Showing papers on "Laser published in 1978"
TL;DR: In this paper, the observation of photosensitivity in Ge-doped core optical fibers is reported. The photosensitivity is manifested by light-induced refractive index changes in the core of the waveguide.
Abstract: The observation of photosensitivity in Ge‐doped core optical fibers is reported. The photosensitivity is manifested by light‐induced refractive‐index changes in the core of the waveguide. Narrowband reflectors in a guide structure have been fabricated using this photosensitivity and the resulting DFB reflectors employed as laser mirrors in a cw gas laser in the visible.
2,294 citations
TL;DR: A simplified version of the side-pumped pulsed dye laser which has a spectral halfwidth of 1.25 GHz and a peak power of 10 kW at 600 nm and is exceptionally easy to align is developed.
Abstract: We have developed a simplified version of the side-pumped pulsed dye laser which has a spectral halfwidth of 1.25 GHz and a peak power of 10 kW at 600 nm. The basic laser consists of only four components (output mirror, dye cell, diffraction grating, and tuning mirror) and is exceptionally easy to align. Since the beam expander has been eliminated, the laser cavity can be made quite compact. Under the condition of reduced gain, the laser has been operated in a single mode.
664 citations
TL;DR: A form of coherent trapping that occurs when multiple resonant laser beams are used to couple the various ground states to a common upper level is described, which prevents the extraction of the entire population.
Abstract: It is often desirable in laser spectroscopy and isotope separation to extract as much as possible of an atomic or molecular population that is distributed among a number of ground-state sublevels and low-lying metastable levels. We describe a form of coherent trapping that occurs when multiple resonant laser beams are used to couple the various ground states to a common upper level. This effect prevents the extraction of the entire population. We then study the effect with two dye lasers and an atomic beam and suggest possible ways to maximize the pumping efficiency.
536 citations
01 Jan 1978
TL;DR: The classical theory of wave propagation in a turbulent medium has been studied in this article, with the focus on the propagation of optical waves in turbulent medium and similarity relations for strong intensity fluctuations of laser radiation.
Abstract: The classical theory of wave propagation in a turbulent medium- Modern theories in the propagation of optical waves in a turbulent medium- Similarity relations and their experimental verification for strong intensity fluctuations of laser radiation- The beam wave case and remote sensing- Imaging and optical communication through atmospheric turbulence- Thermal blooming in the atmosphere
465 citations
TL;DR: In this article, the 2P1/2→2P3/2 transition of the iodine atom was achieved by energy transfer from the 1Δ metastable state of O2.
Abstract: cw laser action was achieved on the 2P1/2→2P3/2 transition of the iodine atom by energy transfer from the 1Δ metastable state of O2. The excited oxygen was generated chemically by flowing chlorine gas through a basic solution of 90% H2O2. The effluent from the oxygen generator was mixed with molecular iodine at the entrance of a longitudinal flow laser cavity where the I2 was dissociated by a small amount of O2(1Σ) that was present in the flow due to energy pooling processes. The measured output power was greater than 4 mW.
418 citations
Book•
01 Dec 1978TL;DR: In this article, the authors present a survey of the current state of the art in the field of laser technology. But they do not consider the application of laser technologies in the context of mask production.
