Showing papers on "Ruby laser published in 1975"

A high-sensitivity laser microprobe mass analyzer

Abstract: A laser microprobe mass analyzer has been developed. It is intended for application in biomedical and physiological research. A frequency-doubled ruby laser is focussed through an incident light microscope to a spot of minimally 0.5 μm in diameter on a thin section specimen of 0.1–1.5 μm thickness. The microplasma generated from the irradiated volume is analyzed in a time-of-flight mass spectrometer recording the complete spectrum for each shot. From lithium doped epoxy resin (5 ppm by weight), used as an organic standard, 1.4×10−19g or 1.4×104 atoms of the6Li isotope have been detected. This sensitivity corresponds to that of ion microprobes but is at least an order of magnitude higher than obtained with electron probe X-ray microanalyzers.

Histopathology of ruby and argon laser lesions in monkey and human retina. A comparative study.

Abstract: Suprathreshold fundus lesions produced by ruby and argon laser photocoagulation were studied within 24 hours by light and electron microscopy. It was shown that damage was maximal in the outer retina in all ruby laser lesions and extramacular argon laser lesions. In both monkey and human, inner retinal damage occurred independently of outer retinal damage in macular lesions produced by the argon laser. In lesions produced by equal energy, inner retinal damage was more severe in humans than in monkeys. In both species outer retinal damage was less severe in the foveal than the parafoveal region and this disparity was greater in humans than in monkeys. These findings are important to the therapeutic use of argon laser energy for mascular disease. In particular, absortion of energy in the inner retina reduces the energy available in the treatment of subretinal lesions in the foveal area, and causes unwanted neuroretinal damage. The higher sensitivity to argon laser irradiation of the human fovea compared with the monkey fovea, has not been appreciated when defining laser safety limits.

A fast scalable switching technique for high‐power CO2 laser radiation

Abstract: Fast switching of high‐power 10‐μm radiation by reflection from optically induced carriers in polycrystalline germanium has been demonstrated. Initial studies carried out with a single‐mode TEA CO2 laser and a 2‐nsec ruby laser pulse have resulted in the generation of synchronized ∼2‐nsec pulses of 0.69‐ and 10‐μm wavelength. Potential applications of this technique include the selection of single high‐energy pulses from the mode‐locked output of large‐aperture CO2 lasers.

Enhanced nonlinear optical effects in rotationally twinned crystals

Abstract: We have produced continuously tunable infrared radiation between 4 and 21 μm by mixing the outputs of a ruby laser and a ruby−pumped dye laser in a single rotationally twinned ZnSe crystal. The peak output power of 5 W at 4 μm is approximately 250 times larger than the power obtained from an untwinned ZnSe crystal of comparable length. This enhancement is attributable to randomly spaced rotational twin planes perpendicular to the direction of propagation. Regularly spaced twins should produce an enhancement proportional to the square of the number of twin planes.

Spectral hole burning in dye solutions

Abstract: Using picopulses generated by a mode-locked ruby laser, we have measured the 3-8-A bandwidth of a hole burned in the 0-0 transition of cryptocyanine in methanol and demonstrated the inhomogeneous chatacter of this transition. The population-rate equations are written for an inhomogeneous transition with two and four energy levels interacting with continuous or pulsed excitation. Using the numerical solutions of this model together with the experimental result we determine a transverse relaxation time T_{2} = 0.6-1 ps for cryptocyanine in methanol.

Pulse stretching and shape control by compound feedback in a Q-switched ruby laser

Abstract: Feedback control is employed to stabilize the output of a Q -switched ruby laser. A computational model of the rate equations plus feedback terms is used to examine pulse shapes with changing feedback parameters. It is shown that a lengthened flat-top pulse cannot be obtained with negative feedback alone, a compound feedback arrangement is suggested to facilitate this. A practical laser system is constructed with an associated feedback loop, good agreement is found between theory and experiment. Pulses flat to within ±5 percent are obtained with durations up to 600 ns and are amplified with no apparent saturation. Output powers of 15 MW are achieved for hundreds of nanoseconds with a divergence of 7 mrad and a spectrum consisting of transform-limited lines separated by the axial mode spacing.

Three Photon Ionization of Alkali Atoms at the Ruby Laser Wavelength

Abstract: Single mode ruby laser radiation (694 nm) and an atomic beam apparatus have been used in the study of the three photon ionization of Na, K, Rb, and Cs atoms. The process in all cases is nonresonant, the observations being consistent with a rate given by W3F3 where F is the photon flux. The values obtained for W3l (linear polarization) and W3C (circular polarization) and the ratio W3c/W3l are discussed in relation to recently calculated results and the few other experimental results available. Discrepancies well beyond the assigned errors exist between experimental and calculated results.

A simple, reliable waveguide dye laser for ophthalmological applications.

