Showing papers on "Ruby laser published in 1993"

Clinical use of the Q-switched ruby and the Q-switched Nd:YAG (1064 nm and 532 nm) lasers for treatment of tattoos.

Abstract: background. The desire to remove tattoos has probably been around as long as their existence. Recent technological advances in lasers have finally made it possible to remove tattoos without leaving an equally undesirable scar. objective. The purpose of this article is to review the use of the Q-switched ruby (694 nm) and the Q-switched Nd:YAG (532 and 1064 nm) lasers for effective removal of tattoo ink, with cosmetically appealing results. results. The Q-switched ruby laser (694 nm) effectively removes blue-black and green ink, may treat other colors less efficiently, and is frequently associated with transient pigmentary changes, including rare depigmentation. The Q-switched Nd:YAG laser at 1064 nm quickly removes black ink, as well as other colors less efficiently; pigmentary changes are much less frequent, correlating with its lower absorption by melanin. The 532-nm wavelength treats red ink effectively, but also leads to temporary hypopigmentation. Transient textural changes may be noted at all three wavelengths discussed, but scarring is rare. conclusions. Q-switched lasers can remove tattoos without residual scarring. Efficacy of ink removal is dependent on the wavelength used for the targeted pigment.

Cosmetic Tattoo Ink Darkening: A Complication of Q-Switched and Pulsed-Laser Treatment

Abstract: Background: High-energy, short-pulse lasers, eg, Q-switched lasers, emitting visible and near-infrared light have recently been developed for removing tattoos, with little risk of scarring. The mechanisms of action, and possible adverse effects other than scarring and hypopigmentation, are not fully understood. Observations: We describe five cases of pulsed-laser— induced, immediate, irreversible darkening of cosmetic, white, flesh (skin-color), and pink-red colored tattoos. Irreversible ink darkening can be an insidious complication, because immediate whitening of the skin temporarily obscures the subsequently impressive color change. Among these cases, irreversible ink darkening occurred with Q-switched ruby (694 nm), Q-switched neodymium (Nd):YAG (1064 nm/532 nm), and pulsed green dye (510 nm) lasers. Attempts to remove the darkened ink with further laser treatment failed in two cases, and surgical excision was necessary. In the other three cases, subsequent laser treatments successfully removed the darkened ink. The red cosmetic tattoo ink used in one of the cases was placed in agar in vitro and was converted to a black compound immediately on Q-switched ruby laser exposure. Ferric oxide, a brown-red ingredient commonly used in cosmetic tattoos, was similarly tested and blackened in vitro by Q-switched ruby laser exposures. Conclusions: Although most tattoos are not darkened by laser treatment, short-pulsed lasers over a wide spectrum can cause immediate darkening of some tattoo inks. Patients should be warned of the potential for irreversible cosmetic tattoo darkening, and test-site exposures should be performed prior to treatment. In some cases, subsequent laser treatments may remove the blackened ink. The mechanism probably involves, at least for some tattoos, reduction of ferric oxide (Fe 2 O 3 , "rust") to ferrous oxide (FeO, jet black), but the chemical reaction that is involved remains unknown. ( Arch Dermatol. 1993;129:1010-1014)

Benign pigmented lesions of the skin. Treatment with the Q-switched ruby laser

Abstract: background. The Q-switched ruby laser is a 694 nanometer (red light) pulsed (20–40 nsecond) laser that has been shown to be effective in the treatment of cutaneous pigmented lesions. objective. This article will review my experience in the use of the Q-switched ruby laser to treat a wide gamut of epidermal and dermal pigmented lesions. results. The Q-switched ruby laser is highly effective in treating epidermal pigmented lesions and can be efficacious in the treatment of some dermal pigmented lesions. conclusion. The Q-switched ruby laser is an effective addition to the cutaneous laser armamentarium.

Rapid Response of Traumatic and Medical Tattoos to Treatment with the Q-switched Ruby Laser

Abstract: Traumatic tattoos can be very difficult to remove. Excision is often not possible because of the extent of the tattoo, and dermabrasion may not be able to reach the area of pigment without significant scarring. Six patients with traumatic (n = 5) or medical (n = 11) tattoos were treated with the Q-switched ruby laser with complete or nearly complete resolution after one to six treatments without cutaneous scarring or permanent pigmentary alteration.