Abstract: Preface. Acknowledgments. Historical Prologue: Fundamentals of Lasers. Electromagnetic Radiation. Elementary Optical Principles. Energy Levels. Interaction of Radiation and Matter. Laser Materials. Population Inversion. Resonant Cavity. Selected References.Properties of Laser Light: Linewidth. Beam Divergence Angle. Spatial Profiles of Laser Beams. Temporal Behavior of Laser Output. Coherence. Radiance. Focusing Properties of Laser Radiation. Power. References. Selected Additional References. Practical Lasers: Gas Lasers. Solid State Lasers. Semiconductor Lasers. Organic Dye Lasers. References. Selected Additional References. Trends in Laser Development: Semiconductor Lasers. Diode-Pumped Solid State Tunable Lasers. Chemical Lasers. Free Electron Lasers. X-Ray Lasers. References. Selected Additional References. Laser Components and Accessories: Mirrors. Optics. Polarizers. Infrared Materials. Detectors. Modulators. Light Beam Deflectors. Q-Switches. Nonlinear Optical Elements. Optical Isolators. Raman Shifters. Injection Seeders. Beam Profilers. Optical Tables. Spatial Light Modulators. Beam Homogenizers. Selected References. Care and Maintenance of Lasers: Damage and Deterioration of Lasers.Care and Maintenance. References. Selected Additional References. Laser Safety: Physiological Effects. Laser Safety Practices and Standards. References. Selected Additional References. Alignment, Tooling and Angle Tracking: Position-SensitiveDetectors. Laser Tooling. Angle Tracking. Lasers in Construction. References. Selected Additional References. Principles Used in Measurement: The Michelson Interferometer. Beat Production (Heterodyne). The Doppler Effect. Coherence Requirements. Selected References.Distance Measurement and Dimensional Control: Interferometric Distance Measurement. Laser Doppler Displacement. Beam Modulation Telemetry. Pulsed Laser Range Finders. A Laser Interferometer Application in Mask Production: A Specific Example of Distance Measurement and Dimensional Control. References. Selected Additional References. Laser Instrumentation and Measurement: Velocity Measurement. Angular Rotation Rate. Diffractive Measurement of Small Dimension: Wire Diameter. Profile and Surface Position Measurement. Measurement of Product Dimension. Measurement of Surface Finish. Particle Diameter Measurement. Strain Measurement. Vibration. Cylindrical Form Measurement. Defect Detection. Surface Flaw Inspection Monitor-A Specific Example. Summary. References. Selected Additional References. Interaction of High-Power Laser Radiation with Materials: References. Selected Additional References. Laser Applications in Material Professing: Selected References. Applications of Laser Welding: Seam Welding-Subkilowatt Levels. Welding with Multikilowatt Lasers Spot Welding. Specific Examples of Laser Welding Capability. Summary. References. Selected Additional References. Applications for Surface Treatment: Hardening. Glazing. Laser Alloying. Laser Cladding. Specific Examples of Laser Heat Treating Capability. References. Selected Additional References. Applications for Material Removal: Drilling, Cutting, Marking: Laser-Induced Material Removal. Hole Drilling. Cutting. Scribing. Marking. Balancing. Paint Stripping. Laser Deposition of Thin Films. Specific Examples of Material Removal. References. Selected Additional References. Lasers in Electronic Fabrication: Established Applications in Electronics.Applications in Integrated Circuit Fabrication. Summary. A Specific Example-Laser-Based Photomask Repair. References. Selected Additional References. Principles of Holography: Formation of Holograms. The Holographic Process. Hologram Types and Efficiency. Practical Aspects of Holography. References. Selected Additional References. Applications of Holography: Holographic Interferometry. A Miscellany of Applications. Holographic Optical Elements. An Example of Holographic Application. References. Selected Additional References. Laser Applications in Spectroscopy: Lasers for Spectroscopic Applications. Types of Laser Spectroscopy. Applications of Laser Spectroscopy. References. Selected Additional References. Chemical Applications: Laser-Initiated Reactions. Laser-Altered Reactions. Laser Monitoring of Chemical Dynamics. Isotope Separation. References. Selected Additional References. Fiber Optics:References. Selected Additional References. Integrated Optics: Optical Waveguides. Components for Integrated Optics. Integrated Optic Circuits. Applications. References. Selected Additional References. Information Related Applications of Lasers: Lightwave Communications. Optical Data Storage. Optical Data Processing. Laser Graphics. Consumer Products. References. Selected Additional References. Epilogue--A Look at the Future. References. Selected Additional References.
326 citations
TL;DR: A variation of the grazing-incidence pulsed dye laser is presented that has been operated in a single longitudinal cavity mode with a single-shot linewidth of less than 300 MHz and a time-averaged linewitzer of 750 MHz.
Abstract: A variation of the grazing-incidence pulsed dye laser is presented. This laser has been operated in a single longitudinal cavity mode with a single-shot linewidth of less than 300 MHz and a time-averaged linewidth of 750 MHz. The single-mode conversion efficiency of the laser is 2% using Rhodamine 6G dye.
