Nanosecond Time-Resolved Measurements of Hole Opening During Laser Micromachining of Aluminum Films

2012 ◽  
Author(s):  
David A. Willis ◽  
Mohammad Hendijanifard
Keyword(s):  
Shock Wave ◽  
Pulse Width ◽  
Laser Micromachining ◽  
Nitrogen Laser ◽  
Time Resolved ◽  
Recoil Pressure ◽  
Aluminum Films ◽  
High Fluences ◽  
Transmission Imaging ◽  
Opening Process

Laser micromachining of aluminum films on glass substrates is investigated using a time-resolved transmission imaging technique with nanosecond resolution. Micromachining is performed using a 7 ns pulse-width Nd:YAG laser operating at the 1064 nm wavelength for fluences ranging from 2.2 to 14.5 J/cm2. Transmission imaging uses a nitrogen laser-pumped dye laser with a 3 ns pulse-width and 500 nm wavelength. Images are taken from the back of the sample at various time delays with respect to the beginning of the ablation process, allowing the transient hole opening process to be observed and measured. Results show that for high fluences the holes begin opening during the laser pulse and that the major portion of the holes have opened within the first 50 ns of the process. The second stage of the process is slower and lasts between 100–200 ns. The rapid hole opening process can be attributed to melt expulsion due to recoil pressure on the surface of the melt pool rather than Marangoni flow. Recoil pressure may be due to vaporization at the free surface at low fluences and phase explosion (explosive liquid-vapor phase change) at higher fluences. Measurements of the transient shock wave position are used to estimate the pressure behind the shock wave and indicate pressures at high as 89 atm during ablation. The high pressure above the laser spot results in pressure on the molten surface, leading to expulsion of the molten pool in the radial direction.

Nanosecond Time-Resolved Measurements of Transient Hole Opening During Laser Micromachining of an Aluminum Film

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Mohammad Hendijanifard ◽  
David A. Willis
Keyword(s):  
Shock Wave ◽  
Phase Change ◽  
Pulse Width ◽  
Laser Micromachining ◽  
Aluminum Film ◽  
Dye Laser ◽  
Time Resolved ◽  
Recoil Pressure ◽  
Hole Area ◽  
Explosive Phase

Laser micromachining of an aluminum film on a glass substrate is investigated using a time-resolved transmission imaging technique with nanosecond resolution. Micromachining is performed using a 7 ns pulse-width Nd:YAG laser operating at the 1064 nm wavelength for fluences ranging from 2.2 to 14.5 J/cm2. A nitrogen laser-pumped dye laser with a 3 ns pulse-width and 500 nm wavelength is used as a light source for visualizing the transient hole area. The dye laser is incident on the free surface and a CCD camera behind the sample captures the transmitted light. Images are taken from the back of the sample at various time delays with respect to the beginning of the ablation process, allowing the transient hole area to be measured. For low fluences, the hole opening process is delayed long after the laser pulse and there is significant scatter in the data due to weak driving forces for hole opening. However, for fluences at and above 3.5 J/cm2, the starting time of the process converges to a limiting minimum value of 12 ns, independent of laser fluence. At these fluences, the rate of hole opening is rapid, with the major portion of the holes opened within 25 ns. The second stage of the process is slower and lasts between 100 and 200 ns. The rapid hole opening process at high fluences can be attributed to recoil pressure from explosive phase change. Measurements of the transient shock wave position using the imaging apparatus in shadowgraph mode are used to estimate the pressure behind the shock wave. Recoil pressure estimates indicate pressure values over 90 atm at the highest fluence, which decays rapidly with time due to expansion of the ablation plume. The recoil pressure for all fluences above 3.1 J/cm2 is higher than that required for recoil pressure driven flow due to the transition to explosive phase change above this fluence.