Lasers in dermatology--1993.

Abstract: THERE HAS been a great increase in the understanding of laser tissue interactions in the 11 years since the last laser editorial in theArchivesby Arndt and Noe. 1 This has resulted in the development of numerous new-generation laser systems that take full advantage of the unique properties of laser light to achieve very specific and confined effects in tissue while minimizing collateral damage. All three laser studies in this issue of theArchivesare good examples of the progress that has been achieved. 2-4 ORIGINAL LASERS IN DERMATOLOGY The first laser to be used in humans was a ruby laser studied by Leon Goldman, a dermatologist, in the early 1960s. 5 He made numerous observations regarding laser tissue interaction with the ruby laser. He demonstrated specific laser effects on epidermal components of the skin and tested the laser on various benign as well as malignant lesions. 5-7 The

Spectral broadening of picosecond laser pulses in optical fibres

Abstract: Picosecond light pulses of a passively mode-locked ruby laser (pulse duration Δt L≈35 ps) are spectrally broadened in optical fibres of core diameters from 4 μm to 600 μm. Combining the effects of self-phase modulation, stimulated Raman scattering, and parametric four-photon interaction in an 8-μm core fibre of 4 m length with the effect of selective spectral attenuation in a ruby rod resulted in rather smooth spectra extending from 685 nm to 830 nm (spectral width ≈2300 cm-1).

Oxide and Fluoride Laser Crystals

Abstract: Crystals doped with metal ions have long been recognized as useful laser media. In fact, laser action was first demonstrated in 1960 on the basis of a ruby laser rod (or Cr3+-doped A1203) (I). Following the discovery that crystals doped with metal ions provide a viable route by which to develop solid-state laser media, hundreds of additional doped crystals have been shown to lase. Many of the early crystals that were of interest to researchers entailed well-known luminescent materials which, by happenstance, also exhibited laser action. Later, many new materials were developed specifi­ cally to serve as laser crystals. In spite of the proliferation of solid-state gain media, few crystals have proven to be useful under practical cir­ cumstances. In fact, the gap between demonstration exercises of laser action and the engineering of practical systems is often wide and difficult to bridge. In order to develop and test new laser crystals, it is first crucial to identify the appropriate means by which to grow and fabricate the crystals. To further optimize the crystal growth conditions, it is necessary to understand the basic physical properties of the melt and solid. In order to successfully

Optical imaging of shock waves produced by a high-energy electromagnetic transducer.

Abstract: An electromagnetic acoustic transducer (EMAT) and acoustic lens have been constructed to provide reproducible and well characterized acoustic shock waves in water. The peak pressure amplitude variation for the unfocused and focused shock waves was found to be within +or-5%. The focal region has been characterized both optically and by conventional piezoelectric pressure measurements. Optical investigations centre around ruby laser illuminated Schlieren and focused shadow imaging. The temporal resolution of the optical technique was determined by the ruby laser pulse length of 20 ns, giving a spatial resolution of 30 mu m for a shock front in water.

Single-ended infrared photothermal radiometric measurement of quantum efficiency and metastable lifetime in solid-state laser materials: The case of ruby (Cr/sup 3+/:Al/sub 2/O/sub 3/)

Abstract: A simple, self-consistent frequency-scanned photothermal radiometric (PTR) detection scheme was applied to the measurement of the metastable state de-excitation parameters of a ruby laser rod. The radiative quantum efficiency and lifetime in this material were calculated from the extrema of the photothermal phase and the amplitude slope versus the excitation laser beam modulation frequency curves, without recourse to the conventional second measurement to eliminate effects of photothermal saturation. This technique simplifies significantly the experimental methodology, guarantees uniqueness of the measured quantities, and increases the measurement range of lifetimes as compared to other photothermal-based methods. Therefore, it may prove valuable for fast industrial quality control, as well as for fundamental studies of laser materials. >

Experimental study of charge state distribution from KrF and ruby laser-produced plasmas

