Science method

Laser Ablation - Science method

Laser ablation is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough.
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I use Fujikura CT-30 cleaver for PCF cleaving to use for supercontinuum generation. Initially, it seems like working fine as I could get high coupling efficiency (70-80%) in the 3.2um core of PCF. However, after some time (several hours) I notice that coupling efficiency decreases drastically and when I inspect the PCF endface with an IRscope, I could see a bright shine on the PCF end facet, which is maybe an indication that the end face is damaged. Also, I want to mention that the setup is well protected from dust and there is no chance of dusting contaminating the fiber facet.
Please suggest what should be done to get an optimal cleave, shall I use a different cleaver (pls suggest one) or there are other things to consider.
Thanks
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Supercontinuum generation by short pulse with high power that lead to traction or fusion soliton.
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Why the values of the intensity ratio of doublet spectra of the laser-produced plasma spectrum differ from the theoretical value of the intensity ratio given in NIST data.
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It may be the result of line absorption in plasma.
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Can ultrafast lasers be used for carbon fiber ablation.
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Hello Melika
Lasers can process different types of materials, such as metals, semiconductors, polymers and composites. Usually, by using pulsed lasers (e.g., short and ultrashort pulses), laser micromachining via ablation (material removal) is possible. Then, you can perform laser-based materials processing such as drilling, marking, engraving, and surface texturing. I believe that for carbon fibers nanosecond, picosecond, and femtosecond lasers emitting radiation at the near Infrared or visible ranges would work properly. There are plenty of laser sources commercially available which are capable to do the job. When it comes to fast and ultrafast laser surface texturing, developments to control optical properties, biological behavior, wettability of several liquids, adhesion, and wear can be easily found in the literature.
From my point of view, there is always the need of finding the most profitable combination between the laser radiation and the material properties, accompanied to the fulfillment of the technical requirements and the cost and time associated with the process.
Good luck in your work !!!
Best regards !!!
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Hello, I have a doubt about nano fabrication in liquid, I would like to know when we use Femto second laser ablation of a solid target in a material, then we can choose able to see what patterns we have on the surface of solid, and also nano particles that are in the solution, generated during ablation process? In other words when we talk about fabrication do we mean making patterns or generating of nano collisions in liquid? Or does it just depend on what is the aim of project?
hope my question is clear.
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Dear Melika Afshar , you´re welcome.
Best!
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Hi,
I am planning to simulate nanosecond pulsed laser heating/ ablation on metal. Comsol or Lumerical, which would be the best for this simulation? Also, I would appreciate if anyone can suggest me a good tutorial on that. Thanks.
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Dear colleagues I have synthesized ZnO from Zn Plate using fiber laser using liquid laser ablation but it has shown no antibacterial activity
could anyone suggest how to solve such a problem?
Best Regards
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Dear Huda M.H many thanks for posting this very interesting technical question on RG. The antimicrobial activity of zinc oxide (ZnO) depends very much on the particle size. Antimicrobial activity is exhibited mainly by ZnO nanoparticles, whereas is is not pronounced when you have bulk ZnO material. For more information about this issue, please have a look at the following potentially useful review article:
Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism
Fortunately this review has been posted by the authors as public full text on RG so that you can freely download it as pdf file.
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
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Dear Colleagues......
How can we determine the ablation threshold of a material in liquid laser ablation?
many thanks
Huda
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Dear Huda M.H.,
generally you can use the same principles/methods for measuring the ablation threshold for ablation in a liquid than for ablation in air, but you must more carefully control the experimental constraints.
If you are using a leaser beam with a spatially Gaussian intensity distribution, then I would recommend to you the so-called D2-method that was published first by J.M. Liu in 1982, see
The essential idea would be that you first immerse your ssample in the liquid, adjust the sample surface in the laser focus plane and then irradiate the surface with a fixed number of laser pulses N (I assume here that you do not use a cw-laser) per spot, with all other parameters (such as pulse duration) being fixed - except the laser pulse energy: for each fresh sample spot, you are increasing the laser pulse energy (E), best by a fixed factor. If you chose the range of pulse energies in a good way, you are creating a series of separated ablation spots at the samüle surface. This spot series can then be evaluated e.g. with a good optical microscope, where you measure the diameter (D) of the ablation craters for the entire series.
If you then plot D2 vs. ln(E), you can determine from a least-squares-fit of the experimental data to a simple model of a Gaussian beam presented by J.M. Liu (see above) the Gaussian beam waist radius w0 and the ablation theshold energy Eth. That threshold value is valid for the value of N that you had selected (while w0 should not depend on N). Since the laser pulse energy and the fluence of a Gaussian beam are related to each other, you can easily calculate then also the ablation threshold fluence Fth for the given N.. Usually Fth(N) decreases for increasing N, an effect that is generally called "incubation". It may have different physical origins, depending on the irradiated material and laser...