239 citations
01 Dec 1978
TL;DR: In this article, various factors that can effect thermal blooming in stagnation zone situations are examined, including stagnation-zone motion, longitudinal air motion in the neighborhood of the stagnation zone, and the effects of scenario noncoplanarity.
Abstract: Various factors that can effect thermal blooming in stagnation zone situations are examined, including stagnation-zone motion, longitudinal air motion in the neighborhood of the stagnation zone, and the effects of scenario noncoplanarity. Of these effects, only the last offers reasonable hope of reducing the strong thermal blooming that normally accompanies stagnation zones; in particular, noncoplanarity should benefit multipulse more than cw beams. The methods of treating nonhorizontal winds hydrodynamically for cw and multipulse steady-state sources are discussed. Aspects of pulse “self-blooming” are also considered.
234 citations
TL;DR: In this paper, the authors reported the generation of 20-ps optical pulses at microwave repetition rate from a GaAlAs double-heterostructure diode operating at room temperature.
Abstract: We report the generation of 20‐ps optical pulses at microwave repetition rate from a GaAlAs double‐heterostructure diode operating cw at room temperature The diode is operated in an external optical resonator and is actively modulated at 3 GHz The pulses are measured by autocorrelation using SHG in LiIO3 They are the shortest pulses ever reported for a cw laser diode
227 citations
TL;DR: A system utilizing the Doppler shift of monochromatic laser light has been developed to measure blood flow in skin, and the heterodyned output signal is amplified and both RMS and dc values obtained.
Abstract: A system utilizing the Doppler shift of monochromatic laser light has been developed to measure blood flow in skin. Light from a low power (S mW) He-Ne laser is coupled into a quartz fiber and transmitted to the skin. This light is reflected from both the nonmoving tissues (reference beam) and moving red blood cells (Doppler shifted beam), received by a plastic fiber, and transmitted back to a photodiode where optical heterodyning occurs. The heterodyned output signal, which is proportional to the Doppler shift frequency, is amplified and both RMS and dc values obtained. The RMS value is weighted against the backscattered light intensity using the measured dc value as an index of total received power. This is used as the output flow velocity value.
227 citations
TL;DR: In this article, the Ideal Photon Detector and Coherent or Heterodyne Detection are discussed, as well as the effects of atmospheric turbulence on detector performance.
Abstract: 1. Thermal Radiation and Electromagnetic Modes.- 2. The Ideal Photon Detector.- 3. Coherent or Heterodyne Detection.- 4. Amplifier Noise and Its Effect on Detector Performance.- 5. Vacuum Photodetectors.- 6. Noise and Efficiency of Semiconductor Devices.- 7. Thermal Detection.- 8. Laser Preamplification.- 9. The Effects of Atmospheric Turbulence.- 10. Detection Statistics.- 11. Selected Applications.- References.
TL;DR: In this article, a 3.4mm-thick polycrystalline silicon was implanted with B to a dose of 5×1014/cm2 and irradiated in a cw laser scanning apparatus.
Abstract: 0.4‐μm‐thick polycrystalline silicon deposited in a low‐pressure CVD reactor was implanted with B to a dose of 5×1014/cm2 and then irradiated in a cw laser scanning apparatus. The laser annealing produced an increase in grain size from ∼500 A to long narrow crystals of the order of ∼25×2 μ, as observed by TEM. Each grain was found to be defect free and extended all the way to the underlying Si3N4. Electrical measurements show 100% doping activity with a Hall mobility of about 45 cm2/V sec, which is close to single‐crystal mobility at the same carrier concentration. Thermal annealing produces material with an average grain size of 1000 A and a resistivity higher by a factor of 2.2 than that obtained with the laser anneal. Laser annealing performed after a thermal anneal reduces the resistivity to approximately the same value obtained by laser annealing only.
TL;DR: In this paper, collision experiments using laser excited atoms in crossed beams are discussed, where the laser properties allow selecting the state into which the atom is excited, specific fine-and hyperfine-structure states may be chosen as well as a particular combination of sub-states.
