Showing papers on "Ruby laser published in 1990"

Treatment of Tattoos by Q-Switched Ruby Laser: A Dose-Response Study

Abstract: Tattoo treatment with Q-switched ruby laser pulses (694 nm, 40 to 80 nanoseconds) was studied by clinical assessment and light and electron microscopy. Fifty-seven blue-black tattoos or portions thereof (35 amateur and 22 professional) were irradiated with 1.5 to 8.0 J/cm2 at a mean interval of 3 weeks. Substantial lightening or total clearing occurred in 18 (78%) of 23 amateur tattoos and 3 (23%) of 13 professional tattoos in which the protocol was completed. Response was related to exposure dose. Scarring occurred in one case, and persistent confettilike hypopigmentation was frequent. Optimal fluence was 4 to 8 J/cm2. Clinicohistologic correlation was poor. Q-switched ruby laser pulses can provide an effective treatment for tattoos.

Characterization of pulsed laser deposited boron nitride thin films on InP

Abstract: A new technique for deposition of thin‐film boron nitride (BN) from BN wafers has been demonstrated using a Q‐switched ruby laser The deposition rate was found to be∼7 A/pulse at an energy density of 25 J cm−2 X‐ray photoelectron spectroscopy was used to confirm the film composition Infrared absorption peaks were observed at 802, 1370, and 1614 cm−1 characteristic of B—N bonds The films were found to have an indirect band gap of 41 eV with resistivity in excess of 1011 Ω cm and breakdown fields between 30×105—10×106 V cm−1 The dielectric constant of the films was in the range 319–328 The minimum interface state density on InP as obtained from C‐V (1 MHz) analysis was typically 62×1010 cm−2 eV−1, which increased to 41×1011 cm−2 eV−1 after annealing at 200 °C in argon Scanning electron microscopy studies showed that this resulted in the development of micropores in the film

Thin films of ferrite and ferroelectric materials deposited by pulsed laser vaporization process

Abstract: Thin films of BaTiO3 and Ni x Fe3−x O4 have been obtained by pulsed ruby laser evaporation process. In the case of BaTiO3 a sintered bulk pellet was used as the vaporization source, while Fe50Ni50 metallic alloy was used as the source for synthesis of nickel ferrite. The dependence of the film properties on oxygen partial pressure and laser energy density during deposition has been investigated. It is shown that thin films of these materials having good structural, morphological and stoichiometric properties can be obtained by the laser process by appropriate control of process parameters.

Double Line Stimulated Raman Scattering in Benzene

Abstract: Simultaneous stimulated Raman scattering at the 992 cm−1 and the 3063 cm−1 line of benzene is observed by mode-locked ruby laser pulse excitation. The double line stimulated Raman scattering is initiated by self-focusing. The influence of small-scale self-focusing, self-phase modulation, and cross-phase modulation on the double line stimulated Raman scattering is discussed. At low pump pulse intensities, before the onset of small-scale self-focusing, the steady-state Raman gain factors of both Raman lines are determined by Raman energy conversion efficiency measurements.

Laser pulse stretching via enhanced closed loop control with slow Q-switching

Abstract: A pulse stretching technique in a Q-switched ruby laser oscillator is described. The major improvement to our previously developed pulse stretching circuit consists in a more adequate waveform for the feedforward part. This new system gives fairly flat pulses with adjustable duration up to ∼ 100 μs and good coherence length in excess of 11 m. The cavity is followed by several amplifiers and produces light energies up to 8 J for holographic recording of particle tracks in the Fermilab 15-foot bubble chamber. The considerably increased coherence length will find applications in many fields of pulsed holography and its use with fiber optics is particularily promising.

Surface States of Laser-Irradiated Cadmium- and Tellurium-Containing Solid Solutions of II-VI Compounds

Abstract: Equilibrium conductivity and photoconductivity (PC) of MgxCd1−xTe (T = 300 K) and the PC and photomagnetic effect (PME) of CdxHg1−xTe (T = 77 K) solid solutions (SS) before and after irradiation with ruby laser pulses in the Q-switched mode are analyzed. Laser irradiation is shown to increase the forbidden gap width and to change the stoichiometric composition in the subsurface region of the SS. In n-type MgxCd1−xTe crystals a donor-enriched layer is formed and a Te film appears on the surface; in n-type CdxHg1−xTe crystals a conductivity-type inversion occurs and a built-in p–n junction arises under the action of laser emission pulses. [Russian Text Ignored].