Abstract: The detailed angular charge distributions of the asymptotic plasma produced from carbon and aluminum targets by UV and visible laser pulses in the intensity range of 1011–1013 W cm−2 and pulselength range of 1–20 nsec have been measured using a single shot electrodynamic charge analyzer. The observed variation of average charge state as a function of velocity was determined from measurement and has been found to be approximately linear with no apparent dependence on angle of observation. For similar irradiation conditions, shorter‐wavelength radiation produces lower final charge states, as expected, from the higher interaction density in the initial laser produced plasma leading to enhanced recombination in the early stages of expansion of the plasma. The characteristics of the angular charge distribution can be qualitatively explained by considering the flow of the source plasma mapping different regions of the focal spot into different angles, relative to the target normal, in the expanding plasma.

A method of pulsed‐laser desorption of hydrogen

Abstract: An apparatus and an experimental procedure, mainly designed to investigate the thermodynamics and kinetics of hydrogen evolution in materials, are described. Employing a 30 ns ruby laser pulse as a heat source, this method probes H behavior at higher temperatures and on a much shorter time scale than classic thermal desorption. Precise calibration techniques for the laser fluence and the desorption yield have been developed. The absolute calibration agrees well with a measurement of the H content by elastic recoil detection. Particular attention has been paid to lateral uniformization of the laser intensity, to allow valid one‐dimensional modeling of laser heating and H evolution, and extraction of the activation energies and kinetic factors. As an example, a cursory study of intrinsic H in Be is presented. The method is also applicable to other volatile dopants.

Evidence of refractive index change by Ti indiffusion into LiNbO3 substrate as a result of multipulse free‐running ruby laser irradiation

Abstract: It is shown that the multipulse free‐running ruby laser irradiation of z‐cut LiNbO3 single‐crystalline samples with 400 A‐thick Ti deposits results, under certain conditions, in an efficient Ti indiffusion with minimum perturbation. Implanted zones exhibit optical characteristics appropriate for the preparation of optical devices.

Quantum efficiency and metastable lifetime measurements in solid state laser materials via lock-in rate-window photothermal radiometry: technique and application to ruby (Cr3+:Al2O3)

Abstract: The newly developed photothermal detection technique of rate-window infrared radiometry is applied to the measurement of the metastable state deexcitation parameters of a ruby laser rod. The technique employs a square laser pulse and monitors the infrared photothermal radiometric response of the sample. By applying the photothermal lock-in rate-window concept, the radiative lifetime and quantum efficiency of Cr3+:Al2O3 are measured with optimal SNR and simple, unambiguous interpretation from the extremum in the lock-in analyzer in-phase rate-window signal. This technique simplifies significantly the experimental methodology; optimizes the photothermal SNR, which is inherently low in conventional frequency or time-domain photothermal measurements; and offers extended measurement dynamic range for both radiative quantum efficiency and lifetime in laser materials, as compared to frequency-scanned harmonic detection. Therefore, rate-window infrared photothermal radiometry may prove a valuable tool for the combined measurement of metastable lifetime and nonradiative energy conversion efficiency in laser materials with fast deexcitation rates.

Application of off-axis holography to spray investigations: aberration minimization and size determination

Abstract: A holographic measurement system was used for the investigation of droplet size, density and velocity in the injection spray of a model diesel engine. The model engine consisted of a conventional injection pump and a test chamber that could be operated at high pressure and temperature to simulate the conditions in an operating diesel engine. The use of off-axis holography with a laser light sheet from a pulsed ruby laser helped to increase the maximum droplet density in the spray that could be resolved. Chromatic aberrations, introduced by the reconstruction of the holograms with a wavelength different from the recording wavelength, were minimized by careful choice of recording and reconstruction geometry. A new method for size determination was devised. The reconstructed images were recorded with a CCD camera and analyzed with the help of a personal computer. Software for automatic detection of 3-D particle position and velocity determination was developed.

