Showing papers on "Ruby laser published in 2004"

Hair removal with intense pulsed light.

Abstract: The use of light and laser for hair removal has evolved during the past few years. Laser systems such as the ruby laser (694 nm), alexandrite laser (755 nm), diode laser (810 nm) and neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (1,064 nm) are commonly used in hair removal. However, permanent hair removal has been difficult to achieve using lasers owing to the long growth/rest cycle of normal human hair follicles. There is still an increasing demand for safer and more efficient hair removal techniques. The latest and most effective choice in the treatment of hair removal is non-coherent intense pulsed light (IPL), which is both efficient and safe for hair removal. A group of 210 patients with skin type III-V were treated for superfluous hair in different areas of the body (face, extremities, axillae, bikini line and back) for three to five sessions at 6-week intervals using IPL. There was a significant hair reduction of about 80% with no side effects and minimal complications. Follow-up was done 6 months after the last session. In conclusion, IPL is very effective and safe for hair removal.

10 kHz repetitive high-resolution TV Thomson scattering on TEXTOR

Abstract: In December 2003 a new 10 kHz multiposition Thomson scattering diagnostic with high spatial resolution has become operational on the TEXTOR tokamak. The system is the follow up of the high-resolution double-pulse Thomson scattering diagnostic. The conventional ruby laser has been replaced by a 10 kHz intracavity laser system and the spectrometer detector has been upgraded with two ultrafast complementary metal–oxide–semiconductor cameras combined with a special image intensifier stage. In the initial phase of operation, a burst of 18 pulses decaying from 17 to 8 J, with a repetition rate of 5 kHz, could be extracted from the laser. At a laser energy up to 12 J per pulse, ten electron temperature and density profiles were measured with an observational error of 10% on the electron temperature (Te) and 5% on the electron density (ne) at ne=2.5×1019 m−3 per spatial element of 12 mm. The resolution of the detection optics enables to sample either the full plasma diameter of 900 mm with 120 spatial channels of...

The Evolution of Surface Structures in p -CdTe Crystals under Pulsed Laser Irradiation

Abstract: The dynamics of modification of the surface structure in p-CdTe (111) crystals subjected to nanosecond ruby laser pulses with a lasing wavelength within the fundamental-absorption region (ℏω=1.78 eV) is studied. It is shown that, depending on the radiation dose, the surface morphology changes in the following order: the formation of tellurium film, an increase in the density of dislocations under the tellurium film, and the formation of ordered quasi-periodic structures of both micrometer and nanometer size. The size of the structures and the character of their distribution are shown to be dose-dependent.

Ruby laser treatment of congenital melanocytic nevi: a review of the literature and report of our own experience.

Abstract: The authors describe the possibilities and advantages of ruby laser treatment of large congenital nevi as an alternative to surgical excision. The literature (from 1980 to 2002) is reviewed and a case report is presented. Literature and the authors' experience show good cosmetic results after ruby laser treatment. Skin texture is improved and there is a considerable reduction in pigmentation and unsightly hair growth. Ruby laser treatment does not result in scarring, mutilation, or functional impairments, in contrast to surgical treatment. Only short outpatient sessions are required, recovery periods are extremely short, and no rehabilitation period is needed. No malignant changes have been reported after treatment with the ruby laser, even after 8 years of follow-up. The results imply that ruby laser treatment could be a valuable new treatment modality for large congenital nevi. It should be considered when patients refuse to undergo surgery, or when surgery would cause severe morbidity. More research should be initiated to assess possible risks and long-term results.

Laser action on magnesium and aluminium targets

Abstract: The beam of a ruby laser was focused onto two targets, 12Mg and 13Al, the irradiance being 140 GW/cm2. In both cases similar processes developed. Time resolved spectra in the region 9-23 nm showed highly ionized atoms. The electron temperature (about 50 eV) and the ion velocities (about 106 cm/s) were investigated. Due to plasma explosion, deep craters with radial jetting are shown on the target surfaces. Ripples around the craters are explained by spreading of sound waves, laterally deposited plasmas were mixed with expanding target particles.

Histological hair removal study by ruby or alexandrite laser with comparative study on the effects of wavelength and fluence.

