Showing papers on "Ruby laser published in 1971"
TL;DR: A Q-switched ruby laser was used to irradiate excised biological tissues and an isolated narrow band emission line was observed at 347 nm on irradiation of collagenous tissues.
Abstract: A Q-switched ruby laser was used to irradiate excised biological tissues. An isolated narrow band emission line was observed at 347 nm on irradiation of collagenous tissues. Temporal pulses at 347 nm were narrower than the laser pulses at 694 nm. Reduced crystalline glutathione yielded narrow band emission at 347 nm that was similar to that for the collagenous tissues. The observed narrow band emission at 347 nm is thought to be due to optical second harmonic generation.
190 citations
TL;DR: In this paper, the authors studied the suitability of focusing a passively Q-switched 30 J ruby laser beam for minimum ignition energy measurement, and found that the difficulties of the method are associated with the finite duration of the laser pulse.
Abstract: The plasma produced by focusing a passively Q-switched 30 J ruby laser beam is studied as regards its suitability for minimum ignition energy measurement. By comparison with electric spark discharges, it would appear to offer shorter times and smaller volumes of the initiating plasma, as well as freedom from energy losses to electrodes and elsewhere within the circuit. The growth of the initiating plasma as well as that of the flame kernel are studied as a function of pressure and composition, the former using an optical delay line with a schlieren system and the latter by high-speed schlieren streak photography. It is found that the difficulties of the method are associated with the finite duration of the laser pulse. In the time between the onset of breakdown and the end of the pulse the plasma front facing the incident beam absorbs the incoming energy, leading to the production of an extended and unsymmetrical initiating source, an absorption threshold which may already be in excess of the minimum ignition energy, and the formation of a blast wave which may be powerful enough to initiate a detonation rather than a deflagration. For a pulse of approx. 20 nano second half width these effects become serious above about half an atmosphere for stoichiometric methane-air mixtures. For lower pressures, or near limit mixtures, the promise of the method is borne out and both ignition energies and quenching distances fall below those determined by the electric spark method. For higher pressures and faster reacting mixtures it will be necessary to decrease the duration of the laser pulse and the size of the plasma.
88 citations
TL;DR: In this paper, a focused Q-switched ruby laser was used to generate a shock wave at the window-explosive interface when irradiated by a 1000-A-thick aluminum film.
Abstract: Immediate longitudinal detonations have been observed in confined small-diameter columns of PETN, RDX, and tetryl by using a focused Q-switched ruby laser. The energy ranged from 0.8 to 4.0 J in a pulse width of 25 nsec. A 1000-A-thick aluminum film deposited on a glass window was used to generate a shock wave at the window-explosive interface when irradiated by the laser. In some cases, steady-state detonations were reached in less than .5 microsec with less than 10% variation in the detonation velocity.
72 citations
01 Mar 1971
TL;DR: In this paper, a report is given of observations of the ionization of atomic cesium by the simulataneous absorption of three ruby laser quanta, showing that circularly polarized light produces ionization about twice as efficiently as linearly polarized light.
Abstract: : A report is given of observations of the ionization of atomic cesium by the simulataneous absorption of three ruby laser quanta. The results appear to be in qualitative agreement with theory, and indicate that circularly polarized light produces ionization about twice as efficiently as linearly polarized light, suggesting a new kind of polarized electron source. (Author)
56 citations
TL;DR: In this paper, a report is given of observations of the ionization of atomic cesium by the simulataneous absorption of three ruby laser quanta, showing that circularly polarized light produces ionization about twice as efficiently as linearly polarized light.
Abstract: : A report is given of observations of the ionization of atomic cesium by the simulataneous absorption of three ruby laser quanta. The results appear to be in qualitative agreement with theory, and indicate that circularly polarized light produces ionization about twice as efficiently as linearly polarized light, suggesting a new kind of polarized electron source. (Author)
52 citations
TL;DR: In this article, high-level recombination radiation emitted from silicon was studied, using a Q-switched ruby laser as the source of excitation, and Oscilloscope recordings of the luminescence show very rapid recombination.
51 citations
TL;DR: In this paper, the power-versus-wavelength characteristic for a high-power, continuously tunable far-infrared source has been experimentally determined and compared with theory, using a Q-switched ruby laser as the pump and stimulated polariton scattering in the crystal LiNbO3 as the scattering mechanism.
