Pre-calculated relevant Nd: YAG laser parameters for optimized varicose veins treatment

Full clearance of enlarged veins, without side effects, had always been the ultimate dream of patients. Varicose veins’ treatment protocols were not very decisive and mostly associated with some side effects. The aim of this work is to demystify the exact dose of laser parameters; namely fluence and pulse duration, to successfully treat enlarged blood vessels in face, legs and arms without side effects. This necessitated the calculation of exact temperature rise of the targeted tissue before laser irradiation. The pre-calculated laser parameters required, for successful treatment, without side effects were tested to achieve optimum clinical results; using 1064nm pulsed Nd: YAG lasers for all skin photo types. For this work, two values of spot size (5mm and 3mm), variable pulse duration (15-30 ms), variable fluences (110-190 J/cm2) and variable skin cooling temperature (3-18 °C) were used. Pre and post-cooling were found necessary to ensure positive results and minimal discomfort.

Multisensorial Assessment of Laser Effects on Shellac Applied on Wall Paintings

The assessment of five different laser treatments in the conservation of wall paintings was devised on the basis of the surface temperature monitoring by infrared thermography (IRT), ultraviolet-induced fluorescence-visible (UV-VIS) imaging, and optical coherence tomography (OCT). A series of yttrium-aluminum-garnet (YAG) lasers were tested for removal of shellac layers from wall painting mock-ups. The mock-ups were realized as buon fresco with different mineral based pigments (earths and iron oxide) on a lime- and sand-based mortar. After the carbonatation process, all the samples were treated with shellac (5% in ethanol). The effects of neodymium (Nd):YAG, holmium (Ho):YAG, and erbium (Er):YAG laser sources, in different operative modes, on average temperature of the surface, color, and morphology were inspected with complementary sensors. The results show the necessity to adopt a combined approach in establishing safe laser operating conditions to avoid any undesired effects induced on the artefacts by the laser treatments. We demonstrate, for the first time, the performance of the Ho:YAG laser in the removal of a conservation treatment.

Improvement of Microstructure and Wear resistance of X12 Tool Steel by Using Laser Surface Re-Melting Technique

Nd-YAG lasers have been successfully used in recent years as reliable heat source to surface modification of engineering materials such as laser surface re-melting. In the present study, X12 tool steel was surface modified by using pulse Nd-YAG laser technique. Laser parameters are selected of 12 J pulse energy, 15 Hz frequency, 20 mm defocus length, 6 ms pulse duration, and 5.6 mm /s mm scanning speed. These parameters were chosen after undertaking trials to give suitable parameters in this process. Optical microscopy and backscattered scanning electron microscopy (SEM) with EDS and X-ray diffraction techniques were used to analyse the microstructure changes of the surface of tool steel. Wear resistance test was achieved by using a pin on disk method. The reason for this work is to improve the wear resistance for surface layer of tool steel after changes the morphology of the structure by rapid solidification during laser re-melting. In general, the structure consists of the dendrite and cellular structures with δ ferrite formed under conditions of rapid solidification without the primary coarse carbides. After laser melting, the results of the structure at the surface layers show an increase in wear resistance.

Mitigation of Thermal Effects in End Pumping of Nd : YAG and Composite YAG/Nd : YAG Laser Crystas, Modelling and Experiments-=SUP=-1-=/SUP=-

In this work, we have presented a finite element (FE) numerical modelling simulations to study and analyze the thermal effects in Nd : YAG and composite YAG/Nd : YAG laser rods. We have calculated the temperature distributions, stress intensity and thermal focal lengths at different pump powers for both rods. The FE simulations showed that using composite laser rod of undoped cap reduces the maximum value of stress intensity and thermal focal length by ~35% and ~ 50%, respectively. We have verified the FE calculations experimentally by direct measurement of focal length of thermally induced lens by using Hartmann-Shack wavefront sensor. Good agreement was obtained between FE calculations and experimental measurements. Keywords: Nd : YAG lasers, Thermal lens, Wavefront sensing, solid state lasers.

Realization of the Radiance Scale Using Transfer Function of the Laser-Based Optical System

This work aims to determine the radiance responsivity to be used in the calibration of polychromatic radiation sources with low uncertainty. To realize the radiance, Ar-ion, He-Ne, and Nd-YAG lasers as well as an integrating sphere with a 0.15 m diameter are used to obtain radiation sources having Lambertian distributions. Then, a silicon photodiode-based reflection-type trap detector with calibrated precision aperture, which is traceable to a liquid helium cooled laser-based cryogenic radiometer, is used to measure the photocurrent corresponding to each wavelength and thereby to obtain radiance. The proposed system, which measures the spectral current response of this laser-based radiance, is a double-grating monochromator with a 2 × 300 mm focal length and triple gratings in each of its turrets. First, the radiance of the laser beam that emerged from the integrating sphere is calculated, and then the radiance responsivity of the system is obtained by measuring the photocurrent outputted from the exit slit of the monochromator at each laser wavelength. Finally, the spectral radiance values of the polychromatic lamps are obtained using the radiance responsivity of the system. Consequently, the study aims to develop the derivation and better understand traceability of the other radiometric and photometric quantities with low uncertainty from the fundamental radiometric radiance unit. Measurement results obtained in the expanded measurement uncertainty scale are determined using both classical and Monte Carlo methods.