Showing papers on "Laser published in 1983"

Laser phase and frequency stabilization using an optical resonator

Abstract: We describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer. High sensitivity for detection of resonance information is achieved by optical heterodyne detection with sidebands produced by rf phase modulation. Physical, optical, and electronic aspects of this discriminator/laser frequency stabilization system are considered in detail. We show that a high-speed domain exists in which the system responds to the phase (rather than frequency) change of the laser; thus with suitable design the servo loop bandwidth is not limited by the cavity response time. We report diagnostic experiments in which a dye laser and gas laser were independently locked to one stable cavity. Because of the precautions employed, the observed sub-100 Hz beat line width shows that the lasers were this stable. Applications of this system of laser stabilization include precision laser spectroscopy and interferometric gravity-wave detectors.

Computed radiography utilizing scanning laser stimulated luminescence

Abstract: A new system of computed radiography that is based on new concepts and the latest computer technologies has been developed. This system eliminates the drawbacks of conventional screen-film radiography. The basic principle of the system is the conversion of the x-ray energy pattern into digital signals utilizing scanning laser stimulated luminescence (SLSL).

Degenerate four-wave mixing in semiconductor-doped glasses

Abstract: We report degenerate four-wave mixing (DFWM) of visible radiation in borosilicate glasses doped with crystallites of the mixed semiconductor CdSxSe1−x. These semiconductor-doped glasses—available commercially in the form of colored glass filters—exhibit third-order nonlinearities of ~10−9–10−8 esu for DFWM with short (~10-nsec) laser pulses at various visible wavelengths. Our studies on the temporal decay of the transient gratings indicate that the nonlinearity is not thermal in origin but may be attributed to the generation of a short-lived electron–hole plasma. In contrast with DFWM experiments in other semiconductors invoking gratings of optically generated carriers (or other mobile particles), we report unique diffusion-independent decay of the gratings in these glasses; this is deduced from the dependence of the intensity and polarization of the DFWM signal on the polarization combinations of the input beams. Finally, we report detailed data on the aberration-correction properties of these isotropic glasses.

Time-resolved laser-induced breakdown spectrometry of aerosols

Abstract: The repetitive breakdown spark from a focused laser beam was used to generate analytically useful emission spectra of aerosols in air. The apparatus is simple; a pulsed laser and optics, a spectrometer, and some method for time resolution of the spark light. Time resolution is essential because of the strong continuum emission at early times (<500 ns). High temperatures in the spark result in vaporization of small particles, dissociation of molecules, and excitation of atomic and ionic spectra. The plasma acts as if it were in local thermodynamic equilibrium, at least after 1 ..mu..s. Spectroscopic methods have been used to measure the time-resolved temperatures and electron densities. A simple one-dimensional hydrodynamic model predicts the temperature and diameter of the spark. Beryllium in atmospheric pressure air has been detected at 0.7 ..mu..g/m/sup 3/, which is 0.6 ng/g of air (RSD = 30%). Limits of detection have also been established for Na, P, As, and Hg in air. A calibration curve linear over 4 orders of magnitude has been developed for Na in air. In situ experiments have been performed on two experimental coal gasification systems, and real-time spectral information has been obtained in both cases. 37 references, 9 figures, 2 tables.

Optical bistability and mirror confinement induced by radiation pressure

Abstract: This paper reports the observation of optical bistability due to a radiation-pressure-induced change of the length of a Fabry-Perot resonator. In addition, for higher laser powers, a purely optical mechanism leading to the stabilization of the resonator has been observed.

Principles of lasers

Abstract: Manuscript received April 14, 1983; revised June 24, 1983. N. B. Abraham is with the Department of Physics, BrynMawr College, Bryn Mawr, PA 19010. P. Mandel is with the Service de Chimie Physique 11, Universite Libre de Bruselles, Brussels, Belgium. L. W. Casperson is with the Department of Electrical Engineering and Applied Science: University of California, Los Angeles, CA 90024. Editor’s Note: A similar correction by Dr. F. Holigner and Prof. Dr. H. Weber of the Universitat Kaiserslautern was received on May 4, 1983. tions can be expressed as BR = y + p P (3a j

Direct etching of polymeric materials using a XeCl laser

Abstract: The direct etching of polyethylene terephthalate film using a XeCl laser has been investigated and is shown to be consistent with a thermal model for degradation. Microstructure revealed by deep etching suggests the UV laser may prove useful for studying polymeric materials. Polyimide and photoresist film has also been directly etched.

Microwave signal generation with injection-locked laser diodes

Abstract: Heterodyne detection of the light from two slave lasers injection locked to FM sidebands of a modulated master laser is used to generate a narrowband microwave signal at 10.5 GHz.

