Showing papers on "Ruby laser published in 2017"

The double-resonance enhancement of stimulated low-frequency Raman scattering in silver-capped nanodiamonds

Abstract: Hybrid plasmonic-dielectric nano- and (sub)microparticles exhibit magnetic and electrical dipolar Mie-resonances, which makes them useful as efficient basic elements in surface-enhanced spectroscopy, non-linear light conversion and nanoscale light control. We report the stimulated low-frequency Raman scattering (SLFRS) of a nanosecond ruby laser radiation (central wavelength λ = 694.3 nm (full-width at half-maximum ≈ 0.015 cm−1), gaussian 1/e-intensity pulsewidth τ ≈ 20 ns, TEM00-mode pulse energy Emax ≈ 0.3 J) in nanodiamond (R ≈ 120 nm) hydrosols, induced via optomechanical coherent excitation of fundamental breathing eigen-modes, and the two-fold enhancement of SLFRS in Ag-decorated nanodiamonds, characterized by hybrid dipolar resonances of electrical (silver) and magnetic (diamond) nature. Hybrid metal-dielectric particles were prepared by means of nanosecond IR-laser ablation of solid silver target in diamond hydrosols with consecutive Ag-capping of diamonds, and were characterized by scanning elect...

Histopafhology of Continuous Wave Neodymium: Yttrium Aluminum Garnet and Diode Loser Contact Transscleral Lesions in Rabbit Ciliary Body

Abstract: Neodymium: yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation has been shown to be an effective method of lowering intraocular pressure (IOP). Transmission and absorption features of diode laser radiation (810 nm) make these new laser sources suitable for production of transscleral thermal lesions. The transscleral effects on rabbit ciliary body of Nd:YAG and diode laser wavelengths were compared using a CW Nd:YAG laser and a CW Aluminum Gallium Arsenide diode laser. Both lasers were delivered by silica optic fibers, 600 jum in diameter. Eight rabbits were treated by applying the optic fiber 0.5 mm from limbus while increasing energy values from 0.2-2 J. The lesions produced at equal energy values underwent gross and histologic and ultrastructural comparison. Gross examination revealed threshold lesions at 1 J energy for the Nd:YAG laser and 0.8 J for the diode laser. The diode laser produced transscleral thermal lesions of the rabbit ciliary body comparable to those achieved by the Nd:YAG laser. The histologic and ultrastructural study showed that diode laser radiation produced more remarkable damage to the ciliary pigmented structures, causing deep coagulation necrosis of the pigmented epithelium, wide disorganization of the collagen in the stroma, and intravascular coagulation phenomena in the ciliary vessels. Before the introduction of these new laser sources in clinical transscleral procedures, further investigation is needed to determine optimal energy levels. Invest Ophthalmol Vis Sci 32:1586-1592, 1991 Contact transscleral Neodymium: Yttrium Aluminum Garnet (Nd:YAG) laser photocoagulation of the ciliary body has been shown to be an effective method of lowering intraocular pressure (IOP) in both animal and human eyes. 1 ' 2 Several laser sources have been used to control refractory glaucomas by transscleral photocoagulation of humor secretory structures. Weekers et al 3 reported their experience with the xenon arc system. Beckman et al 4 described the results obtained in decreasing IOP in glaucomatous human eyes with a pulsed ruby laser. In 1984, Peyman et al 5 presented a comparative study in which contact transscleral cyclophotocoagulations were produced in monkey eyes by argon and krypton lasers. Recently reported successful results, using the Nd:YAG laser,

The Treatment of Pigmented Lesions in Taiwan

Abstract: Combined dyspigmentation such as lentigines intermingled with freckles, or melasma with acquired bilateral nevus of Ota-like macules, are common among women in Taiwan. There are various lasers available, including Qswitched Nd-YAG laser, Q-switched alexandrite laser, Q-switched ruby laser, and pico laser. We conducted a literature review to understand the current practice of treatment for pigmented lesions in Taiwan.

through mirror M2 which is transparent at this Stokes frequency. As it is the case with active

Abstract: High efficiency pulse compression using Raman induced cavity dumping has been studied theoretically and experimentally. Through stimulated Raman scattering the electromagnetic energy at a primary frequency is down -converted and extracted from a storage cavity containing the Raman medium. Energy storage may be achieved either at the laser frequency by using a laser medium inside the storage cavity, or performed at a new frequency obtained through an intracavity nonlinear process. The storage cavity may be dumped passively through stimulated Raman scattering either in an oscillator or in an amplifier. All these cases have been studied by using a ruby laser as the pump source and compressed hydrogen as the Raman scatter. Results differ slightly accordingly to the technique used, but pulse shortenings higher than 10 and quantum efficiencies higher than 80 % were obtained. This method could also be used with large power lasers of any wavelength from the ultraviolet to the farinfrared spectral region.