Modeling of Pressure Evolution During Nanosecond Laser Ablation of Metal Films

2009 ◽  
Author(s):  
Mohammad Hendijanifard ◽  
David A. Willis
Keyword(s):  
Shock Wave ◽  
Laser Ablation ◽  
Pulse Width ◽  
Metal Films ◽  
Normal Shock ◽  
Nanosecond Laser ◽  
Time Resolved ◽  
Aluminum Films ◽  
Nanosecond Laser Ablation ◽  
Fluid Properties

Nanosecond laser ablation is studied using a theoretical model combined with experimental data from laser ablation of metal films. The purpose of the research is to obtain the recoil pressure boundary condition resulting from explosive phase change. The ablation experiments are performed using a Nd:YAG laser of 1064 nm wavelength and 7 ns pulse width at full width half maximum. Three samples, 200 and 1000 nm aluminum films and 1000 nm nickel films, are used in the experiments. The transient shock wave positions are obtained by a time-resolved shadowgraph technique. A N2-laser pumped dye laser with 3 ns pulse width is used as an illumination source and is synchronized with the ablation laser to obtain the transient shock wave position with nanosecond resolution. The transient shock position is used in a model for finding the shock wave speed as well as the pressure, temperature, and velocity just behind the shock wave. A power law is used for fitting curves on the experimentally obtained shock wave position. Knowing the shock wave position, the normal shock equations are used to calculate the thermo-fluid properties behind the shock wave. The solutions are compared with the Taylor-Sedov solution for spherical shocks and the reason for the deviation is described. The thermo-fluid property results show similar trends for all tested samples. The results show that the Taylor-Sedov solution under-estimates the pressure behind the shock wave when compared to the normal shock results.

Time-Resolved, Laser-Induced Phase Transformation in Aluminum

1984 ◽  
Vol 35 ◽  
Author(s):  
S. Williamson ◽  
G. Mourou ◽  
J.C.M. Li
Keyword(s):  
Point Defect ◽  
Long Range ◽  
Rapid Heating ◽  
Range Order ◽  
Nucleation Theory ◽  
Long Range Order ◽  
Time Resolved ◽  
Aluminum Films ◽  
Thin Aluminum ◽  
Initial Nucleus

ABSTRACTThe technique of picosecond electron diffraction is used to time resolve the laser-induced melting of thin aluminum films. It is observed that under rapid heating conditions, the long range order of the lattice subsists for lattice temperatures well above the equilibrium point, indicative of superheating. This superheating can be verified by directly measuring the lattice temperature. The collapse time of the long range order is measured and found to vary from 20 ps to several nanoseconds according to the degree of superheating. Two interpretations of the delayed melting are offered, based on the conventional nucleation and point defect theories. While the nucleation theory provides an initial nucleus size and concentration for melting to occur, the point defect theory offers a possible explanation for how the nuclei are originally formed.

scholarly journals Fiber-Optic Time-Resolved Fluorescence Sensor for in Vitro Serotonin Determination

1993 ◽  
Vol 47 (5) ◽  
pp. 590-597 ◽  
Author(s):  
Stephane Mottin ◽  
Canh Tran-Minh ◽  
Pierre Laporte ◽  
Raymond Cespuglio ◽  
Michel Jouvet
Keyword(s):  
Chemical Sensor ◽  
Fiber Optic ◽  
Fiber Optic Sensor ◽  
Excitation Wavelength ◽  
Nitrogen Laser ◽  
Time Resolved ◽  
Temporal Effects ◽  
Starting Point

At pH 7 and with the excitation at wavelengths above 315 nm, previously unreported fluorescence of 5-HT (5-hydroxytryptamine) is observed. Two fluorescence bands were observed for 5-HT; the first emits at around 390 nm with an associated lifetime near 1 ns, and the other (well known) emits at 340 nm with an associated lifetime of 2.7 ns. With both static and time-resolved fluorescences, the spectral and temporal effects of the excitation wavelength were studied between 285 and 340 nm. With these basic spectroscopic properties as a starting point, a fiber-optic chemical sensor (FOCS) was developed in order to measure 5-HT with a single-fiber configuration, nitrogen laser excitation, and fast digitizing techniques. Temporal effects including fluorescence of the optical fiber were studied and compared with measurements both directly in cuvette and through the fiber-optic sensor. Less than thirty seconds are required for each measurement. A detection limit of 5-HT is reached in the range of 5 μM. Our system, with an improved sensitivity, could therefore be a possible and convenient “tool” for in vivo determination of 5-HT.