Laser processing and analysis of materials

Abstract: 1 Lasers and Laser Radiation.- 1.1. Introduction.- 1.2. Laser Sources.- 1.2.1. Ruby Laser.- 1.2.2. Nd-YAG Laser.- 1.2.3. Nd-Glass Laser.- 1.2.4. Tunable Infrared Diode Lasers.- 1.2.5. Helium-Neon Laser.- 1.2.6. Argon and Krypton Ion Lasers.- 1.2.7. Helium-Cadmium Laser.- 1.2.8. CO2 Laser.- 1.2.9. Rare Gas Halide Lasers.- 1.2.10. Dye Lasers.- 1.2.11. Stimulated Raman Scattering.- 1.3. Laser Radiation.- 1.3.1. Monochromaticity.- 1.3.2. Beam Shape.- 1.3.3. Beam Divergence.- 1.3.4. Brightness.- 1.3.5. Focusing of Laser Radiation.- 1.3.6. Coherence.- 1.4. Lens Aberrations.- 1.4.1. Spherical Aberration.- 1.4.2. Coma.- 1.4.3. Astigmatism.- 1.4.4. Field Curvature.- 1.4.5. Distortion.- 1.5. Window Materials.- 1.6. Mirrors and Polarizers.- 1.7. Q-Switching.- 1.7.1. Acousto-Optical Q-Switches.- 1.7.2. Electro-Optical Q-Switches.- 1.7.3. Passive Q-Switching.- 1.8. Frequency Conversion.- 1.9. Mode Locking.- 1.10. Detectors and Power Meters.- 1.10.1. Power Meters.- 1.10.2. Radiation Detectors.- 2. Materials Processing.- 2.1. Absorption of Laser Radiation by Metals.- 2.2. Absorption of Laser Radiation by Semiconductors and Insulators.- 2.3. Thermal Constants.- 2.4. Laser Drilling: Heat Transfer.- 2.4.1. Heating without Change of Phase.- 2.4.2. Heating with Change of Phase.- 2.4.3. Experimental.- 2.5. Welding.- 2.5.1. Heat Transfer-Penetration Welding.- 2.5.2. Heat Transfer-Conduction Welding.- 2.5.3. Welding with Multikilowatt Lasers.- 2.5.4. Welding with Low-Power Lasers.- 2.5.5. Laser Spot Welding.- 2.6. Cutting.- 2.6.1. Heat Transfer.- 2.6.2. Cutting Metals.- 2.6.3. Cutting Nonmetals.- 2.6.4. Scribing and Controlled Fracture.- 2.7. Micromachining.- 2.7.1. Resistor Trimming.- 2.7.2. Machining of Conductor Patterns.- 2.7.3. Fabrication of Gap Capacitors.- 2.7.4. Image Recording.- 2.7.5. Laser Marking.- 2.7.6. Micromachining-Thermal Considerations.- 2.8. Surface Hardening.- 2.9. Surface Melting, Alloying, and Cladding.- 2.10. Surface Cleaning.- 2.11. Crystal Growth.- 2.12. Optical Fiber Splicing.- 2.12.1. Optical Fiber-End Preparation.- 2.12.2. Optical Fiber-Drawing.- 2.13. Laser Deposition of Thin Films.- 2.13.1. Evaporation.- 2.13.2. Electroplating.- 2.13.3. Chemical Vapor Deposition.- 2.13.4. Photodeposition and Photoetching.- 3 Laser Processing of Semiconductors.- 3.1. Introduction.- 3.2. Annealing.- 3.3. Annealing-CW Lasers.- 3.4. Recrystallization.- 3.5. Silicide Formation.- 3.6. Ohmic Contacts and Junction Formation.- 3.7. Device Fabrication.- 3.8. Electrical Connections on Integrated Circuits.- 3.9. Monolithic Displays.- 4 Chemical Processing.- 4.1. Introduction.- 4.2. Schemes for Laser Isotope Separation.- 4.3. The Enrichment Factor.- 4.4. Laser-Induced Reaction.- 4.5. Single-Photon Predissociation.- 4.6. Two-Photon Dissociation.- 4.7. Photoisomerization.- 4.8. Two-Step Photoionization.- 4.9. Photodeflection.- 4.10. Multiphoton Dissociation.- 4.10.1. Deuterium.- 4.10.2. Boron.- 4.10.3. Carbon.- 4.10.4. Silicon.- 4.10.5. Sulfur.- 4.10.6. Chlorine.- 4.10.7. Molybdenum.- 4.10.8. Osmium.- 4.10.9. Uranium.- 4.11. Selective Raman Excitation.- 4.12. Economics of Laser Isotope Separation.- 4.13. Laser-Induced Reactions.- 4.13.1. Infrared Photochemistry-Basic Mechanisms.- 4.13.2. Vibrationally Enhanced Chemical Reactions.- 4.13.3. Vibrationally Induced Decomposition.- 4.14. Isomerization.- 4.15. Lasers in Catalysis.- 4.16. Laser-Induced Reactions: UV-VIS Excitation.- 4.17. Processing via Thermal Heating.- 4.18. Polymerization.- 5 Lasers in Chemical Analysis.- 5.1. Introduction.- 5.2. Absorption Spectroscopy.- 5.2.1. Absorption vs. Other Techniques.- 5.2.2. Intracavity Absorption.- 5.3. Laser-Induced Fluorescence.- 5.3.1. Laser-Induced Fluorescence: Theory.- 5.3.2. Laser-Excited Atomic Flame Fluorescence.- 5.3.3. Laser-Excited Molecular Flame Fluorescence.- 5.3.4. Beam Diagnostics.- 5.3.5. Fluorimetry and Phosphorimetry.- 5.3.6. Selective Excitation of Probe Ion Luminescence.- 5.4. Laser-Enhanced Ionization Spectroscopy.- 5.5. Multiphoton Ionization.- 5.6. Raman Spectroscopy.- 5.6.1. Theory and Physical Principles.- 5.6.2. Experimental Techniques.- 5.6.3. Experimental Results.- 5.6.4. Coherent Anti-Stokes Raman Spectroscopy.- 5.7. Laser Magnetic Resonance.- 5.8. Laser Photoacoustic Spectroscopy.- 5.8.1. LPS of Gases.- 5.8.2. LPS of Liquids and Solids.- 5.8.3. Photoacoustic Imaging.- 5.9. Laser Microprobe.- 5.10. Atomic Absorption Spectrometry.- 5.11. Laser Microprobe Mass Spectrometer.- 5.12. Laser Raman Microprobe.- 5.13. Lasers in Chromatography.- 6 Lasers in Environmental Analysis.- 6.1. Propagation of Laser Radiation through the Atmosphere.- 6.2. Laser Remote Sensing of the Atmosphere.- 6.2.1. Absorption Measurements.- 6.2.2. LIDAR.- 6.2.3. Laser Remote Sensing of Wind Velocity.- 6.2.4. Raman LIDAR.- 6.2.5. Differential Absorption LIDAR (DIAL).- 6.2.6. Resonance Fluorescence.- 6.2.7. Heterodyne Detection.- 6.3. Laser Sampling of Aerosols.- 6.3.1. Particle Size and Distribution.- 6.3.2. Particle Composition.- 6.3.3. Interaction of High-Power Laser Radiation with Aerosol Particles.- 6.4. Laser Remote Sensing of Water Quality.- References.- Materials Index.