Tin diffusion and segregation in GaAs processed with a pulsed ruby laser

Abstract: Tin‐diffused GaAs layer samples, with mean concentrations larger than 1019 cm−3, were obtained by irradiating with a ruby laser GaAs substrates covered with thin tin layers. Mobilities between 100 and 200 cm2/V s were obtained. Both carrier concentration and mobility decrease with increasing energy density. Strong segregation effects were observed in the samples processed with large energy densities.

Monitoring of a high-power pulsed ruby laser

Abstract: A high-power pulsed ruby laser was used to take holograms of neutrino interactions in the Fermilab 15-foot Bubble Chamber. This paper describes a system to monitor and record its most relevant parameters such as the light pulse energy, its width and shape, and the spatial intensity distribution. A second aim of this system was to help in the alignment of the laser beam towards the dispersing lens, located inside the Bubble chamber, as well as to provide a fast check of the alignment without interrupting the holographic recording. This system was required to work in the strong magnetic field (∼0.5 T ) surrounding the 15-foot Bubble Chamber, which introduced additional technical problems.

Stress‐released layer formed by pulsed ruby laser annealing on GaAs‐on‐Si

Abstract: The effects of short pulsed ruby laser annealing on GaAs layers grown on Si substrates by metalorganic chemical vapor deposition have been characterized by Raman spectroscopy and double‐crystal x‐ray diffraction. After laser melting and regrowth, the stress‐released layer is formed in the near‐surface. The formation of the stress‐released layer results in the microcracking of the pulsed‐laser‐annealed GaAs surface. However, the high crystalline quality of this stress‐released layer is detected. Furthermore, when GaAs layer is overgrown on this stress‐released layer, this layer plays a role of blocking the dislocation threading into the overgrown GaAs layer.

Laser‐produced plasma with large amplitude density modulation of controllable wavelength

Abstract: A 6 nsec 1010 W/cm2 ruby laser pulse irradiates a grating with spacing in the 6–35 μm range. The expansion of the plasma above the surface is observed using interferometry and shadowgraphy. The plasma is found to be modulated with n/n up to 8%. Such a plasma can be used to accelerate charged particles.

Use of the HeCd and argon laser to cure dental composites when compared with white light sources

Abstract: Since the development of the ruby laser in the early 1960's there has been interest in the area of lasers in dentistry. This interest centered around both hard and soft tissue applications. In the 1970's dentists began using an ultra-violet (UV) light source in the photopolymerization of composite dental materials. Because of the concern regarding the UV light in the mouth a composite resin which activated at 460 nm light was developed. It is intriguing to consider the laser as a better curing light by virtue of the fact that this light is monochromatic, coherent and well collumated. The question this paper has attempted to answer is whether or not laser energy is of benefit in the curing of dental composite resins. A Helium Cadmium (442nm) and Argon Laser (488 nm) were used and compared with a typical dental white light curing unit. Both micro and small particle-sized composites were examined. The results suggest that the lasers tested are not of any great benefit over conventional methods.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multiframe high-speed laser schlieren system for observations of prebreakdown phenomena in liquids in nanosecond region

Abstract: A six-frame high-speed laser schlieren system which has variable intervals from frame to frame has been developed. A ruby laser with a pulse duration of 5 ns is used as the light source. By means of this system, one can obtain a sequence of six schlieren pictures of an electrical discharge with one shot of the main laser. A time delay between two diagnostic pulses is 5-50 ns and can easily be changed. The applicability of the system is demonstrated for rapidly changing prebreakdown processes in liquid dielectrics in the nanosecond region. >

Propagation of laser-generated acoustic pulses in agr graphite

Abstract: Laser-based systems for non-contact generation and detection of ultrasound are being investigated at the CEGB's Marchwood Engineering Laboratories for application to remote non-destructive inspection problems. These include the in-situ inspection of the graphite bricks that make up the cores of Advanced Gas-Cooled Reactors (AGR's). The propagation of laser-generated ultrasonic pulses in AGR graphite has been studied using a laboratory system incorporating a Q-switched ruby laser generator and Michelson interferometer detector

Real-time diffraction gratings in DDI-methanol solutions

Abstract: Nondegenerate four-wave mixing has been performed in DDI-methanol solutions using ruby laser as writing beams. The reading beam was either a pulsed one at 538.8 nm or a continuous one at 632.8 nm. Contributions from both saturation and thermal gratings were separated temporally and evaluated.