Early Dynamics of a Laser-induced Underwater Shock Wave

2021 ◽  
Author(s):  
Guihua Lai ◽  
Siyuan Geng ◽  
Hanwen Zheng ◽  
Zhifeng Yao ◽  
Qiang Zhong ◽  
...  
Keyword(s):  
Shock Wave ◽  
Numerical Method ◽  
Cavitation Bubble ◽  
Laser Energy ◽  
Optical Breakdown ◽  
Pulsed Laser ◽  
Underwater Shock Wave ◽  
Time Resolved ◽  
High Attenuation ◽  
Nanosecond Pulsed Laser

Abstract The objective of this paper is to observe and investigate the early evolution of the shock wave, induced by a nanosecond pulsed laser in still water. A numerical method is performed to calculate the propagation of the shock wave within 1µs, after optical breakdown, based on the Gilmore model and the Kirkwood-Bethe hypothesis. The input parameters of the numerical method include the laser pulse duration, the size of the plasma and the maximally extended cavitation bubble, which are measured utilizing a high time-resolved shadowgraph system. The calculation results are verified by shock wave observation experiments at the cavitation bubble expansion stage. The relative errors of the radiuses and the velocity of the shock wave front, reach the maximum value of 45% at 5 ns after breakdown and decrease to less than 20% within 20 ns. The high attenuation characteristics of the shock wave after the optical breakdown, are predicted by the numerical method. The quick time and space evolution of the shock wave are carefully analyzed. The normalized shock wave width is found to be independent of the laser energy and duration, and the energy partitions ratio is around 2.0 using the nanosecond pulsed laser.

Treatment of Leg and Face Veins with a Cryogen Spray, Variable Pulse Width 1064 nm Nd:Yag Laser—A Prospective Study of 47 Patients

2002 ◽  
Vol 19 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Cindy Y. Li ◽  
Sorin Eremia
Keyword(s):  
Prospective Study ◽  
Nd:Yag Laser ◽  
Pulse Width ◽  
Skin Type ◽  
Type I ◽  
High Fluences ◽  
Vein Segment ◽  
The Face ◽  
A Prospective Study ◽  
Reticular Veins