Abstract: Publisher Summary This chapter discusses collision experiments using laser excited atoms in crossed beams. With the advent of tunable narrow-band lasers, especially cw dye lasers, the situation has changed and it has become clear that it should be possible to excite atoms optically within the scattering region of an otherwise conventional crossed-beam experiment. In this way a steady-state upper-state population could be reached that may be comparable to the ground-state population. When an atomic beam is excited, it is free of internal collisions and, for right angle intersection with the laser, free of Doppler broadening. Then the laser properties allow selecting the state into which the atom is excited. Specific fine- and hyperfine-structure states may be chosen as well as a particular combination of sub-states. The novel techniques allow preparing states with an angular momentum different from zero and to vary systematically the alignment and orientation of the resulting non-spherical interaction potentials. Frequency doubling of dye lasers can also widen the scale of possible applications. Very high powers are needed and one probably would have to use a pulsed laser. An alternative to frequency doubling is the direct two-photon excitation of atoms.
TL;DR: An equivalence theorem is formulated that provides conditions under which planar sources of different states of spatial coherence will generate optical fields that have identical far-zone intensity distributions.
Abstract: An equivalence theorem is formulated that provides conditions under which planar sources of different states of spatial coherence will generate optical fields that have identical far-zone intensity distributions. As an example, a partially coherent source whose linear dimensions are large compared with the correlation length of the light across the source is described that will generate a field whose far-zone intensity distribution is identical with that of a Gaussian laser beam.
TL;DR: In this article, the properties of boron-implanted silicon annealed by high power Q-switched ruby laser radiation are compared with results obtained by conventional thermal annealing.
Abstract: The properties of boron‐implanted silicon annealed by high‐power Q‐switched ruby laser radiation are compared with results obtained by conventional thermal annealing. Laser annealing of the implanted layer results in significantly increased electrical activity, as compared to thermally annealed implanted silicon. This correlates well with transmission electron microscopy and ion‐channeling measurements which show a dramatic removal of displacement damage as a result of laser annealing. A substantial redistribution of the implanted boron concentration profile occurs after laser annealing which cannot be explained by thermal diffusion in the solid.
TL;DR: In this article, it was shown that certain partially coherent model sources whose intensity distribution and degree of coherence are both gaussian will generate the same far-field intensity distributions as a completely coherent laser source.
TL;DR: In this article, a new spherical model is proposed, where the transient heating caused by the laser impact, represented by the three-dimensional heat pole, corresponds to a Gaussian distribution of the excessive temperature in space, and thus to the TEM00 mode of the incident laser beam.
Abstract: The generation of laser‐induced stress waves in liquids by the vaporization process and the thermoelastic effect was studied experimentally. A high‐speed camera and special high‐sensitivity stress transducers with a response time of a few nanoseconds have been used for these investigations. The experimental results obtained for water, n‐heptane, and carbon tetrachloride are discussed. For the first time, the individual contributions of vaporization and the thermoelastic effect on stress generation are separated. In addition, tunable high‐frequency acoustic waves, with frequencies up to 60 MHz, have been generated in water by the impact of a laser pulse exhibiting longitudinal mode beating. Since existing theories on the thermoelastic generation of acoustic waves do not yield satisfactory agreement with our experimental data, a new spherical model is proposed, where the transient heating caused by the laser impact, is represented by the three‐dimensional heat pole. This solution of the equation of heat conduction corresponds to a Gaussian distribution of the excessive temperature in space, and thus to the TEM00 mode of the incident laser beam. An analytical solution of the thermoelastic pressure wave is derived for this case of temperature distribution. Its good agreement with the experiment is discussed for various liquids and for two different laser characteristics.
Book•
01 Jan 1978
TL;DR: In this article, an extensive in-depth examination of gas kinetics, excitation processes, hydrodynamics, and other important aspects of gas lasers with specialization to CO2 is presented.
Abstract: The book offers an extensive in-depth examination of gas kinetics, excitation processes, hydrodynamics, and other important aspects of gas lasers with specialization to CO2. Almost every area of modeling discussed includes a standard description of an appropriate computer program. Most of the theory discussed is readily applicable to other gas systems. The discussion covers relaxation phenomena in gases, vibrational kinetics, electron excitation rates, rotational kinetics, a general plasma model, plasma chemistry models of gas lasers, stability analysis of laser plasmas, the Haas approximation to the general model, devices (unstable optical resonators, waveguide lasers, FIR gas lasers), and injection locking.