Abstract: The principle of operation, construction, and performance of a compact waveguide dye laser, especially designed as a source of retinal photocoagulators, are described, The guiding effects produced by the thermal gradients induced by the pumping pulse and the use of closed resonator make the laser very reliable, simple, and with good pulse repeatibility. The construction is very simple and inexpensive. Except for flashlamps, which are commercial, no part of the laser requires sophisticated technology to be built or assembled; neither optical components have critical flatness and need careful alignment. The system does not need cooling, and slow recirculation of the solution, necessary to replace the degraded dye in the waveguide, is provided by a magnetically coupled 0.1 W electric motor. The dye cell, pump, and dye reservoir form a single component of the laser which can be easily extracted for inspection and replacement of the dye solution. The single, regular pulse emitted by the laser, its time duration (a few microseconds), the possibility to operate the laser at the absorption peaks of the ocular tissues make the laser better than the random spiking ’’passive’’ ruby laser or than the ’’explosive’’ Q−switched ruby laser for ophthalmological applications. If connected with a slit lamp, the laser should compete with the much more expensive ion gas lasers. Good retinal photocoagulations have been made in rabbits using a solution of Rhodamine 6G in ethanol. Retinal spots of rectangular shape of variable dimension but of constant energy density have veen produced by simply masking the exit window of the laser.

An interferometric investigation of laser−supported absorption waves

Abstract: Laser−supported detonation waves, other laser−supported absorption waves, and plumes of vaporized material were the subject of interferograms. Both instantaneous ruby laser interferometry and time−resolved argon laser interferometry were used to study these events. Qualitative behavior is seen in the interferograms which was not evident in photographic studies of these phenomena, such as the progress of radial shock waves and structure in the absorption zone. Abel inversion is used to obtain quantitative radial behavior of the change in the index of refraction. The differences between the laser−supported absorption waves ignited at the surfaces of several materials are discussed. Alumina specimens produced vapor plumes under these conditions whose temporal motion can be followed because of AlO absorption of the argon laser wavelength. The changes in the index of refraction were measured for similar events at the different wavelengths of the instantaneous and time−resolved interferometers and were used to ...

Laser action in 1,4–di [2–(5–phenyloxazolyl)] benzene vapor

Abstract: Some parameters of a POPOP vapor laser were determined. Second harmonic of the ruby laser radiation was used as the pump wave. The laser action was achieved when the longitudinal pump power density was 80 MW/cm2. The vapor temperature was varied from 265 to 310°C.

Induced focusing and defocusing of optical beams via a Raman−type nonlinearity

Abstract: Using a 5.7−MW single−mode ruby laser pulse at an intensity of 100 MW/cm2 through a 10−cm−long cell of benzene, we report the experimental observation of the induced focusing and defocusing of an externally generated Stokes probe beam on the high− and low−frequency side of the 992−cm−1 Raman line, respectively. This observation gives direct evidence of the dispersion in the real part of the nonlinear susceptibility tensor χ3 in the vicinity of a Raman mode.

Yield of singlet and triplet excitons from x‐ray and ruby laser excitation of anthracene single crystals

Abstract: A new method for determining the singlet:triplet yields for x‐ray and ruby laser excited anthracene crystals is described. It was found that the ratio is higher than has been reported for x‐ray excitation and lower than reported for ruby laser excitation. X‐ray excitation produces roughly equal numbers of triplets and singlets. Ruby laser excitation indicates that the intersystem crossing rate from the first excited singlet is 1.5±0.5×107 sec−1, which is larger than had been reported, but still smaller than for anthracene molecules in solution. The greater triplet yield produced by x irradiation is related to efficient spin–lattice relaxation in highly excited electronic states and neither spin–spin nor spin–lattice relaxation in the electron and hole ground states is important in the short time involved in geminate recombination.

Analysis of the radiation backscattered from a laser‐produced plasma

Abstract: The light backscattered from a plasma produced by focusing a 1‐GW Q‐switched ruby laser has been measured. The reflection coefficient of the plasma is of the order of 1–2% and the reflected energy increases with the incident energy. The backscattered light is Doppler shifted; the shift is not uniform but varies markedly along the focal spot indicating a concave reflecting layer penetrating into the target with velocities of (2–4) ×106 cm/sec. The second harmonic of the ruby laser is also present in the backscattered light.

Experimental surgery on cloudman s91 melanoma with carbon-dioxide laser

Abstract: The continuous wave CO2 laser lacks a number of draw-backs of the pulsed Ruby laser, and seems attractive for tumor surgery. We compared the CO2 laser with conventional surgery in experiments on mice bearing the Cloudman S91 melanoma. We had the same rate of local recurrence and lung metastasis in both techniques.

Laser stimulated chemical reactions and isotope separation

Abstract: A theoretical analysis is made of an isotope separation method based on chemical reactions stimulated by infrared laser radiation. It is shown that the anharmonicity of the molecular vibrations has practically no effect on the isotope separation coefficient. A description is given of an experiment in which the nitrogen isotopes were separated by the laser-stimulated reaction N2+O2→2NO. This reaction was stimulated in a cell containing air which was subjected simultaneously to ruby laser radiation and to a strong Stokes component generated separately by stimulated Raman scattering in liquid nitrogen.

