Prediction of Laser Induced Damage by Comparison of Laser Fluence Profile to Damage Spot Radius

AbstractInadvertent Er:YAG laser irradiation occurs in dentistry and may harm restorative materials in teeth. The aim of this in vitro study was to quantify Er:YAG laser-induced damage to a nanohybrid composite in simulated clinical scenarios for inadvertent direct and indirect (reflection) laser irradiation. The simulation was performed by varying the output energy (OE;direct˃indirect) reaching the specimen and the operating distance (OD;direct˂indirect). Composite specimens were irradiated by an Er:YAG laser. The ablation threshold was determined and clinically relevant parameters were applied (n = 6 for each OE/OD combination) for direct (OE: 570 mJ/OD: 10 mm, OE: 190 mJ/OD: 10 mm) and indirect irradiation (OE: 466 mJ/OD: 15 mm, OE: 57 mJ/OD: 15 mm, OE: 155 mJ/OD: 15 mm, OE: 19 mJ/OD: 15 mm). The extent of damage in the form of craters was evaluated using a laser scanning microscope (LSM) and a conventional light microscope (LM). The ablation threshold was determined to be 2.6 J/cm2. The crater diameter showed the highest value (LM: 1075 ± 18 µm/LSM: 1082 ± 17 µm) for indirect irradiation (reflectant:dental mirror) (OE: 466 mJ/OD: 15 mm). The crater depth showed the highest and comparable value for direct (OE: 570 mJ/OD: 10 mm; LSM: 89 ± 2 µm) and indirect irradiation (OE: 466 mJ/OD: 15 mm; LSM: 90 ± 4 µm). For each OD, the crater diameter, depth, and volume increased with higher laser fluence. However, the OD—and thus the laser spot diameter—also had an enlarging effect. Thus, indirect irradiation (reflectant:dental mirror) with only 47% of the laser fluence of direct irradiation led to a larger diameter and a comparable depth. The three-dimensional extent of the crater was large enough to cause roughening, which may lead to plaque accumulation and encourage caries, gingivitis, and periodontitis under clinical conditions. Clinicians should be aware that reflected irradiation can still create such craters.

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Dynamics of Ultrafast Laser Induced Damage in Single Crystal Ni-based Superalloy During Machining

MRS Proceedings ◽

10.1557/proc-980-0980-ii05-31 ◽

2006 ◽

Vol 980 ◽

Author(s):

Joel P. McDonald ◽

Shuwei Ma ◽

John A. Nees ◽

Tresa M. Pollock ◽

Steven M. Yalisove

Keyword(s):

Shock Wave ◽

Laser Fluence ◽

Ultrafast Laser ◽

Laser Exposure ◽

Mechanical Shock ◽

Incident Laser ◽

Machining Time ◽

Time Resolved ◽

Pump Probe ◽

Laser Induced Damage

AbstractPump-probe imaging of femtosecond pulsed laser ablation was performed to investigate the mechanical shock induced on an intermetallic superalloy CMSX-4 during femtosecond laser machining. Time resolved shadowgraphic images were collected of the shock wave produced in the air above the target following laser exposure (0-10.3 nanoseconds). The dimensions of the shock wave were measured as a function of delay time and laser fluence (1.27 J/cm2 - 62.8 J/cm2). Time-resolved shadowgraphic images of the ablation event will be presented, and the corresponding damage morphology as a function of incident laser fluence will be discussed.

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UHV-TEM studies of laser-induced damage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087471 ◽

1991 ◽

Vol 49 ◽

pp. 632-633

Author(s):

T.S. Savage ◽

R. Ai ◽

D. Dunn ◽

L.D. Marks

Keyword(s):

Surface Science ◽

Rapid Heating ◽

Local Heating ◽

Routine Practice ◽

Transmission Electron ◽

Northwestern University ◽

Laser Induced Damage ◽

Set Up ◽

Focusing Lens ◽

Diffusion Of Impurities

The use of lasers for surface annealing, heating and/or damage has become a routine practice in the study of materials. Lasers have been closely looked at as an annealing technique for silicon and other semiconductors. They allow for local heating from a beam which can be focused and tuned to different wavelengths for specific tasks. Pulsed dye lasers allow for short, quick bursts which can allow the sample to be rapidly heated and quenched. This short, rapid heating period may be important for cases where diffusion of impurities or dopants may not be desirable.At Northwestern University, a Candela SLL - 250 pulsed dye laser, with a maximum power of 1 Joule/pulse over 350 - 400 nanoseconds, has been set up in conjunction with a Hitachi UHV-H9000 transmission electron microscope. The laser beam is introduced into the surface science chamber through a series of mirrors, a focusing lens and a six inch quartz window.

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High Resolution Displacement of Functional Groups onto Fluorocarbon Resin Surface by Using ArF Excimer Laser

MRS Proceedings ◽

10.1557/proc-451-521 ◽

1996 ◽

Vol 451 ◽

Cited By ~ 1

Author(s):

T. Shimizu ◽

M. Murahara

Keyword(s):

Contact Angle ◽

High Resolution ◽

Laser Beam ◽

Thin Layer ◽

Functional Groups ◽

Excimer Laser ◽

Laser Fluence ◽

Large Area ◽

Three Solutions ◽

Arf Excimer Laser

ABSTRACTA Fluorocarbon resin surface was selectively modified by irradiation with a ArF laser beam through a thin layer of NaAlO2, B(OH)3, or H2O solution to give a hydrophilic property. As a result, with low fluence, the surface was most effectively modified with the NaAlO2 solution among the three solutions. However, the contact angle in this case changed by 10 degrees as the fluence changed only 1mJ/cm2. When modifying a large area of the surface, high resolution displacement could not be achieved because the laser beam was not uniform in displacing functional groups. Thus, the laser fluence was successfully made uniform by homogenizing the laser beam; the functional groups were replaced on the fluorocarbon resin surface with high resolution, which was successfully modified to be hydrophilic by distributing the laser fluence uniformly.

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