scholarly journals Effects of Laser Fluence and Pulse Overlap on Machining of Microchannels in Alumina Ceramics Using an Nd:YAG Laser

2019 ◽  
Vol 9 (19) ◽  
pp. 3962 ◽  
Author(s):  
Muneer Khan Mohammed ◽  
Usama Umer ◽  
Osama Abdulhameed ◽  
Hisham Alkhalefah
Keyword(s):  
Laser Fluence ◽  
Nd:Yag Laser ◽  
Yttrium Aluminum Garnet ◽  
Laser Pulses ◽  
Bottom Width ◽  
High Pulse ◽  
Peak Fluence ◽  
Different Depths ◽  
Micro Features ◽  
Shape Complexity

The quality of micro-features in various technologies is mostly affected by the choice of the micro-fabrication technique, which in turn results in several limitations with regard to materials, productivity, and cost. Laser beam micro-machining has a distinct edge over other non-traditional methods in terms of material choices, precision, shape complexity, and surface integrity. This study investigates the effect of laser fluence and pulse overlap while developing microchannels in alumina ceramic using an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Microchannels 200 µm wide with different depths were machined using different laser peak fluence and pulse overlap (percentage of overlap between successive laser pulses) values. It was found that high pulse overlaps and fluences should be avoided as they give rise to V-shaped microchannels i.e., 100% bottom width errors. The optimal peak fluence range was found to be around 125–130 J/cm2 corresponding to 3–5 µm depth per scan. In addition, channels fabricated with moderate pulse overlap were found to be of good quality compared to low pulse overlaps.

scholarly journals High-quality percussion drilling with ultrashort laser pulses

2021 ◽  
Vol 127 (9) ◽  
Author(s):  
A. Feuer ◽  
R. Weber ◽  
R. Feuer ◽  
D. Brinkmeier ◽  
T. Graf
Keyword(s):  
Stainless Steel ◽  
Laser Fluence ◽  
Ablation Threshold ◽  
Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
High Quality ◽  
Edge Quality ◽  
Ultrashort Laser ◽  
Percussion Drilling

AbstractThe influence of the laser fluence on the quality of percussion-drilled holes was investigated both experimentally and by an analytical model. The study reveals that the edge quality of the drilled microholes depends on the laser fluence reaching the rear exit of the hole and changes with the number of pulses applied after breakthrough. The minimum fluence that must reach the hole’s exit in order to obtain high-quality microholes in stainless steel was experimentally found to be 2.8 times the ablation threshold.

scholarly journals A Case of Facial Partial Unilateral Lentiginosis Treated with Low-Fluence 1,064 nm Q-Switched Neodymium-Doped Yttrium Aluminum Garnet Laser

2017 ◽  
Vol 9 (2) ◽  
pp. 30-34 ◽  
Author(s):  
En Hyung Kim
Keyword(s):  
Nd:Yag Laser ◽  
Standard Treatment ◽  
Yttrium Aluminum Garnet ◽  
Normal Skin ◽  
Patient Response ◽  
Yttrium Aluminum Garnet Laser ◽  
Selective Photothermolysis ◽  
Yttrium Aluminum ◽  
Postinflammatory Hyperpigmentation ◽  
Good Cosmetic

Partial unilateral lentiginosis (PUL) is an unusual pigmentary disorder characterized by numerous lentigines grouped within an area of normal skin. Although treatment is not necessary, many patients with facial PUL seek medical help for cosmetic reasons. There is no established standard treatment for PUL. Conventional lasers may cause postinflammatory hyperpigmentation because keratinocytes are injured during the process. Also, scarring, long downtime, and pain are important issues. A 19-year-old patient with facial PUL was successfully treated with low-fluence 1,064-nm Q-switched neodymium-doped yttrium aluminum garnet (QS Nd:YAG) laser. Although the exact mechanism by which low-fluence 1,064-nm QS Nd:YAG laser improves pigmentary lesions is unclear, the terms “subcellular selective photothermolysis” and “melanocyte apoptosis and replacement” have been proposed. If appropriate measures are taken to monitor patient response during and after the procedure, low-fluence 1,064-nm QS Nd:YAG laser may achieve good cosmetic results in the treatment of PUL with a very safe and effective profile.