TL;DR: In this article, optical probe measurements of excited Ce3+ ions in Y3Al5O12 show that stimulated emission in the 550-610nm region is not possible at 295 K because of excited state absorption.
Abstract: Broad bandwidth 5d→4f transitions in Ce3+ have been considered for tunable laser action. In this letter, optical probe measurements of excited Ce3+ ions in Y3Al5O12 show that stimulated emission in the 550–610‐nm region is not possible at 295 K because of excited‐state absorption. Transient measurements demonstrate that part of this loss has ≈75‐ns lifetime and is associated with absorption from the lowest 5d level; a longer‐lifetime loss is also observed. The excited‐state‐absorption loss is reduced at lower temperatures.
TL;DR: New optical combinations of axicons and axicons with spherical mirrors and lenses suitable for laser machining are presented and potential new laser applications are discussed in relation to these optical devices.
Abstract: New optical combinations of axicons and axicons with spherical mirrors and lenses suitable for laser machining are presented. Linear and annular focusing, coaxially and radially to the laser beam, are possible. Most combinations allow continuous adjustment of exit beam parameters, focal line length, focal ring diameter, and magnification, by varying the relative position of one of the axicons. Potential new laser applications are also discussed in relation to these optical devices.
TL;DR: In this article, the authors used trapped ion cyclotron resonance spectroscopy and a CW CO/sub 2/ laser for photoionization of diethyl ether at long trapping times and low pressures.
Abstract: Recent studies have suggested the possibility of effecting dissociation processes with relatively low power CW lasers (several watts) provided that a molecule can be irradiated under nearly collision-free conditions for times approaching 1 sec. The establishment of such conditions and the observation of multiphoton dissociation processes are reported. The methodology applies techniques involving trapped ion cyclotron resonance spectroscopy and a CW CO/sub 2/ laser. Typical experimental conditions and results are described for the irradiation of diethyl ether at long trapping times and low pressures. The processes occurring during the photoionization were determined. The dissociation rate has a linear relationship with irradiation time and no dependence on wavelength over the 925 to 1090 cm/sup -1/ tuning region of the laser. (JSR)
TL;DR: In this article, the use of a laser as a tool for annealing of ion implantation damage is described, and electrical measurements show that activity comparable to that of a 1000 °C 30min anneal can be obtained.
Abstract: The use of a laser as a tool for annealing of ion‐implantation damage is described. The principal results obtained are as follows: (1) electrical measurements show that activity comparable to that of a 1000 °C 30‐min anneal can be obtained; (2) TEM measurements show that complete recrystallization of the damaged layer occurs during the laser anneal; (3) impurity profiles obtained from SIMS measurments show that the dopant atoms remain in the LSS profile during annealing. Simple diodes were fabricated to examine the feasibility of the method for device fabrication.
TL;DR: In this paper, the triplet quantum yield oT by laser flash absorption spectroscopy was derived for the case of triplet triplet oT with laser intensity and actionometry of a laser pulse.
Abstract: — In the comparative method of determining the triplet quantum yield oT by laser flash absorption spectroscopy, general equations are established (1) for describing the dependence of oT with laser intensity and (2) for absolute actionometry of a laser pulse. Applications to specific examples are discussed.
TL;DR: In this paper, the authors demonstrate the unique capability of a repetitively pulsed laser to write a monocrystalline pattern in ion-implanted amorphous silicon layers.
Abstract: We demonstrate the unique capability of a repetitively pulsed laser to ’’write’’ a monocrystalline pattern in ion‐implanted amorphous silicon layers. Ion‐channeling data, from the samples scanned with a focused beam of a Q‐switched Nd : YAG laser, show a continuity of the single‐crystal layer produced with spatially overlapping laser pulses, at 60–80 MW cm−2. Scattering yields indicate very high substitutionality of the implanted ions and an interdependence between the laser power density and the depth redistribution of the implants. Finally, similar recrystallization was obtained with a CO2 laser at 10.6 μm.
TL;DR: In this article, the authors achieved room temperature (300°K) operation of Ga(1−x)AlxAs•GaAs double-heterostructure lasers with active layers of quantum-well dimensions ∼200 A thick.