This D2-method has the intrinsic advantage to evaluate w0 exactly ate the sample surface. But you must take care that the presence of the liquid does not disturb the measurement. For ultrashort laser pulses this may occur through the Kerr effect. Or it may disturbed by gas-bubbles created by the pulse and being present when the next laser pulse arrives to the scanario. So you may reduce the pulse repetition rate - or ideally use a single laser pulse. But then your samples should be quite smooth that you can easily see the ablation craters. Best make the least-squares-fit close to the ablation threshold since at high pulse energies/intensities the mentioned effects may significantly disturb.. Also it is beneficial to use a thin liquid layer above the surface only.
If you are using a closed liquid cell with windows for the laser radiation, then you should consider the Fresnel reflectivity of all interfaces in the beam path before reaching the sample, since these reflections reduce the amount of pulse energy reaching the liquid/sample interface. If you have no windows, then you may just consider the Fresnel reflectivity of the air/liquid interface. An example for a liquid confining cell is given here
Hope it helps..
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I am the manager of a laser ablation lab at Cornell and we have an ESI NWR193HE that was installed Aug 2020. Its only been truly operational for about a year but we are experiencing a high loss of laser energy over time. Fluences of 5-10 J/cm2 are costing more and more of the laser's energy output. At about 6 months, we were already at half of the installation energy output, now at a year we're at a quarter. The service engineer has quoted us for some very expensive optic repairs but has anyone else experienced such a high loss this quickly before?
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Sometimes, backreflection or emission from a sample may damage the optics inside the laser resulting in a power drop. Use of an optical isolator is usually recommended to prevent backreflection into the laser.
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I want to generate second harmonic using the long-wavelength (1600nm) part of the supercontinuum as pump. How to decide on choosing the right focal length lens for SHG. I am using 10mm-long MgO-PPLN. The average power at the output of supercontinuum is ~100mw and ~40mw for SHG (after long-pass dichroic mirror). Since the temporal profile of the signal after SC is not known (specifically for the 1600nm part ), is it suitable to treat that signal as continuous-wave for SHG pump. For CW pump, the literature suggests that the ratio of crystal length to the confocal parameter (2*Rayleigh range) should be 2.84 for optimal SHG. From where we may calculate the right focal length of the lens to focus light into the SHG crystal.
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you welcome Abbas N..
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Hi I am trying to synthesize quantum dots for the fabrication of electrodes for HER. I have metal oxide power so conventionally people use plates as target for production of Quantum Dots. So is it possible to use powder as target precurosor for synthesis of Quantum dots?
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Dear Shahbaz Ahmad,
Yes, of course, it is possible to synthesis of TMO QDs using TMO powder as target precurosor.
I hope that my article paper have been helped you.
Modified top-down approach for synthesis of molybdenum oxide quantum dots: sonication induced chemical etching of thin films
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I synthesized gold nanoparticles by pulsed laser ablation in different ph solutions. At acids 1 and 3, it didn't show any absorbance peak whereas at pH 7 and 11 it does have absorbance peak. However most of the chemical methods that produces gold nanoparticles mention that acid can resulting in formation of nanoparticles.
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Dear Ainin
Gold NPs solution should give an absorption band at about 500nm, however, the spectrum depends on many factors such as pH, size of NPs and etc. Please check the following paper for more information.
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I have generated an octave-spanning supercontinuum (750-1700nm) using 140fs pulses. I want to frequency double longer wavelength (1600nm) using PPLN crystal. Since, I don't know what's the pulse duration/shape, peak power, or energy in that specific bandwidth (around 1600nm), how should I choose SHG crystal (PPLN) for SHG. Specifically, how to determine crystal length and acceptance bandwidth for optimal SHG at 800nm.
Thanks in advance.
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Dear Prof. Walid Tawfik , I want to convert 1600nm to 800nm using SHG crystal.
Thanks for the link you have provided.
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I want to produce an N-doped Carbon using GO or AC with Urea as a precursor. But I have a limited technology such as CVD, laser ablation, etc. Do you have any suggestion?
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Usually when we preparation NPs from metals (Tio2, Ag) by laser ablation in Liquid, the concentration of NPS in liquid is unknown, my Question how can measuring this concentration for NPS in the same solution without evaporate this solution
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Thank you Dr. Vedhanayagam Mohan
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i am prepare ZnO/Au Nanoparticals by laser ablation and mixing together, How can i know the core-shell theory has been ِAchievied from the result?