Bundled hollow optical fibers for transmission of high-peak-power Q-switched Nd:YAG laser pulses

2006 ◽  
Vol 45 (27) ◽  
pp. 7174 ◽  
Author(s):  
Ozgur Yilmaz ◽  
Mitsunobu Miyagi ◽  
Yuji Matsuura
Keyword(s):  
Optical Fibers ◽  
Nd:Yag Laser ◽  
Peak Power ◽  
Laser Pulses ◽  
High Peak ◽  
High Peak Power

electromagnetic field at the particl e has to be computed numerically. An example of such a computation using a program based on [49] is given in Fig. 4. But not only doe s the Mie theory describe an enhancement of the laser intensity in the particles' near field, it also predicts that for certain values of the size parameter nd/X (d denoting the particle diameter, À the laser wavelength) the enhancement should be particularly efficient, resulting in a resonant intensity enhancement, the so-called "Mie-resonances". 3.2.2. Near-field induced substrate damage When inspecting contaminated samples by scanning electron microscopy (SEM) or atomic force microscopy (AFM ) after DLC using ns laser pulses, the consequences of the field enhancement process became obvious: all over the cleaned areas w e found substrate damages localized exactly at the former particle positions [35, 37-39]. These damages manifested as melting pools or even holes in the surface, typical examples can be seen in Fig. 5. The consequences for the laser cleaning process are obvious. The intensity enhancement reduces the maximum laser fluence that can be applied in the process. Usually in laser cleaning studies [19, 31 ] the laser fluence corresponding to the melting threshold of a bare surface is taken as the damage threshold fluence. Our experiments show clearly that this is an inadequate definition. Instead one must take into account the enhanced laser fluence underneath the particles, as it will be discussed in Section 4. Fro m the obtained AFM images we were able to analyse in detail the surface profile at the damaged sites. Here we found that for high field enhancement factors the silicon substrate was not only molten , but that some material was even ablated (see Sec. 4). The momentum transfer to the particles during the ablation process significantly contributes to the cleanin g process and hence local substrate ablation

2003 ◽  
pp. 327-330
Keyword(s):  
Laser Fluence ◽  
Near Field ◽  
Particle Diameter ◽  
Surface Profile ◽  
Field Enhancement ◽  
Damage Threshold ◽  
Laser Pulses ◽  
Laser Wavelength ◽  
Laser Cleaning ◽  
Intensity Enhancement

scholarly journals Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires

2021 ◽  
Vol 12 (1) ◽  
pp. e13-e13
Author(s):  
Hannaneh Ghadirian ◽  
Allahyar Geramy ◽  
Mohammad Ali Keshvad ◽  
Soolmaz Heidari ◽  
Nasim Chiniforush
Keyword(s):  
Laser Irradiation ◽  
Diode Laser ◽  
Nd:Yag Laser ◽  
Yttrium Aluminum Garnet ◽  
Testing Machine ◽  
Control Group ◽  
Friction Forces ◽  
X Ray ◽  
Custom Made ◽  
Ceramic Brackets

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd:YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires. Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd:YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd:YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P<0.05). Irradiation of diode and Nd:YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P>0.05). Conclusion: It appears that diode and Nd:YAG laser irradiation cannot significantly decrease the friction. Future studies are warranted on different laser types with variable exposure.

Preparation of fiber optics for the delivery of high-energy high-beam-quality Nd:YAG laser pulses

2000 ◽  
Vol 39 (33) ◽  
pp. 6136 ◽  
Author(s):  
Andreas Kuhn ◽  
Paul French ◽  
Duncan P. Hand ◽  
Ian J. Blewett ◽  
Mark Richmond ◽  
...  
Keyword(s):  
Fiber Optics ◽  
Nd:Yag Laser ◽  
Beam Quality ◽  
Laser Pulses ◽  
High Energy ◽  
High Beam ◽  
High Beam Quality

A STUDY OF FEMTOSECOND LASER POLISHING OF CVD NANOPOLYCRYSTALLINE DIAMOND FILMS

2021 ◽  
pp. 2150023
Author(s):  
YU-XIAO CUI ◽  
PING GUO ◽  
XUEMING ZHU ◽  
YAN-LING TIAN ◽  
DA-WEI ZHANG ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Fluence ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Laser Pulses ◽  
Promising Technique ◽  
Laser Polishing ◽  
Laser Fluences ◽  
Fs Laser ◽  
The Mean

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50[Formula: see text]MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7[Formula: see text]J/cm2, at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84[Formula: see text]nm to 31.88[Formula: see text]nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7[Formula: see text]J/cm2, large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

Experiment on Delivery of Megawatt Nd:YAG Laser Pulses by Large-Core Optical Fibers

2010 ◽  
Vol 37 (8) ◽  
pp. 1934-1938 ◽  
Author(s):  
赵兴海 Zhao Xinghai ◽  
胡建平 Hu Jianping ◽  
高杨 Gao Yang ◽  
马平 Ma Ping ◽  
谭刚 Tan Gang ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Nd:Yag Laser ◽  
Laser Pulses ◽  
Large Core
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