Abstract: The power‐versus‐wavelength characteristic for a high‐power, continuously tunable far‐infrared source has been experimentally determined and compared with theory. Utilizing a Q‐switched ruby laser as the pump and stimulated polariton scattering in the crystal LiNbO3 as the scattering mechanism, peak powers outside the crystal of ∼ 3 W at 200 μ are observed without crystal damage. Linewidth measurements indicate a bandwidth of < 0.5 cm−1 for the radiation over the observed tuning range 66–200 μ.
50 citations
TL;DR: In this paper, the absorption and polarization spectra from the first excited singlet state of pyrene and the absorption spectrum of the pyrene excimer were obtained by laser flash spectroscopy using a frequency doubled ruby laser pulse of 6 nanoseconds halfwidth.
47 citations
TL;DR: In this paper, a collisional mechanism was invoked to explain the anomalously long infrared laser pulses in cesium-helium vapor when helium buffer gas is present, and self-focusing of a ruby laser beam was also observed to occur in Cesium under certain conditions.
Abstract: Infrared laser action is observed to occur in vapors of K, Rb, and Cs photoexcited by various giant pulse laser beams. The mechanism of excitation involves two‐photon absorption by the molecular species followed by dissociation into various excited atomic states. In the case of cesium, anomalously long infrared laser pulses are obtained when helium buffer gas is present. A collisional mechanism is invoked to explain this phenomenon. Self‐focusing of a ruby laser beam is also observed to occur in cesium–helium vapor under certain conditions.
44 citations
TL;DR: In this article, the enhancement of the scattered signal due to the mixing of two optical beams in a plasma is observed, and the presence of enhanced oscillations is demonstrated by a 50% increase in the intensity of the satellite in the scattered light spectrum of a third beam.
Abstract: The enhancement of the scattered signal due to the mixing of two optical beams in a plasma is observed. The two beams are produced in a dual-cavity organic-dye laser pumped by a $Q$-switched ruby laser. The presence of enhanced oscillations is demonstrated by a 50% increase in the intensity of the satellite in the scattered light spectrum of a third beam.
43 citations
TL;DR: In this paper, a Q-switched ruby laser was used to induce the Insulator to metal phase transition in VO2 sputtered films within 20 nsec by using a He-Ne probe beam reflected off the film surface.
TL;DR: In this article, the outputs of a ruby laser and a tunable dye laser (pumped by the ruby laser) have been frequency-mixed in a proustite crystal.
TL;DR: In this article, laser emission from Rhodamine 6G and Rhodamine B both dissolved in ethanol has been observed using the focused 6943 A output of a giant-pulse ruby laser as a pumping source.
01 Jan 1971
TL;DR: An understanding of laser effects on dental structures would be difficult without first briefly describing dental hard and soft tissues.
Abstract: An understanding of laser effects on dental structures would be difficult without first briefly describing dental hard and soft tissues.
TL;DR: In this article, the cross section for simultaneous net absorption of $n$ photons by a system of two point charges has been calculated numerically for scattering in a ruby laser beam at an incident relative energy of 100 eV.
Abstract: In order to obtain information about the role of multiphoton processes in recently reported laser-induced nuclear fusion, the cross section for simultaneous net absorption of $n$ photons by a system of two point charges has been calculated numerically for ${e}^{\ensuremath{-}}\ensuremath{-}p$ scattering in a ruby laser beam at an incident relative energy of 100 eV. The results show that at laser intensities involved in fusion experiments multiphoton processes apparently play an important role, partly contributing to the same order within certain $n$ intervals.
TL;DR: In this paper, two methods for generating sound at microwave frequencies with a Q-switched ruby laser were presented, based on the modulation of the laser due to its mode structure and on the nonlinear properties of the solid.
Abstract: Two methods are presented for generating sound at microwave frequencies with a Q‐switched ruby laser. They are based on the modulation of the laser due to its mode structure and on the nonlinear properties of the solid. Sound is created at the laser modulation frequency. (1) Electrostrictive mixing in a LiNbO3 crystal, using a forward Brillouin scattering geometry, produces sound pulses at 800 MHz inside the crystal. Acoustic power densities were around 0.1 mW/mm2. (2) We then used surface heating of a metal film deposited on the surface of a dielectric crystal. At microwave frequencies, good efficiencies can be achieved; at 840 MHz, we generated in a gold film nearly 10 mW/mm2 of sound in 30‐nsec pulses.