Electro-optic frame photography with pulsed ruby illumination

Abstract: By combining the attributes of electro-optic shuttering and pulsed laser illumination in a large format camera system, we have developed a multi-frame image converter camera with a laser illuminator that produces sequential photographs of fast phenomena with very high resolution. The combination of the large size image plane (75 mm), short exposure time per frame (minimum 12 - 15 ns), and monochromatic laser illumination provides clear, sharp, front-lit images of surfaces and shapes with no degradation by luminous air shocks or motion blur. The unique modular design of the camera and the laser allow for a variety of configurations and applications. The current camera system produces eight independent pictures or four stereo pairs. A Q-switched ruby laser with multiple pulse capability provides individual illumination for each frame. This system has photographed a variety of fast phenomena including the first stereo sequential photographs of the initial formation and early time history of high velocity shaped-charge jets.

Initiating Reaction in Liquid Propellants by Focused Laser Beams

Abstract: Droplets of HAN-based propellants were exposed to initiation by focused ruby laser beam pulses and the extent of decomposition at atmospheric pressure was monitored by accurate measurement of the permanent gas volume generated. Apart from the practical objective of laser ignition, the method allowed the effect of various forms of preactivation to be studied. This included precursory electrolysis, preheating and dyeing of the liquid, as well as incorporation of various species in the gaseous plasma generated by focusing the beam in various media just outside the droplet. It is shown that prcactivation-e.g.,by precursory electrolysis-leads to substantially increased decomposition and that the various methods of presensitising the liquid propellants are cumulative only up to a common maximum. Beyond this. the dominant influence is the constitution of the gaseous plasma, with the inclusion of oxides of nitrogen producing the major effect. These observations are discussed in relation to both their underlying c...

Micron-size particles emission from bioceramics induced by pulsed laser deposition.

Abstract: Pulsed laser deposition of hydroxyapatite is applied to cover titanium medical prosthesis. Laser irradiation of ceramics by power-pulsed ruby laser produces high velocity micron-size particles emission with a narrow ejection plume directed normally to the target surface. Photoemitted particles are deposited on a metal surface at 400 degrees C to obtain a granular film, stoichiometric, polycrystalline, and very adherent to the substrate. Deposited films are highly biocompatible and may be used to induce osteointegration processes of the implanted prosthesis with the bone tissues. The comparison between laser and plasma spray depositions of bioceramics is discussed.

Pulsed laser melting and resolidification of metal silicide layers

Abstract: Ti, Fe, and Co silicide layers, 80–200 nm thick, on top of single crystal silicon substrate have been melted by 25-ns ruby laser pulses and the resolidified structures have been analyzed by transmission electron microscopy, X-ray diffraction, and Rurtherford backscattering spectrometry. Metastable phases and/or epitaxial layers are obtained upon solidifcation. The transient molten layer has been monitored by means of time-resolved optical measurements with nanosecond resolution; in all cases solidification velocity of the order of 1 m · s−1 was observed, and in one case liquid undercooling as much as 800 K was estimated.

Magnetic and transport critical current density of laser-irradiated Sm-Ba-Cu-O superconductor at 4.2 K

Abstract: The low temperature (4.2 K) magnetic and transport critical current density of laser-irradiated (Q-switched ruby laser, 694 nm, 30 ns) Sm-Ba-Cu-O ceramic superconductors prepared by the coprecipitation technique have been investigated. Laser irradiation did not significantly change the structural parameter and the critical transition temperatureT c but caused an appreciable increase in magnetic critical current densityJ mc and transport critical current densityJ tc . Inverse a.c. Josephson effect studies at 77 K showed a sharp decrease of microwave-induced d.c. voltage after laser irradiation. SEM studies revealed partial melting at grain boundaries and grain growth due to sintering which improves the interconnectivity in the network of superconducting grain structures after laser irradiation. These phenomenon are attributed to physical densification and consequent reduction in the total number of weak links between the superconducting grains. The significant increase ofJ mc andJ tc after laser irradiation is presumably connected with the creation of irradiation-induced mobile defects which act as pinning centers and, hence, stronger Josephson current paths between the superconducting intergrains.