10 kHz linewidth 1.5 μm InGaAsP external cavity laser with 55 nm tuning range

Abstract: An InGaAsP 1.5 μm laser, with one facet antireflection coated, has been incorporated into a diffraction grating external cavity. The lasing wavelength could be tuned over a 55 nm range about the centre wavelength of 1.5 μm by rotating the grating. Furthermore, it was found that the emission spectrum was extremely narrow; beat-frequency measurements at 1523 nm against an HeNe laser showed it to be of the order of 10 kHz.

Optoelectronics, an introduction

Abstract: 1. Light. 2. Elements of Solid-State Physics. 3. Modulation of Light. 4. Display Devices 5. Lasers 1. 6. Lasers 2 7. Photodetectors. 8. Fibre Optical Waveguides. 9. Optical Communication Systems. 10 .Noncommunication Application of FIbres.

High‐speed direct single‐frequency modulation with large tuning rate and frequency excursion in cleaved‐coupled‐cavity semiconductor lasers

Abstract: We report a new mechanism of direct frequency modulation, the cavity‐mode enhanced frequency modulation (CME‐FM), using the newly developed cleaved‐coupled‐cavity (C3) semiconductor laser. In this operation, one of the diode of the C3 laser was operated as a laser, while the other diode was operated as a frequency modulator. It was shown that a very large frequency excursion of 150 A and frequency tuning rate of 10 A/mA have been obtained with a C3 GaInAsP crescent laser operating at 1.3 μm. Time‐resolved spectral and spectral‐resolved pulse response measurements also showed that such C3 lasers operated in highly stable single‐longitudinal mode at all times even under high‐speed direct frequency modulation. In addition to the important application as the optical source in FM optical communication systems, the present CME‐FM C3 laser can also be used as the optical source in wavelength‐division multiplexing systems. Further, it opens the possibility of ultrahigh capacity multilevel optical FM information t...