Abstract: The achievement of room‐temperature (300 °K) operation of Ga(1−x)AlxAs‐GaAs double‐heterostructure lasers with active layers of quantum‐well dimensions ∼200 A thick is reported. These devices are grown by metalorganic chemical vapor deposition and exhibit pronounced effects in the spectral and lasing characteristics that are related to the small active region thickness and are the first such effects observed for DH lasers in the GaAlAs‐GaAs system.
Journal Article•
TL;DR: Possibility to develop a "laser-scanning-microscope" on the basis of available techniques (laser microirradiation, miniprocessors, light detecting systems, automatic focusing, holographic focusing etc.) are discussed.
Abstract: In conventional light microscopy, the depth of focus is severely limited. This limitation might be overcome by a light optical scanning procedure. In this procedure, the specimen surface is scanned point for point by a focused laser beam. The image of the specimen surface is generated by an electronic system, similar to the procedure used in the scanning electron microscope. Possibilities to develop a "laser-scanning-microscope" on the basis of available techniques (laser microirradiation, miniprocessors, light detecting systems, automatic focusing, holographic focusing etc.) are discussed. On account of its possibility to form images of high resolution and depth of focus, a laser-scanning-microscope might become a valuable tool in addition to conventional light microscopy and scanning electron microscopy.
TL;DR: In this paper, simple approximate expressions are derived which permit convenient evaluation of the laser parameters from output power measurements in cavities with variable coupling, and conversely, of the maximum available oscillator power from small-signal gain and absorption-loss measurements.
Abstract: The exact equations relating the CW output power to the parameters of a homogeneously broadened laser with distributed loss and its cavity are analytically intractable. In their place, simple approximate expressions are derived which permit convenient evaluation of the laser parameters from output power measurements in cavities with variable coupling, and conversely, of the maximum available oscillator power from small-signal gain and absorption-loss measurements. The approximate solutions have negligible error for lossy standing-wave lasers and are but slightly less accurate for lossy traveling-wave ring lasers.
TL;DR: The form factors for the atmospheric backscattering of laser light leaving the exit aperture of a lidar receiving telescope are calculated in the limiting cases of purely geometrical optics and pure TEM(00) laser emission taking axial aperture displacement as well as misalignment of the transmitter axis into account.
Abstract: The form factors for the atmospheric backscattering of laser light leaving the exit aperture of a lidar receiving telescope are calculated in the limiting cases of purely geometrical optics and pure TEM(00) laser emission taking axial aperture displacement as well as misalignment of the transmitter axis into account. Some numerical results are plotted, displaying the effects of variations of the telescope's field of view, laser beam divergence, and misalignment.
TL;DR: Relations for the fluorescence signal under two common excitation geometries are derived and uncertainty relations used to consider the benefits of high laser intenstiy.
Abstract: The method of saturated fluorescence for measuring species concentrations in flames is usually performed with laser beams that do not provide a constant intensity distribution across the focal volume. Because of the intensity distribution across the beam, the fluorescence signal does not depend on laser power or intensity in the same manner as for uniform illumination. This leads to anomolous apparent saturation intensities. In the following, the effect is considered for atomic fluorescence. Relations for the fluorescence signal under two common excitation geometries are derived and uncertainty relations used to consider the benefits of high laser intenstiy.
TL;DR: A mathematical model is presented for the calculation of the 3-D time-dependent temperature distribution in a biological tissue (slab) irradiated by a laser beam of rectangular or Gaussian profile, which takes into account the different thermooptical properties of the tissue.
Abstract: A mathematical model is presented for the calculation of the 3-D time-dependent temperature distribution in a biological tissue (slab) irradiated by a laser beam of rectangular or Gaussian profile, which takes into account the different thermooptical properties of the tissue. Detailed consideration is given to the phenomenon of redistributive internal scattering, which is of noticeable magnitude in the irradiation by the argon-ion and Nd:YAG lasers commonly used for tissue coagulation in medicine. Satisfactory agreement is found with temperature measurements performed with a thermocamera, and the CO(2) and Nd:YAG lasers are compared qualitatively and quantitatively.