TL;DR: In this article, the deviations from the Beer-Lambert's law of solutions of cryptocyanine were measured when the solutions were illuminated by a giant ruby laser pulse, and it was shown that a second absorption from an excited state is needed to explain the experimental results.
Abstract: The deviations from Beer—Lambert's law of solutions of cryptocyanine were measured when the solutions were illuminated by a giant ruby laser pulse. The transmission‐intensity curves show quite unambiguously that a second absorption from an excited state is needed to explain the experimental results. It is also shown that under steady state conditions it is the number of absorptions and not the detailed level scheme that governs the behavior of the system. The transmitted pulse was shown to be narrower than the incident one in an amount depending on incident intensity. Using the two absorption steady state mechanism, the change of shape could be explained and calculated. The decay rates and absorption cross sections were calculated for two models—the one which assumes absorption from an excited singlet, and the other which assumes absorption from the lowest triplet state. The blue fluorescence of cryptocyanine is explained in terms of our results. A level scheme based on the known spectrum fits with the suggested model.
TL;DR: The lifetime of the photoexcited state of the hydrated electron in liquid water at room temperature is shown to be less than 6 × 10−12 seconds following photoexcitation at 694 nm, a wavelength very close to λmax as mentioned in this paper.
Abstract: The lifetime of the photoexcited state of the hydrated electron in liquid water at room temperature is shown to be less than 6 × 10−12 sec following photoexcitation at 694 nm, a wavelength very close to λmax. This has implications concerning the nature of the optical transition involved and may suggest that the absorption band is a photoionisation efficiency profile rather than an electronic transition to a bound excited state. The absorbance of hydrated electrons (produced by uv flash photolysis) was measured at very high light fluxes using a Q‐switched ruby laser under conditions where cryptocyanine and methylene blue solutions showed marked nonlinear absorption due to saturation of optical transitions. Whereas the dye solutions showed diminished absorbance and a shortening of the laser pulse at high light intensities, hydrated electrons gave identical absorbance at all intensities, varied over 7 orders of magnitude, up to 200 photons per hydrated electron per cm2 of the light beam.
TL;DR: The resolution that has been obtained with the high powered laser and the observed durability of the dichromated gelatin holograms for very high energy densities are encouraging and suggest a number of possible applications.
Abstract: A holographic lens is used in conjunction with a pulsed ruby laser for machining single and multiple spots on a 0.12-μm thin film of tantalum deposited on glass. Spot sizes as small as 14 μm have been obtained with hologram diffraction efficiencies as great as 30%. Imaging of two spots separated by 3.18 mm has resulted in the simultaneous machining of two 30-μm spots having equal intensity and spot shape. The resolution that has been obtained with the high powered laser and the observed durability of the dichromated gelatin holograms for very high energy densities are encouraging and suggest a number of possible applications.
01 Jan 1971
TL;DR: In this article, results of experiments to determine retinal damage and lens damage caused by the Q-switched ruby laser are presented and theoretical considerations and calculations for retinal damages are discussed and compared with experimental results.
Abstract: : Results of experimental investigations to determine threshold levels for doubled neodymium and ruby lasers are presented The experimental animals were rhesus monkeys Threshold levels for retinal damage caused by the doubled long-pulsed and Q-switched neodymium laser are reported, and results of experiments to determine retinal damage and lens damage caused by the Q-switched ruby laser are presented In addition, theoretical considerations and calculations for retinal damage are discussed and compared with experimental results (Author)
TL;DR: In this article, a single-mode ruby laser was used to produce a plasma filament having transverse dimensions an order of magnitude less than the diameter of the focal region, propagating toward the laser beam, prior to the main plasma formation.
Abstract: Subnanosecond interferograms with high spatial resolution have been made of the sparks produced in several gases by the output of a single‐mode ruby laser. This has resulted in the observation of a plasma filament having transverse dimensions an order of magnitude less than the diameter of the focal region, propagating toward the laser beam, prior to the main plasma formation. The development of this filament is observed, and its production by a self‐focusing mechanism is discussed.
TL;DR: In this paper, the authors compare the histo-pathology and electron microscopy of short and long term retinal scars produced by both quasi-continuous ruby laser and short pulse xenon arc exposures.