Use of induced spatial incoherence for uniform illumination on laser fusion targets. Memorandum report

Abstract: We report a technique to achieve very uniform illumination of laser irradiated targets by inducing a controlled amount of transverse spatial incoherence in the output beam of a broadband laser. The spatial incoherence is created by imposing different optical delays upon different transverse sections of the beam, and choosing the delay increments to be larger than the laser coherence time tc = 1 delta. This technique may allow easy attainment of the pellet illumination uniformity required for laser fusion.

Semiclassical theory of noise in semiconductor lasers - Part II

Abstract: A model of semiconductor laser noise is presented which includes the carrier density as a dynamical variable and the carrier density dependence of the refractive index. The Van der Pol laser noise model is shown to he a special case of this treatment. Expressions are calculated for all laser spectra and compared with their Van der Pol counterparts. The power fluctuations spectrum and the frequency fluctuations spectrum exhibit a resonance corresponding to the relaxation resonance and the field spectrum contains fine structure, similar to sidebands which result from harmonic frequency modulation of a carrier signal. The role of carrier noise in determining the field spectrum linewidth is also considered.

Thermal-wave detection and thin-film thickness measurements with laser beam deflection

Abstract: A new technique has been developed that employs highly focused laser beams for both generating and detecting thermal waves in the megahertz frequency regime. This technique includes a comprehensive 3-D depth-profiling theoretical model; it has been used to measure the thickness of both transparent and opaque thin films with high spatial resolution. Thickness sensitivities of ±2% over the 500–25,000-A range have been obtained for Al and SiO2 films on Si substrates.

Measurement of the linewidth enhancement factor α of semiconductor lasers

Abstract: A theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented. In this model the amplitude modulation couples through the complex susceptibility of the gain medium to the phase. We show that this coupling constant can be obtained by a high‐frequency modulation experiment. This measured coupling constant is used to infer the linewidth enhancement factor α as discussed by Henry, and Vahala and Yariv. Experiments confirmed the model and we measured a linewidth enhancement factor ‖α‖=4.6±1.0 for a GaAlAs buried optical guide laser.

Circuit modeling of the effect of diffusion on damping in a narrow-stripe semiconductor laser

Abstract: This paper describes a circuit modeling technique for directly modulated narrow-stripe semiconductor lasers with strong carrier confinement and index guiding It is shown that diffusion damping of the modulation response, due to a nonuniform electron density distribution in the active layer, can be accounted for in terms of an equivalent optical gain saturation Based on this equivalence, a small-signal ac circuit model of a narrow-stripe laser is derived The model can be used to determine the intensity modulation and frequency modulation response characteristics of a packaged device

Subpicosecond electrical sampling

Abstract: We report on the recent advances of an electrooptic sampling technique for the characterization of electrical transients that has now achieved an unprecedented temporal resolution of less than 1 ps. Voltage sensitivity is on the order of 50 μV. A lithium tantalate traveling wave Pockels cell is employed in conjunction with a high repetition rate subpicosecond laser system.

Phase-locked (GaAl)As laser diode emitting 2.6 W CW from a single mirror

Abstract: A phase-locked multiple-quantum-well (GaAl)As injection laser with a highly reflective rear facet coating and a low reflective front facet coating is reported to emit 2.6 W CW at room temperature from the front facet.

Reshaping collimated laser beams with Gaussian profile to uniform profiles.

Abstract: A set of holographic filters was developed to convert the Gaussian intensity distribution of a collimated laser beam into a uniform one. The design and the fabricating method of the holographic filters are presented and experimental results are shown.

Investigation of trigonal (La1−xNdx)3Ga5SiO14 crystals. II. Spectral laser and electromechanical properties

Abstract: Absorption, luminescence characteristics, and stimulated emission parameters of Nd3+ ions in the wide temperature region of a full concentration series of (La1−xNdx)3Ga5SiO14 single crystals are studied. Luminescence intensity characteristics are analyzed and transition cross-section at the laser wavelengths of two 4F3/2 4I11/2 and 4F3/2 4I13/2 generation channels of activator are determined. Registered induced transitions are identified. Electromechanical characteristics of La3Ga5SiO14, specifically, elastic, dielectric, and piezoelectric modules and constants are investigated. A comparison of the properties between La3Ga5SiO14 crystals and crystalline SiO2 is carried out. [Russian Text Ignored.]

Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence.

Abstract: A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation at 514.5 nm. Measurements were made simultaneously at 10,000 points in an iodine-seeded supersonic flowfield with a 100 x 100 element photodiode array camera and were found to agree well with a numerical solution for the velocity field. The accuracy with which a component of velocity can be measured is limited, in the current approach, by the iodine linewidth to about +/-5 m/sec.