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no u cant get info without doing tem, as tem/ fesem is used to understand structural morphology wherein xrd /uv vis is used to characterize its chemical composition
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Hi,
I am working on a MD problem to simulate the laser ablation. I know that people calculate the highest temperature in the material through the solution of heat conduction equation FEA simulations etc., and apply the calculated temperature directly in MD simulations. I am wondering if there is a direct approach or any other method to do this directly in MD?
Many Thanks,
Vivek
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This is a very interesting problem, which is typically too complex to solve by the electromagnetic or wave equation approach.
Unless you are dealing with photoablation, which typically happens with high energy photons in the UV or shorter wavelength spectrum in which laser light overcomes electronic transition and directly dissociates atoms and molecules, most laser ablation as we know it undergoes photothermal/photoacoustical/thermomechanical processes. There are however extreme cases with much complexity, such as in the case of extremely high laser irradiance > 10^12 W/cm2 where nonlinear dynamics kick in, causing optical breakdown and plasma formation - this typically happens with ultrashort laser pulses.....
For 'typical' laser ablation, I suggest starting with a Monte Carlo model, simulating laser irradiation as photon transport/migration into the material. Assuming you know the optical properties of the material, you would be able to determine the photon distribution, optical absorption, and loss (reflectance and transmittance). Time resolved optical absorption produces the source term for the heat conduction equation with which you use to calculate the temporal temperature changes. This photothermal process may or may not result in ablation. If it is below the ablation threshold, the time-temperature relation of laser interaction with the material may result in changes in its chemical or structural integrity. If it is above the ablation threshold, where local temperature rise and gradient are directly correlated to (and the source term for) mechanical stress or pressure induced within the material, one could calculate the acoustic pressure and recoil stress that may overcome the molecular bonds resulting in vaporization and dissociation (hence ablation and change in boundary condition). For short pulsed lasers operating in stress confinement, an approach to understanding this thermodynamic process may be modeled using the Grüneisen Parameter. Below are some references:
For references in Monte Carlo model, work by Jacques and Wang is well known:
Pfefer et al have studied the Monte Carlo and heat diffusion approach extensively:
Photoacoustical process/Thermomechanical ablation:
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When analyzing geoloical samples (element or isotope composition) with ICP-MS which type of laser ablation system would provide better result - nanosecond laser (193//213 nm) or femtosecond one?
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Hi Dany
We have never found a "finer" aerosol formed after LA in silicates. In fact Reto observed even more particles > 20 nm with 795 nm and 265 nm fs LA in silicate and zircon (Glaus et al. Spectrochimica Acta Part B 65 (2010) 812–822).
For such insulators, there is apparently sufficiently low heat dissipation on the ns time scale to avoid a deep melt and the corresponding splashed drops.
Best regards
Bodo
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We have been attempting to sinter conductive silver ink onto a glass substrate using laser ablation. So we want to know if there are any pre-treatment methods which can enhance the quality of the sintered lines or help in increasing the efficiency of the sintering process.
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i think you can use graphite to absorb laser by coating it on the silver paste. You can use a semiconductor layer having a bandgap smaller than the photon energy of the laser.
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Is there a reason why nobody performed Doppler cooling of Y III (Y^{2+}) ions? It seems that transitions are similar to those in Ca+ ions (three level system). Y III ions could be produced by laser ablation, which was the method used for getting optical spectra of these ions in past.
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Sounds like an interesting idea. I did preliminary work on how to use precision measurements of the ground state in singly and doubly ionised ions in traps to obtain high accuracy values of the hyperfine anomaly over 20 years ago. The idea was to test it for stable isotopes first and then try to implement it for unstable isotopes. There were some interest in G. Werths group, but they could not cool and analyse their test ion sufficiently.
Just to demonstrate that it is possible with precise values would be nice. Even if Y is not the optimal choice.
Send me an email jonas.persson@ntnu.no for further discussions.
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When nano particles used for strengthening or to improve some property it needs to dispersion in the matrix phase by ultrasonic bath or tip.
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The technique is called MAPLE - Matrix-Assisted Pulsed Laser evaporation. First, a polymer (or nanoparticles in your case) has to be dissolved (suspended) in a proper solvent. Then, the solution (suspension) made freeze up in liquid nitrogen. The obtained solid is used for laser ablation (evaporation) and vapor deposition.