Allemand de Recherches

Abstract: Holographic cinematography with the help of a pulse YAG laserP. Smigielski, H. Fagot, F. AlbeInstitut Franco -Allemand de Recherches de Saint -Louis (ISL)12, rue de l'Industrie 68301 Saint -Louis, FranceAbstractFor many years opticists have tried to achieve 3D- cinematography with the help of holo-graphy. The term "cineholography" has been introduced in 1965. At that time the methodconsisted in superimposing on the same photographic plate various holograms recorded atdifferent times. The image separation was achieved by rotating either the plate in its planeor the reference beam during both the recording and reconstructing processes. The number ofviews was limited by the principle itself, but a high repetition rate (100 kHz) has beenobtained with a pulsed ruby laser.Then other experiments have been conducted by different authors, mainly in the SovietUnions and in the United States of America, by using the principle of classical cinemato-graphy in which the image separation is obtained by translating the film. With this methodwe have recorded the first French holographic movies on 35 mm Agfa films with the help ofa pulsed YAG laser built in our laboratory. This frequency doubled laser (X = 0.532 pm)delivers pulses of 20 ns with an energy of 30 mJ at a repetition rate of 24 Hz.The experimental arrangements are described and some images of diffuse moving objects arepresented. The volume of the recording scene is greater than one cubic meter. The coherencelength of the laser is higher than one meter and remains steady during the recording process.Results are discussed and an outlook on the future is given with special respect to highrepetition rate techniques.IntroductionFor a number of years great efforts have been made to perform three -dimensional cinemato-graphy on the basis of holography. The term "cineholography" was introduced in 1965 [1].Thecineholographic method is characterized in that various holograms recorded at successivetime instants are superimposed on the same photographic plate. The images are separated byrotating the plate in its plane or by varying the inclination of the reference beam in boththe recording and reconstructing processes. The total number N of views is strongly limitedby the principle inherent in this technique (N =2 tr /8, e thereby denoting the angle at whichthe specimen is seen from the hologram) whereas the brightness of the reconstructed imagesdiminishes according to 1 /N2[2]. However this method allows to attain very high repetitionrates (100 kHz) required for investigating ultra -rapid phase objects [3]. Another techniquehas been used in Great Britain for recording holograms of objects transilluminated at highrepetition rates (10 to 20 kHz). Here the photographic plate is immobile and the variousholograms are separated on the photographic plate (and not superimposed like in the previouscase) with the aid of a mechano -optical deflection system [4]. In this method a particularhalf- scattering plate is used to generate simultaneously both the object beam and referencebeam such that the size of the scene to be recorded is somewhat limited.Comparable repetition rates (10 to 20 kHz) are attained in separating the elementaryholograms by the rotation of the photographic plate or by the rotation of a disk placedahead of the plate and provided with a series of apertures [5]. Once more the hologramsrecorded are those of transparent objects. Still higher repetition rates can be attained(GHz range) such that plasmas can be investigated with an experimental device which doesnot include any mobile component. The incident laser beam is split into ten parallel partswhich are shifted in space by means of a set of prisms and shifted in time with the aidof optical delay lines [6].Simultaneously experiments have also been conducted by other authors, chiefly in theSoviet Union [7] and in the United States of America [8]. These experiments were basedon the principle of conventional cinematography in which the images are separated by trans-lating the film. The holograms of objects which scatter light by reflection are recordedon 70 -mm- movies at a low repetition rate (maximum rate equal to 24 Hz). The method used inthe Soviet Union allows the image to be observed by several persons via a holographic screen.The source of light used for the recording process is a ruby laser such that it is notpossible to attain the cinematographic repetition rate (24 Hz) unless many ruby lasers areused. The experiments performed in the United States allowed a repetition rate of 20 Hz tobe attained with the help of a YAG laser, but the scene recorded is very small (small objectrotating at a speed of 1 r.p.s.) because of the limited power output of the laser (7 mJ).

Nonlinear Optical Phase Conjugation for Laser Systems

Abstract: This paper deals with certain nonlinear effects that can directly generate a wavefront which is the phase conjugate of the incident field. These phenomena can be exploited in pulsed laser systems to remove aberrations in the optical train as well as aberrations arising from turbulence in the atmosphere. We discuss our measurements of the effectiveness of this conjugation process using a ruby laser and stimulated Brillouin scattering in a CS2 waveguide device. Measurements are made of the divergence angle of the beam after correction. The application of conjugate processes realizable in SBS, SRS, parametric downconversion, and four -wave mixing is considered for typical CO2 laser systems. System gain, backscatter limitations and parasitic oscillation are discussed for typical pulsed amplifier systems. Amplified spontaneous emission and unwanted glint returns from optical defects appear to be the most serious limitations.