Laser welding: The present state-of-the-art

Abstract: : The evolution of laser systems is briefly reviewed from the first successful operation of the ruby laser in 1960 to the present. Laser materials processing developments are then reviewed followed by general discussions of currently available high power laser equipment, laser welding performance, laser weld characteristics, and the properties of laser welds in metals and alloys. A discussion of current industrial laser welding applications is also included. The report constitutes an effort to comprehensively review the important developments in laser welding up to the summer of 1975. (Author)

CO2 Laser Induced Breakdown and Heating of Hydrogen in a Magnetic Mirror Field Geometry

Abstract: A 1 GW, 125 J CO2 laser pulse focussed by a 10 cm f.l. parabolic mirror has been used to induce breakdown and heating in 15 Torr hydrogen along the axis of a short 50 kG magnetic mirror field. Evolution of the breakdown plasma thus produced has been studied by high speed photography, ruby laser Thomson scattering, and a Mach–Zehnder interferometer. Results indicate an efficient radial confinement of plasma by the mirror field with an electron temperature much enhanced over that resulting from a fieldfree breakdown. Interferometric measurements show that breakdown results in a cylindrical plasma with an electron density minimum on axis in both cases. A monitor of the transmitted CO2 laser pulse indicates very incomplete coupling of laser radiation into the plasma column with the field applied, presumably due to refraction losses at the entrance boundary of the breakdown.

Characteristics of an argon−laser−pumped ruby laser

Abstract: The characteristics of a quasi−cw single−mode ruby laser which is pumped by an argon laser are described. Particular emphasis is given to aspects which govern the linewidth. By heterodyning two independent lasers, linewidths as narrow as 0.5 MHz have been observed, averaged over a few seconds.

Self-bending of a ruby laser beam in CdSxSe1–x semiconductor crystals

Abstract: Self-bending of a ruby laser beam with an asymmetric transverse intensity distribution was observed in CdSxSe1–x semiconductor crystals. The dynamics of self-bending was investigated during giant pulses. The maximum self-bending angle, of the order of 3°, was observed in a crystal of CdS0.1Se1–0.9.

Attenuation of giant laser pulses by absorbing filters.

Abstract: Three types of absorbing filters were tested for suitability as reproducible attenuators for a Q-switched ruby laser beam. None of the filters tested were irreversibly damaged when irradiated with pulses having peak powers up to 40 MW (beam cross section ∼10−4 m2). However, Tiffen Photar neutral density filters and Corning filters showed reversible photobleaching (optical saturation) at large pulse energies, while Kodak Wratten neutral density filters did not saturate.

Dye laser for holographic applications

Abstract: : The patent concerns a dye laser for holographic applications. Q switched ruby laser is used to pump the dye laser using Rhodamine-6G as the dye. The dye laser is pumped with a Q-switched ruby laser having its 6,943 A output beam frequency-doubled with a KDP crystal. The light beam of 3,472 A so obtained is applied to pump the dye laser in a longitudinal arrangement using a dispersing prism. The resultant tunable dye laser output is then applied for recording holograms. Multi-stage systems and cascade spectrum narrowing of the dye laser output are used to increase the overall efficiency for holographic applications.

Subnanosecond microscopic holographic interferometry of plasmas produced by 1‐nsec CO2 laser pulses

Abstract: Two‐dimensional distributions of the electron density within plasmas produced by 1‐nsec‐duration high‐intensity (≳1013 W/cm2) CO2 laser pulses on solid polyethylene targets have been obtained with the aid of microscopic holograhphic interferometry. Short 700‐psec pulses, derived from a synchronized ruby laser, were used to illuminate the interferometric system, which had a spatial resolution of ∼10 μ.

Tunable organic dye laser for resonance interferometry and holography

Abstract: A tunable rhodamine 6G dye laser based on the Raduga laser (with coherent pumping) has been developed and tested This laser works in single, double, and multifrequency modes with a pulse energy of 10$sup -3$ J and power of about 01 MW and is suitable for hologram applications The laser linewidth has been reduced to about 03 A The spatial coherence function of the laser output is examined by two independent methods (interference and holographic) The coherent zone (to a level of 02 relative to the center) of the front end of the laser has an area of 13 x 13 and 08 x 14 mm$sup 2$ (for ruby laser energies of 08 and 12 J) The values of the spatial coherence function (for a single laser pulse) obtained by two different methods (microphotometric measurements of the intensity distribution across the front of the laser and holography alone) are compared Holograms are made of two dimensional diffuse objects The densities of ground state sodium atoms in a DC arc and in the flame of an alcohol lamp are determined by resonance interferometry (AIP)