Pulsed laser treatment of Fe2O3 film on Al2O3

Abstract: Fe2O3 film (∼110 A) on crystalline Al2O3 substrate is treated by ruby laser pulses at different energy densities up to a maximum of ∼75 J/cm2, and the transformations are examined by conversion electron Mossbauer spectroscopy and small‐angle x‐ray diffraction measurements It is observed that transformations begin to appear in the sample at an energy density of ∼30 J/cm2 although significant modifications are observed only at energy densities higher than about 70 J/cm2 The values of hyperfine interaction parameters reveal that the laser treated samples contain FeAlO3 and FeAl2O4 phases, along with the residual α‐Fe2O3 phase The laser‐mixed state undergoes structural modifications upon thermal annealing, leading to formation of the Fe3O4 phase and complete disappearance of the FeAlO3 phase

Laser annealing of phosphorus-implanted CdTe

Abstract: Single crystals of p-CdTe were implanted with phosphorus ions (100 keV, fluence of 10 14 ions cm −2 ). Pulsed ruby laser annealing was carried out at energy densities of 1.9–3.2 J cm −2 and compared with thermal annealing for 1 h at 300°C. Resistivity measurements showed that laser annealing produced significantly lower resistivity than thermal annealing, the lowest resistivity of 1.95 Ω cm being obtained at 1.9 J cm −2 . Scanning electron micrographs showed better morphology with laser annealing.

Demonstration of optical phase conjugation by stimulated Brillouin scattering using a gas lens

Abstract: A gas lens is used to focus ruby laser light into a cell containing carbon disulphide, thus causing stimulated Brillouin scattering to occur. The reflected light is switched out of the system and focused using a 10 cm focal length lens. The focal spot is imaged with a calibrated TV camera. The beam quality is comparable with that achieved with an equivalent focal length glass lens placed before the cell. The phase conjugate nature of the reflected light is demonstrated by replacing the SBS cell with a dielectric mirror and noting the significant distortion. The reflectivity of the SBS cell using the gas and the glass lenses is measured at different input powers.

Solid state lasers for reproduced picosecond and femtosecond light pulses

Abstract: The passive mode-locking of solid-state lasers in the stable regime of a stationary single pulse is investigated from the point of view of designing reliable sources of picosecond, subpicosecond, and femtosecond light pulses. The direction of the transient evolution and steady regime of laser generation is determined from the Liapunov functional, and the self-phase modulation of ultrashort pulses and the shortest pulse duration are discussed. The output power, spectrum, and transient evolution of the spectral shape of mode-locked pulses of a ruby laser and Nd:glass laser are analyzed, and it is shown that pulse widths are in good agreement with the theoretical predictions.

Laser ablation for direct elemental analysis of solid samples by ICP-atomic emission spectrometry and ICP-mass spectrometry

Abstract: ICP-AES and ICP-MS methods have been developed for the direct analyses of solid metals and nonconductive powder samples. A ruby laser was used for ablating solid samples, and aerosols produced were directly introduced into the inductively coupled plasma by the flow of Ar carrier gas. The recommended procedure has been applied to steels, silicate rocks and slags. In this paper, the results of a preliminary study on the laser ablation technique are described with the applications for the analyses of these samples

The History and Development of the Medical Laser

Abstract: Laser medicine can be divided into two areas, laser surgery and laser medicine [1]. The area of laser cardiovascular research and development encompasses both of these disciplines. This review will emphasize the development and progress of those phases concerned with nonsurgical applications.

Optisches filter fuer laserstrahlen und verfahren zu seiner herstellung

Abstract: An optical filter for absorbing neodymium YAG-doubled laser radiation at 532 nanometers, comprises a polymeric transparent matrix e.g. polycarbonate, containing platinum deuteroporphyrin IX dimethyl ester shown, and has an optical density of 1.8 at 532 nm while having a photopic luminous visible transmission of 53.8%. Optionally, the fitter may contain other additives for absorption at other laser wavelengths, such as vanadyl tetra-4-tert-butylphthalocyanine for absorption of ruby laser radiation at 694 nanometers and tris (p- diethylaminophenyl) aminium hexafluoroantimonate for absorption of neodymium YAG laser radiation at 1064 nanometers.