Objective: Throughout the 1990s, laser treatment of leg veins was a challenge. Newer, longer wavelength lasers capable of delivering high fluences with larger spot sizes with a variable pulse width have shown promising preliminary results. Experience with these lasers for treatment of facial telangiectasia and periorbital reticular veins is even more scant. To our knowledge this is the first prospective study to evaluate a variable pulse width, cryogen spray—equipped 1064 nm Nd:Yag laser for both the treatment of leg and face veins, including larger periorbital reticular veins. Materials and Methods: Forty-seven volunteers aged 32–67 years (30 with skin type I-V with leg telangiectasia and reticular veins, and 17 with skin type I-IV with face telangiectasia and reticular periorbital veins) were treated with the Nd:Yag laser. For leg vein patients, 2–3 sets of different leg veins were treated with a maximum of 3 treatments. Patients were examined 1 week after each treatment and at 1, 2, and 3 months after the last treatment. All face vein patients received 1 treatment and were examined at 1 month posttreatment. Treatment parameters for both leg and face veins varied with the size of vessels being treated. Pre- and posttreatment 35 mm photos were taken. Improvement was judged by 2 experienced physicians both visually on patients and by comparison of pre- and posttreatment photos. Results were graded as percent resolution in 5 groups: 0%, 0–25%, 25–50%, 50–75%, and 75–100%. Results: Twenty-three of 30 patients completed the leg vein segment of the study. A total of 41 leg vein sites were treated. Greater than 75% improvement was observed at 85% of the treated sites. Greater than 50% improvement was observed at 95% of the treated sites. Less than 25% improvement was observed at 5% of the treated sites. Seventeen of 17 patients completed the face vein segment of the study, and 32 sites were treated (24 cheeks, noses, and chin telangiectasia and 8 periorbital reticular veins). Greater than 75% improvement was observed at 97% of the treated sites. Greater than 50% improvement was observed at 100% of the treated sites. Notably, 100% of the facial reticular veins treated had essentially 100% resolution. Pain during treatment was variably perceived by patients, but was occasionally sufficient for patients to decline further treatment. Transient hemosiderin pigmentation, as seen with sclerotherapy, was common with larger vessels. Conclusion: The cryogen spray-equipped 1064 nm Nd: Yag laser was remarkably effective and safe for skin type I-V patients. Excellent results for leg veins, approaching sclerotherapy outcomes, were obtained for both 0.3–1.5 mm telangiectasia and larger 1.5–3.0 mm reticular veins. Furthermore, this 1064 Nd:Yag laser is also an outstanding tool for treatment of facial telangiectasia with little if any risk of purpura. For the first time we appear to have a safe and effective treatment for 1–2 mm periorbital reticular veins. The use of topical anesthesia may be needed for some patients.

Low Attenuation Shock Tube: Driving Mechanism and Diaphragm Characteristics

1971 ◽  
Vol 49 (15) ◽  
pp. 1982-1993 ◽  
Author(s):  
F. L. Curzon ◽  
M. G. R. Phillips
Keyword(s):  
Shock Wave ◽  
Simple Model ◽  
Shock Tube ◽  
Electric Shock ◽  
Strong Evidence ◽  
Room Temperature ◽  
Wave Motion ◽  
Driving Mechanism ◽  
Driver Gas ◽  
Opening Process

The properties of an electric shock tube fitted with a diaphragm are examined. The diaphragm opening process and its effect on the motion of the shock wave are studied. A simple model to account for the diaphragm opening time is given and critical comparisons of theory and results with other work are made.The model works well both for shock tubes employing room temperature driver gas and also for those using heated driver gas. Furthermore, there is strong evidence that the diaphragm opening process is responsible for the accelerating phase of the shock wave motion in both types of shock tube.

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

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.

Laser-excited immunofluorometric assay of prolactin, with use of antibodies coupled to lanthanide-labeled diethylenetriaminepentaacetic acid.

1986 ◽  
Vol 32 (7) ◽  
pp. 1323-1327 ◽  
Author(s):  
H Déchaud ◽  
R Bador ◽  
F Claustrat ◽  
C Desuzinges
Keyword(s):  
Plasma Sample ◽  
Solid Phase ◽  
Nitrogen Laser ◽  
Diethylenetriaminepentaacetic Acid ◽  
Time Resolved Fluorescence ◽  
Time Resolved ◽  
Step Procedure ◽  
Polystyrene Tube ◽  
Sandwich Type ◽  
One Step

Abstract We describe an immunofluorometric assay for prolactin based on lanthanide labeling of a monoclonal antibody and measuring time-resolved fluorescence. In this "sandwich"-type assay, the label (Eu3+) was bound to the second antibody by means of a simple, rapid method involving the anhydride of diethylenetriaminepentaacetic acid. To measure the photoluminescence of europium (or other lanthanides), we have developed a time-resolved fluorometer with a nitrogen laser as the pulsed excitation source. During the assay, the solid-phase antibody immobilized inside a polystyrene tube is incubated with the plasma sample and the second antibody in a one-step procedure. Results for 67 human plasmas correlated well (r = 0.98) with those by an immunoradiometric method.

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