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I analyzed high temperature hydrothermal pyrites for trace elements using a XSeries 2 ICP-MS coupled to a Laser Ablation system. I carried on the measurements using a beam diameter of 75 μm. Once I got my data and corrected using standards (GSC, GSD and GSE) elements that have ~>10,000 ppm concentration are around 2 orders of magnitude higher than expected (compared to EMPA measurements on the same crystals). Is there a way of correcting the machine over-range or saturation?
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Hi Irene,
You need a Natural pyrite standard for calibration.
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What will be the ablation temperature of Cu and Al. If we estimate it from ClT+Ce'T2= Enthalpy of evaporation ( Where Cl- specific heat of lattice and Ce'- specific heat constant for electron) for Cu it is around 10,000 K and for Al it is around 13,000 K is it correct?
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Your question is not very clear. If you want to estimate the temperature of the plasma just after the evaporation, this value is too low. The laser provide a very high power density. Part of this density is lost by thermal conductivity in the metal. This is not very important, because in the ns scale diffusion is too small. Part of the energy is used to evaporate the surface, which is relevant but not very high. The most important contribution is to produce and heat the plasma. In my old calculation I have estimated as early time temperature, values above 60000 K.
The plasma formed than cools down by expansion reaching temperatures around 10000 K. For higher temperature (at the beginning of the ablation) you cannot measure the spectrum because the continuum is too strong. You start to measure the spectra when the plasma reaches temperature around 5000-20000 K (depending on the plasma composition and environment pressure), when the electron density is decreased.
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I am planning to perform a laser ablation experiment on Ar diffused quartz in different depths, creating free Ar molecules which I need to capture instantaneously using a vaccum pump. But cant understand how should I design the experiment, and how much power the vaccum pump should have. Would really appreciate if I can get some suggestion.
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Please also take in account that all atoms including Ar may form clasters being ablated under very high vacuum conditions. So your mass spectrometer residual gas analyser should have adequate mass range to detect the majority of clasters of various mass formed.
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Hi there,
Do you know how to measure longitudinal and transverse modes in lasers? I need to know the cutting edge and experimental techniques related to this subject.
Bests,
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Dear Sourav,
Thank you for your answer. Could you please explain more about S2 measurement technique ?
Thanks,
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Stopping radius of plasma
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For stopping the plasma expansion, there must be some force. In vacuum only the collision of plasma with neutral can stop the free expansion of plasma. The presence of some buffer gas can confine the plasma. In this case stopping radius will be decided by the pressure of the neutral buffer gas. In the absence of magnetic field and buffer gas plasma can diffuse even up to infinity. So in the absence of magnetic field only buffer gas can stop the plasma.
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I would like to know who is actively working on this topic. I would appreciate some feedback on the type of lasers that is being used for that, materials and applications.
Thank you so much.
Best regards
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You can check our website for multiple publications on LAL and the applications of those nanoparticles..
There are reprints available on RG also.
Best Regards
Venugopal Rao Soma
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Does anyone could tell me which kind of features should I consider between the techniques Laser-Induced Breakdown Spectroscopy and Laser Ablation Inductively Coupled Plasma Mass Spectrometry to buy an instrument that will be used in geological samples for a geochemistry fingerprint focused research?
Both use Laser Ablation for particle generation so the sample preparation step is minimal but I would like to know about the instrument and maintance costs (if somebody has a shallow idea about it), the detection limits and the advantages that have one over the other.
I deeply appreciate your help in advance.
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Dear Cristhian
I agree with Prof. Baig and Dr. Marijn. LA-ICP-MS system as well as its maintainance is costly. It has been proved that LIBS works better even for the geological sample and is faster than the LA-ICP-MS. Finaly you have to decide keeping all the points in your mind in the present situation.
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I am doing research on tin and tin oxide nanoparticles using laser ablation method. Using Nd:YAG  laser in visible range (532nm) .By increasing the energy  i have observed the  decrease in the ratio of number of oxides. What might be the reason?The sample exposure time is constant/
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@ Xxx Sedao : No, gas shielding alone won't do you any good with this problem as I explained earlier. The oxygen comes form the dissociation of SnO2 at high temperatures, so you create the oxygen by yourself. Hence, there will be oxygen around even if you work in an inert atmosphere.
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How can be obtainable nanoparticles colloid from graphene-oxide by means of laser ablation and which are liquids types will be suitable for this preparation ?
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Dear Mohammed S. Mohmoud,
I am very pleasures for this reply and helpful.
Nd-yag pulsing laser
1640 nm
yes it immersed, the layer water no more than 1.5 cm
1 j energy in nanosecond duration range of duration
regards
Raad
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I’m interested in deposition condition of Li2O. Im assuming there is a non linear transfer from target to substrate, no? Furthermore im interested in finding suppliers for Li2O sputtering targets as well as sinter conditions for fabrication of the target on my own.