High-energy Q-switched Single Longitudinal Mode Operation from Solid-state Ring Lasers

Abstract: In this paper 30 mJ SLM operation is reported from flashlamp-pumped Nd:YAG and Ruby ring resonators. Unidirectional operation was obtained through use of a 45° Faraday rotator and 45° quartz rotator. With the use of broad free spectral range (FSR) and narrow FSR intracavity etalons reliable SLM operation was achieved without precise control of resonator length. The modal purity was better than 1000:1 on 99% of shots in the case of the ruby laser and 200:1 on 99% of shots for the Nd:YAG laser. The timing jitter of the SLM pulse was typically less than ± 5 ns.

Historical Background, Development, and Future Trends of Lasers in Cardiovascular Disease

Abstract: The acronym laser stands for light amplification by stimulated emission of radiation. The principle of laser theory was first described by Albert Einstein in 1917 [1]. It was not until 1958 that Townes and Schawlow in the United States and Prokhorov in the Soviet Union further expanded on laser theory, which eventually led to the construction of the first laser in I960. This was a solid-state ruby laser built by Theodore Maiman at the Hughes Laboratories [2].

High-power ruby and alexandrite lasers for LIDAR-Thomson scattering diagnostics

Abstract: By combining the time-of-flight or LIDAR principle with a Thomson backscatter diagnostic, spatial profiles of the electron temperature and density can be measured with a single set of detectors for all spatial points. The technique was demonstrated for the first time on the JET tokamak and has been in routine operation since July 1987. Originally a ruby laser (3 J pulse energy, 300 Ps pulse duration, 0.5 Hz repetition rate) was used together with a 700 MHz bandwidth detection and registration system which yielded a spatial resolution of about 12 cm. A large filter spectrometer with 6 spectral channels covering the wavelength range 400 - 800 nm gives a dynamic range for the temperature measurements of 0.2-20 keV. The original system is described, examples of measurements are given and compared with the results of other diagnostics. The system is being upgraded to make measurements at 10 Hz and a major component of the new system is an Alexandrite laser (1-2 J pulse energy, 350+1-50 ps pulse duration, 10 Hz repetition rate) which is currently being constructed. The new laser and other technological improvements being incorporated into the upgraded diagnostic will also be described.

Ruby laser: a superior method for removing tattoos

Abstract: Tattoos are physically painful to receive, socially painful to bear, and until now have been painful to remove. The processes used to remove tattoos are an unpleasant catalogue of destructive techniques that produce far less than acceptable cosmetic results.

Therapeutic Application of Milliwatt Level He-Ne Laser for Vasculogenic Red Lesions

Abstract: Therapeutic application of lasers for abnormal colored lesions is one of the most miraculous application of lasers in medicine and has reached the practical stage, taking place of the conventional treatment owing to the clinical advantages and the simplicity of its therapeutic technique. The greatest advantage in this laser treatment is that the anomaly of color only in the abnormal colored lesion can be improved to the normal color, depending on the interaction of their optical characteristics and the wavelength of the lasers. This therapy has thus emerged as one of the most useful clinical applications of lasers. In the laser treatment to remove colored lesions, comparatively high powered lasers such as the argon or the ruby laser have usually been applied1). In addition to this, the authors2) have found the useful therapeutic effect that a low power He-Ne laser of milli-watt level output power can be effectively applied to the treatment of vasculogenic red lesions such as subcutaneous hemorrhage, capillary disorder and hemangioma.

Laser surface-melting of metals studied by PAC

Abstract: High purity Pt, Ni, Cu, Fe and Al metal foils were electroplated with carrier-free111In probe atoms and melted at 293 K using 32 ns ruby laser pulses with energy densities in the range 1–10 J cm−2. Three distinct lattice locations of the probe atoms were detected in the melted surface layers using perturbed γ-γ angular correlation spectroscopy: (i) defect-free substitutional sites, (ii) non-unique sites with broad distributions of quadrupole interactions, and (iii) a probemonovacancy complex (for Pt only). The defect-free fraction was found to approach 100% when Pt is irradiated at 9 J cm−2. The fraction of probes on defect-free sites was found to increase with the energy density of the pulse and with the solubility of In in the metals. The data are consistent with the idea that laser surface-melting produces high concentrations of vacancies and lattice sinks, although no thermal trapping of point defects was detected.