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Q-switched Laser (Q-switch + laser)

Distribution by Scientific Domains

Physics and Astronomy	57%
Medical Sciences	42%

Selected Abstracts

Areolar Cosmetic Tattoo Ink Darkening: A Complication of Q-Switched Alexandrite Laser Treatment

DERMATOLOGIC SURGERY, Issue 1 2002
Sung-Eun Chang MD
background and objective. Medical tattooing of the areola is widely performed in Korea. However, cosmetic tattoos containing flesh-tone, purple-red, and yellow dyes are sometimes resistant to Q-switched laser and may even become darker. method. Two Korean women in their 30s who had a mastectomy got light brown to red areolar medical tattoos but they were not satisfied with the shape and size of the tattoos. They underwent Q-switched alexandrite laser treatment with a 3 mm collimated beam at fluences of 7.5,8 J/cm2 in order to trim the irregular contour and reduce the diameter of the tattoos. results. Within 5 minutes a dark gray to black discoloration of the treated area was evident and remained dark for 6 weeks. Improvement was not noted after two further Q-switched Nd:YAG laser treatments. conclusion. Medical areolar tattoos should be approached with extra caution when attempting their removal with high-energy pulsed lasers such as Q-switched alexandrite laser and a small test site should be performed prior to treatment. [source]

Repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laser

LASER PHYSICS LETTERS, Issue 8 2007
H. Lei
Abstract A stable repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laser is presented. A 0.8 mm-thickness 7 mm-diameter Nd:YAG crystal at 1.6 at.% is adapted as active medium and the saturable absorber for passively Q-switched pulse generating, a 0.2 mm-thickness 6.8-mm diameter Cr4+:YAG piece was thermal bonded into the Nd:YAG after primary optical contact. By using pulse pump and controlling the duty cycle of electric pulse and temperature of laser diode, a 1 W C-mount packaged fast-collimated laser diode, we can continuously achieve repetition rate from 1 kHz to 10 kHz as active Q-switched laser. The delay time at 10 kHz is 90 ,s, while the single pulse energy is 2.8 ,J with pulse width of 2 ns. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Fully analytical simulation of Q-switched lasers

LASER PHYSICS LETTERS, Issue 6 2004
A. Hofer
Abstract The complete solution of the rate equations of a Q-switched laser, a system of two nonlinear coupled differential equations, is derived fully analytically with the aid of the Lambert W-function. In contrast to numerical methods the analytical solution allows to optimize the relevant laser parameters very efficiently. As compared to numerical calculations the analytical solutions lead to identical results and are obtained much faster and in a very elegant way. (© 2004 by ASTRO Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Influence of Nd co-doping on the Cr4+ content in PWO single crystal

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004
Weifeng Li
Abstract The formation mechanism of Cr4+ in PbWO4 (PWO) crystals is studied by optical absorption and X-ray excited luminescence (XEL) spectra. It is found that the concentration of Cr4+ depends not only on the initial amount of Cr3+ but more importantly on the coaddition of Nd3+. This material may be used as a new passive Q-switched laser in view of its high absorption coefficient in the NIR region. For Cr-containing sample, Cr3+ primarily replaces Pb2+ and results in large relaxation of lattice. In order to keep the scheelite structure, some Cr3+ ions are oxidized into Cr4+ and occupy W6+ sites. In the codoping case, Nd3+ preferentially substitute for Pb2+ and Cr is forced into W6+ sites in the form of Cr4+ to keep charge neutrality and structural integrity. This view is strongly supported by FT-IR spectra. The origin of the decrease and even extinction of XEL is also discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Successful Treatment of a Cosmetic Tattoo Using a Combination of Lasers

DERMATOLOGIC SURGERY, Issue 1 2004
Karen Rebecca Suchin MD
Background. Cosmetic tattoos are becoming more popular and are often composed of several colors. Tattoo pigments containing ferric oxide and titanium dioxide can change to a blue-black color after exposure to Q-switched lasers that can be permanent. Objective. Using a patient who presented with rouge tattoos on the cheeks as an example, we describe a useful approach to laser treatment of cosmetic tattoos. Methods. Test areas were done with the Q-switched Nd:YAG at both 532 and 1064 nm and with the pulsed-dye laser at 595 nm. Results. Although an immediate blue-black color change occurred after treatment with the Nd:YAG at 532 and 1064 nm, sequential treatments at 1064 nm produced a near complete clearance of the tattoos. The pulsed-dye laser was used to remove subtle pink tones. Conclusion. Performing small test areas before complete treatment and using several laser wavelengths throughout the course of therapy are essential to the successful treatment of cosmetic tattoos. [source]

Fully analytical simulation of Q-switched lasers

Efficacy of laser treatment of tattoos using lasers emitting wavelengths of 532 nm, 755 nm and 1064 nm

BRITISH JOURNAL OF DERMATOLOGY, Issue 2 2004
B.M. Prinz
Summary Background Multifunctional laser devices can be used to treat tattoos successfully. Objectives To report the efficacy of laser treatment in professional, amateur, accidental and permanent make-up tattoos from our own experience and to compare it with the literature. Methods We retrospectively studied 74 consecutive patients with professional, amateur, make-up and accidental tattoos between June 1998 and November 2000. Patients were treated with a Q-switched Nd:YAG laser (wavelengths of 532 nm and 1064 nm), a Q-switched alexandrite laser (755 nm) and a variable pulse Nd:YAG laser (532 nm). Results Fourteen patients (19%) achieved a complete response (> 95% lightening of treated tattoos), 23 (31%) an excellent response (76,95% lightening) and 21 (28%) a good response (51,75% lightening). Sixteen patients (22%) showed only a slight improvement (, 50% lightening). Make-up tattoos and blue,black professional tattoos were most successfully treated. Multicoloured professional tattoos needed more treatments (mean ± SD 5·7 ± 5·4) in comparison with single-colour tattoos (3·5 ± 2·0). The amateur tattoos needed fewer treatments (2·8 ± 1·1) in comparison with professional tattoos. With accidental tattoos the results depended on the particles which had penetrated the skin. In contrast to literature reports, newer tattoos showed a trend to better treatment results than older tattoos. Conclusions Using modern Q-switched lasers, tattoos are removed successfully with minimal risk of scarring and permanent pigmentary alterations. Even multicoloured tattoos can be treated successfully and with a low rate of side-effects. [source]