Abstract: BACKGROUND: Several different laser systems are currently used to remove unwanted hairs. In this study, we studied follicular changes following hair removal with ruby or alexandrite lasers at different fluences.METHODS: Unwanted hairs were treated with a ruby laser (Chromos 694, ICN PhotonIcs, UK) at 10, 14 or 18 J/cm2 or with an alexandrite laser (LPIR, Cynosure, USA) at 11, 14 or 17 J/cm2. A 3 mm skin punch biopsy was taken immediately after each laser exposure and also 1 month later. Specimens were stained for histological observation. They were observed using immunohistochemistry with antibodies recognizing factor VIII related antigen or PCNA, and also by the TUNEL method. Similarly, electron microscopic observation was examined.RESULTS: Immediately after the laser exposure, moderate follicular damage was observed following treatment with either type of laser. One month later, cystic formation of hair follicles and foreign body giant cells were observed in skin treated with either type of laser. A sim...

Phase transformations induced in CdTe single crystal by ruby laser pulsed irradiation

Abstract: Phase transitions induced by laser irradiation in CdTe wafers have been studied in situ and experimental and computer simulation methods. The samples were irradiated by ruby laser with pulse duration 80 ns in energy density range from 0.02 to 0.5 J/cm 2 . Time-resolved reflectivity (TRR) measurements were carried out at the wavelengths of λ 1 =1.064 μm and λ 2 =0.532 μm. Dynamics of transmissivity was studied at λ 1 . Photoluminescence of CdTe, excited by the ruby laser single pulse, was also investigated. The character of TRR transients changes with the increase of irradiation energy density. The changes are more considerable at λ 1 than at λ 2 . The time dependencies of reflectivity are explained by the changes of optical parameters of CdTe in course of laser-induced melting, solidification and evaporation. The experimental data obtained from transmissivity and photoluminescence measurements correlate with those from TRR transients. Laser-induced melting, crystallization and evaporation processes were studied on the basis of the computational solution of a two-phase moving boundary problem with two moving interfaces. The calculated dependency of melt duration on energy density is in a reasonable agreement with experimental data. From our investigation it follows that in the molten state CdTe is characterized by constant or weakly changing reflectivity in the temperature range from T m to 3000 K.

Incorporation of fast laser beam shunting and a broadband polarizer in the MAST Thomson scattering systems

Abstract: Both ruby laser (300 points) and NdYAG laser (19 points) Thomson scattering systems are used on MAST. Fast nonlinear optical switching shunts laser beams from the four 50 Hz NdYAG lasers to obtain coaxial plasma illumination. The technique allows for future expandability to many laser systems. The ruby laser system is used in parallel. A broadband thin-plate polariser, based on nanotechnology, has been incorporated in the collection optics. It has a wide field of view and it almost halves the detected laser stray light and plasma background for both laser spectral regions. This allows much of the collection optics to function effectively in both spectral regions simultaneously.

Atomic-force microscopy and Raman scattering studies of laser-induced structural disordering on the p-CdTe surface

Abstract: Atomic-force spectroscopy and Raman scattering are applied to study structural modification of the p-CdTe (111) surface under exposure to pulsed multimode ruby laser radiation of nanosecond duration and a power density below the material-melting and destruction thresholds. It is shown that irradiation of crystals produces nanometer quasi-ordered surface nanoclusters 1.0–11.3 nm in height with a lateral size of 41–336 nm. Possible mechanisms of their formation are discussed.

The change in optical characteristics of ZnO crystals under ruby laser irradiation

Abstract: The influence of pulsed ruby laser irradiation on luminescence and optical transmission spectra of nominally undoped ZnO single crystals was investigated. Both treatment and measurements were performed at 300 K. The irradiation was found to cause the increase of crystal transmission in absorption edge region and the rise of shortwave wing of exciton luminescence with respect to its longwave one. These changes were accompanied with the rise of electric conductivity. The analysis of obtained results in common with earlier data led to the conclusion that the movement of mobile shallow donors from dislocations to crystal bulk took place under the influence of ultrasound wave excited by laser pulse. The decrease of shallow donor density near dislocations resulted in the shrinkage of c-band state density "tail" in these regions, which caused the shift of the optical absorption edge to the shortwave side.