Mechanisms of formation of a disturbed layer in p-type CdTe under the action of nanosecond laser pulses

Abstract: The low-temperature photoluminescence spectra were determined before and after exposure of p-type CdTe to nanosecond ruby laser pulses of power density below that needed to melt the material. An increase in the laser radiation dose resulted in accummulation of mechanical stresses in the surface layers and when the plasticity threshold of the crystal was reached, a dislocation network was formed and it falicitated stress relaxation

EMI ruby laser stroboscope and its application in terminal ballistics

Abstract: This paper describes the EMI ruby laser stroboscope and two examples of its application, the study of behind the armor effects of a KE-projectile and the initiation of HE (high explosive) by a hypervelocity debris cloud. The flash x-ray technique is the common method to visualize terminal ballistic and impact phenomena which are mainly combined with light flashes, dust, and fragment clouds. The laser stroboscope is a useful completion to the other techniques, it allows the visualization of long duration (1 ms) events with high-time resolution and high accuracy. At a frequency of 200 kHz, for example, about 260 frames are taken with the camera at exposure times less than 20 ns.

Stimulated two-photon-excited luminescence in stilbene crystals

Abstract: The energy of the two-photon-excited luminescence has been studied experimentally as a function of the energy of the monochromatic pump—a giant ruby laser pulse—in a molecular stilbene crystal. At pump power densities up to 108 W/cm2 this dependence is quadratic. Above 108 W/cm2, the behavior deviates from the quadratic law; the two-photon-excited luminescence signal increases sharply with a further increase in the pump power density. The efficiency of the conversion of the laser light (λ = 694.3 nm) into UV two-photon-excited luminescence is η = 0.1%. The coefficient of two-photon absorption is estimated from the experimental data on the transition from spontaneous two-photon-excited luminescence to stimulated luminescence. The result agrees satisfactorily with data in the literature. Conditions for raising the efficiency of the conversion of radiation on the basis of two-photon-excited luminescence in condensed molecular media are analyzed.

XPS study of laser-annealed ion-implanted GaAs

Abstract: Data on the effects of 140 keV Zn+ implanation of (100)GaAs and the consequent low-power pulsed laser annealing (LPPLA) on the composition of the surface layers are presented. The implantation does was 1014 cm −2 and the sample temperature was kept at 110 ± 10°C. THE LPPLA was carried out by 10–30 pulses of a Q-switched ruby laser (λ = 694.3 nm, τ = 25 ns and P0 = 4–6 MW cm−2) equipped with a spatial homogenizer. The crystal surface was studied by XPS analysis combined with depth profiling with the use of 1 keV Ar+. The results presented include the depth redistribution of oxygen and the As/Ga ratio as well as the oxide thickness for (a) virgin, (b) as-implanted and (c) implanted and then annealed samples.

Laser medicine in China

Abstract: Laser medicine is one of the earliest developed and most prominent branch of applications of laser technology. Since the first appearance of the ruby laser in 1960 it took only one year for the ruby laser retina coagulation machine to be found in the market. Accompanying the development of various species of new lasers, together with the development of fiber techniques and applications of electronics, tremendous progress has taken place on laser applications to biological and medical basic research as well as to laser medical treatment and diagnostics. Indeed, laser medicine is a multi-disciplined new technology and profession, and much more important developments are expected.

Status and issues in the development of a γ-ray laser. II. Giant resonances for the pumping of nuclei

Abstract: A γ-ray laser would stimulate the emission of radiation of wavelengths below 1 A from excited states of nuclei. However, the anticipation of a need for high pump powers tended to discourage early research and the difficulties in demonstrating a device were first assumed to be insurmountable. Over the past decade, advances in pulsed-power technology have changed these perceptions and studies have built a strong momentum. A nuclear analog of the ruby laser has been proposed and many of the component steps for pumping the nuclei have been demonstrated experimentally. A quantitative model based upon the new data and concepts has shown the γ-ray laser to be feasible if some real isotope has its properties sufficiently close to the ideals modeled. The greatest positive impact upon feasibility has come from the discovery of giant resonances for pumping nuclei that greatly reduce the levels of pump power needed.

Laser and thermal processing for Ti:LiNbO3 waveguide fabrication

Abstract: Ti diffusion into LiNbO3 single crystal was studied as a result of Ruby laser irradiation of a metallic Ti thin film covering the crystal surface and subsequent thermal processing in a furnace. Different regimes of irradiation and heating were used. SIMS analysis was employed for investigation of the treatment. The combined method used proved to be able to form waveguides of 3–4 μm thickness.