and the linewidth enhancement factor α.
Abstract: A detailed theoretical analysis of stability is presented for a semiconductor laser in an external cavity. The limits of stable operation are determined as a function of the external cavity parameters and the linewidth enhancement factor α. Instability is related to jumps of the laser frequency between external cavity modes (frequency bistability) or to feedback-induced intensity pulsations due to the carrier density dependence of the refractive index. The limit of bistability is derived from the steady-state solutions of the rate equations and the intensity pulsation limit is obtained from a small-signal analysis. This analysis also gives the location of zeros in the system determinant and the resulting FM noise spectrum. For practical applications we emphasize the determination of the stable tuning range for the phase in the external cavity and the classification of the possible types of instability for various feedback levels.
TL;DR: Pulses of 90-fsec duration from a cavity-dumped colliding-pulse mode-locked laser have been amplified to microjoule energies at 5-kHz repetition rate using a copper-vapor-laser pump source.
Abstract: Pulses of 90-fsec duration from a cavity-dumped colliding-pulse mode-locked laser have been amplified to microjoule energies at 5-kHz repetition rate using a copper-vapor-laser pump source. Near-diffraction-limited focusing and efficient femtosecond continuum generation are demonstrated.
Patent•
17 Jul 1984
TL;DR: In this paper, a medical and surgical laser probe comprised of a quartz optical fiber and a laser rod member optically connected with an artificial saphire has been presented, which has a tapered portion so as to emit the incident laser beam from the tip end of the rod member without leaking it out from the tapered face.
Abstract: A medical and surgical laser probe comprised of a quartz optical fiber and a laser rod member optically connected thereto which is made of an artificial saphire and has a tapered portion so as to emit the incident laser beam from the tip end of the rod member without leaking it out from the tapered face. With this laser probe, laser irradiation in contact with the tissue is enabled and any desired medical and surgical treatment such as incision, coagulation, hemostasis can be attained effectively.
TL;DR: In this article, the attenuation attenuation (ATN) of visible light as it passes through filter samples was measured for a large number of solvent-extracted source and ambient particle samples using temperature-programmed evolved gas analysis with continuous light attenuation measurement.
TL;DR: In this article, the dynamic behavior of an homogeneously broadened laser with injected signal is analyzed for a model in which the polarization is adiabatically eliminated. And the authors show that a transition to chaos via intermittency is possible for parameters appropriate for CO2 lasers.
TL;DR: In this article, the influence of quantum phase fluctuations which affect single frequency semiconductor lasers in various coherent detection systems is discussed in terms of photocurrent autocorrelation and spectral density functions.
Abstract: The influence of quantum phase fluctuations which affect single frequency semiconductor lasers in various coherent detection systems is discussed in terms of photocurrent autocorrelation and spectral density functions. The general treatment given in this paper can be applied in diverse practical cases and points out the problems of phase correlation and phase matching between the two mixed optical beams. In the more general case the photocurrent spectrum is found to be composed of discrete and quasi-Lorentzian parts whose energies and spectral spreads are discussed as a function of the laser line width, the phase matching and the phase correlation between the two coherently combined fields.
TL;DR: In this paper, a frequency-multiplied Nd:YAG laser, 355 m wavelength, 5 ns pulse duration, punches a self-healing hole of submicrometer aperture in cell membrane under selected irradiation conditions.
Abstract: A new technique is presented to incorporate exogeneous gene materials (DNA) into cells with a microbeam irradiation from an uv pulsed laser. A frequency-multiplied Nd:YAG laser, 355 m wavelength, 5 ns pulse duration, punches a self-healing hole of submicrometer aperture in cell membrane under selected irradiation conditions. It takes a fraction of a second for the aperture to close, long enough to allow the foreign DNA, contained in the medium, to slip into the cell. The method offers a clear advantage over existing methods: increases the success rate of DNA transfection as well as the efficiency of cell modification by orders of magnitude.
TL;DR: In this paper, the high-frequency modulation characteristics of InGaAsP ridge waveguide and etched mesa buried heterostructure (EMBH) laser at 1.55 μm and 1.3 μm are investigated.
Abstract: The high-frequency modulation characteristics of InGaAsP ridge waveguide lasers at 1.55 μm and etched mesa buried heterostructure (EMBH) lasers at 1.3 μm are investigated. Small-signal and large-signal circuit models are developed for both devices, and the main factors which influence the high-frequency modulation response are established. It is shown that the electrical parasitics in the chip dominate the small-signal frequency response of the EMBH laser and limit the large-signal turn-on and turn-off times. The small-signal and large-signal responses of both devices show strong damping of the relaxation oscillations. This damping can be modeled accurately using field-dependent optical gain compression in the rate equations.
TL;DR: In this article, the lumiere laser and the diffusion Raman ont pour support des fibres optiques, which permet des analyses dans des environnements hostiles.
Abstract: Description d'un systeme dans lequel la lumiere laser et la diffusion Raman ont pour support des fibres optiques. Cette technique permet des analyses dans des environnements hostiles
TL;DR: By using a GaAs/GaAIAs multiple-quantum-well sample as a saturable absorber in an external resonator, it is shown that pulses as short as 1.6 psec are observed, the shortest pulses ever observed to the authors' knowledge from a mode-locked diode laser in a regulator pulse train.
Abstract: By using a GaAs/GaAIAs multiple-quantum-well sample as a saturable absorber in an external resonator, we have passively mode locked a GaAs laser to obtain pulses as short as 1.6 psec, the shortest pulses ever observed to our knowledge from a mode-locked diode laser in a regulator pulse train.