Abstract: The problem of hypercoagulation and the occurrence of post-coagulative maculopathy have long been associated with xenon arc photocoagulation procedures. The virtual absence of these complications with pulsed ruby laser coagulations has led many workers to experiment with short pulse exposure techniques. We describe and compare the histo-pathology and electron microscopy of short and long term retinal scars produced by both quasi-continuous ruby laser and short pulse xenon arc exposures. Our results show, that both systems produce damage only in the outer retinal layer, and result in very similar scar formations, with no involvement of the inner plexiform or nerve fibre layers.
TL;DR: In this paper, the authors used a photoionization of TMPD to produce trapped electrons in ethanol and 3 MH glasses at 77°K by using pulses of 3471A light from a ruby laser.
TL;DR: In this article, the scaling relations for the front velocity with laser intensity and gas density are derived for many of the interaction models proposed in the literature, and only the gas-dynamic model with fluid motions induced during laser heating compares favorably with the data.
Abstract: The focused output of a ruby laser has been used to drive waves which travel in the same direction as the laser beam. The density gradient produced by expanding high‐pressure air or hydrogen into a vacuum was irradiated by the laser from the vacuum side of the jet. A luminous plasma was observed to propagate up the jet, through the orifice, and into the gas reservoir. Observations of this type have application to the study of comparable waves generated at the surface of a solid. Measurements of the luminous front velocity are reported over the gas density range of 1–7 amagats and laser power range of 100–500 MW. The scaling relations for this front velocity with laser intensity and gas density are derived for many of the interaction models proposed in the literature. Only the gasdynamic model with fluid motions induced during laser heating compares favorably with the data.
TL;DR: In this paper, the authors used a mode-locked neodymium laser as the intense light source and found that the operating wavelength of this laser, 1.06 µm, is such that a positive result would indicate excitation by three photon absorption.
Abstract: STUDIES of the blue fluorescence generated in solutions of certain organic dyes, for example, cryptocyanine, by the intense emission of a Q-switched ruby laser have demonstrated the two photon nature of the excitation process1,2. A similar fluorescence effect is observed in the pure solvent 1-chloro-naphthalene (CLNP) and attributed to two photon absorption in the tail of the strong band centred near 300 nm1,2. This intensity-dependent absorption is also thought to initiate the strong self-Q-switching effect observed when a cell containing the pure solvent is inserted in the cavity of a ruby laser3. There is no a priori reason to exclude higher order excitation processes if the incident light has the appropriate wavelength and so we have looked for the characteristic fluorescence of CLNP using a mode locked neodymium laser as the intense light source. The operating wavelength of this laser, 1.06 µm, is such that a positive result would indicate excitation by three photon absorption.
01 Jan 1971
TL;DR: In this article, the quantum flux G corresponding to the breakdown threshold E field is given by an equation which is approximately of the form ln 44 = ln[δt/A(G/ω)] - B(ω/G)1/2 where Δt and ω are the laser pulse length and frequency, and A and B are constants.
Abstract: Solving the quantum-kinetic equation for electrons interacting with deuterium molecules and a 1.8-eV photon field, we have made time-dependent calculations of the breakdown of deuterium gas by a ruby laser. We find that the quantum flux G corresponding to the breakdown threshold E field is given by an equation which is approximately of the form ln 44 = ln[δt/A(G/ω)] - B(ω/G)1/2where Δt and ω are the laser pulse length and frequency, and A and B are constants. The field strength thresholds which emerge from these calculations are compared with available experimental data, and good agreement is obtained.
TL;DR: In this article, a ruby laser with a maximum power of 80 MW (total energy of 1.2J) is focused on to a tip of a filament of polyethylene (CH2)n with a size of 0.2*0.2 mm2 suspended in a vacuum.
Abstract: Radiation from a ruby laser with a maximum power of 80 MW (total energy of 1.2J) is focused on to a tip of a filament of polyethylene (CH2)n with a size of 0.2*0.2 mm2 suspended in a vacuum. About one-tenth of the total energy is absorbed in the target. Measurements are performed with an ion energy analyzer (Eubank and Wilkerson, 1963) set up at an angle of 90 degrees from the laser incidence and with an electrostatic probe with twin electrodes. The ion species in the plasma is C2+ only. The distribution of ion energy has a peak at an energy of about 70 eV. A lack of hydrogen species is similar to the results obtained in the case of a lithium hydride plasma (Mattioli and Veron, 1969). It is found by mass analysis of the residual gas that the molecular hydrogen and methane components increase noticeably after a laser shot. The angular dependence of the expanding plasma is observed by measuring ion saturation currents to the probe. No magnetic field is applied.