Microwave discharge initiated by laser spark in air

Abstract: The possibility of laser spark initiation of microwave discharge in quiescent air under the atmospheric pressure has been investigated. Laser spark is created by impulse Ruby laser (6943 A, 0.22 J pulse energy and 25 ns-pulse duration) in focal point of short-focus lens (12 mm). This point is placed in the vicinity of the main maximum of MW-field in the focal area of parabolic mirror. The X-range impulse MW generator with output power 180 kW and pulse duration 1,2 µs via radiating system illuminates the focal area. Digital synchronous Schlieren system is used for visualisation of shock wave structures, exciting by laser spark and initiated MW discharge. The time delays between laser impulse, MW impulse and impulse of Schlieren registration (0,5 µs) are managing by the CAMAC system. Luminosity of discharges is measured by fast PMT (time resolution better than 30 ns). The range of time-shifts between laser spark and MW pulse 15-210 s is investigated. Our results show that semi-self-maintained MW discharge can arise during the time window, corresponding to decaying phase of laser -induced plasma. Contribution of MW energy in plasma luminosity has distinct maximum under the Laser-MW delays 80-110 µs, duration of this discharge is defined by MW impulse. For the Laser-MW delay 85 µs the series of shock-wave pictures is recorded. They clearly show the weak quasi-spherical shock wave structure originating due to MW energy contribution. Thus, the first important step for MW discharge position control by laser-ignited spark is made, in spite the results of this work have a preliminary character. The developing technique may become a promising way for creating of spatially compact MW discharges with predictable shape and position for plasmadynamic applications.

Advances in Light-in-Flight HPIV for the Study of Wind Tunnel Flows

Abstract: The concept of light-in-flight holographic particle image velocimetry (LiF-HPIV) has been demonstrated successfully for ruby laser light illumination and virtualimage reconstruction. To circumvent the many disadvantages of ruby lasers the method was transferred to illumination with pulsed second-harmonic Nd:YAGlaser light. Furthermore, real-image interrogation was employed to minimize alignment and calibration problems. By using cw Nd:YAG lasers it is possible to design an optical set-up for the reconstruction that is separate from the recording equipment. Thus, the time-consuming interrogations no longer block the flow measurements.

The incidence of side effects after laser hair removal

Abstract: Despite the widespread use of lasers for hair removal there is little data published on the incidence of side effects from this treatment. We aimed to generate data on a large number of patients receiving laser hair removal to obtain an accurate assessment of the incidence and type of side effects resulting from treatment. A multicentre prospective study of patients attending for laser hair removal was conducted to determine incidence of side effects in relation to skin type and laser(s) used. Laser hair removal is associated with a low incidence of side effects which are self-limiting in the majority of cases. Highest incidence of side effects was seen in darker skinned patients treated with the long pulsed ruby laser. Laser hair removal is inherently safe. For darker Fitzpatrick skin types the long pulsed Nd:YAG laser is preferred to the ruby laser.

On the angular spectra of anti-Stokes stimulated Raman scattering under self-focusing

Abstract: It is shown in this work, by the example of the first anti-Stokes component in toluene, that a high efficiency of conversion of laser radiation into the Stokes component in the focal regions of self-focusing (SF) plays a decisive role in the formation of the angular structure of radiation. The inclusion of a high efficiency of pumping conversion into the Stokes component in SF allows the basic regularities of the formation of the angular structure of an anti-Stokes radiation to be determined. The length of the domain of existence of the nonlinear polarization at the anti-Stokes frequency is expressed in this case in terms of optical parameters of a light-scattering medium, where this quantity is introduced by way of matching the calculated and the observed angles of preferable radiation. Moreover, the longitudinal distribution function of the nonlinear polarization turns out to be distinct from the Gaussian one proposed previously. The results of the calculations carried out are compared with experimental data obtained for toluene in a cell 25 cm long in which SRS was excited by single pulses 20 ns long with an energy of 0.6 J from a ruby laser with passive Q-switching.