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Nice idea with your paper. Getting the right amount of Li into you films has often been a little "hand-wavy" in the literature (mostly just put in 15 wt% and hope for the best!) although this works pretty well for some systems, your paper points out that this can certainly be optimised better and this also gives you some more control than having to remake lots targets. I was slightly suprised by the number of pulsed given to Li2O (I'd have thought this would ave given you too much Li content but each PLD system is different and I see you substrate - target distance is significantly greater than ours and also keeping the temperature constant and perhaps relatively high for Li/Li2O, so maybe these will both play a role.
Yes, lithium certainly goes wandering as it seems to be highly scattered from the background gas so we when you optimise you background oxygen for your cathode material, this may not (probably is not) this ideal for Li2O, or the two combined. Target preparation is a big factor for us, trying to ensure truly intimate mixing of the Li2O (this keeps any Li2O particles in the target smaller and therefore the droplets smaller).
We get around this issue or varying Li transfer by making a lot of targets, varying the relative composition of the Li2O vs cathode. When we change cathodes, we also need to vary the Li2O content - e.g. when moving from spinel to layered materials (similar cations but different ratios, with different oxygen content and different cation transfer ratio)
Empirically you can get a feel for the how much lithium does scatter by looking at the plume. When you increase the oxygen pressure the angle the plume makes with respect to the target increases more rapidly than targets which have constituent cations of similar mass.
Looks like we have a bit to talk about so if you ever want to reach out to me directly, please do. Looks like Prof Tarancón and I were at Imperial College at the same time a few years back!
Thanks,
Joe
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I coated polymerized PDMS with a 50 nm layer of Al in an evaporator and got a satisfactory thin layer coverage, but then when using a 532 nm layer on it, it seems to make holes on it (powers between 22 mW and 0.2 mW), and when water is present it overheats it even at very low laser powers. Any idea of why?
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Hi Julia, I agree with Yariv. With a layer of Al on PDMS, the laser photons are collected and turned into heat. As your Al layer is thin, the thermal effect gets accumulated rather than dissipated, so at some point a crater is formed due to melting or most likely evaporation. What is the size of the laser spot on your sample? Without Al, PDMS is transparent to 532 nm laser light, photons pass through the PDMS without heating.
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I'm looking for a polymer (or even a type of tape) that can be used with high energy lasers in photoacoustic experiments.
The material must be able to repeatedly be exposed to 500 mJ/cm^2 from a nanosecond (5 nanoseconds) or picosecond laser pulse (8 picoseconds) without burning AND it must have favorable acoustic properties (an acoustic impedance close-ish to water at 1.5 MRayls) AND it must be optically transparent in the range from 400-700 nm.
Is there anything even remotely close to being able to handle these types of energies/powers in a polymer form or would it all have to be glass?
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I think Cyclic Olefin Copolymer (COC) is good option
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I am preparing gold nano particles by laser ablation with water as medium. The wavelength of laser is IR range.But water absorb IR wavelength. So I like to know the effect of IR absorption by water at the time of ablation. Whether it will effect the ablation process?
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good answer by Aparna
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I am preparing gold nano particles by laser ablation method. the medium is water. I have a genuine doubts how the ablation takes place for gold even though it has 99 % reflectivity. I want to know about the physics behind it.
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Dear Pradeep
You have to ask yourself the gold is 99% reflective at which wavelength?
what is the wavelength of the used laser device? because the reflectance of Au drops to less than 40%  below 500nm. In addition, the reflectance depends on the angel of incident radiation and the surface of the particles.
Please refer to the next paper.
Regards, 
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Can we calculate the threshold energy in the field of laser ablation of gold nanoparticles ?
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Thanks a lot.
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Which impurities are present in stainless steel SS 304?
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Hello Saifullah,
To determine the elements or impurities in your sample, it is necessary to have the data in order to enter it in an identification software.
I recommend you compare the position of your peaks with the NIST database.
If you are interested, I could also send you an elementary identification software that we have developed in our group for the LIBS technique
regards
Luis
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Why  CW laser is not enough to production nanoparticles from metals or semiconductors as ablation method ?
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External field-assisted laser ablation in liquid: An efficient strategy for nanocrystal synthesis and nanostructure assembly
Author links open overlay panelJ.XiaoP.LiuC.X.WangG.W.Yang
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Actually i am working on LIBS..And want to study Plasma parameters..
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LIBS is a spectroscopic technique capable of doing many tasks. As already stated in the previous answers, it can measure plasma temperature and electron density. They can give a good characterization figures of the plasma. This plasma (LIBS) can be used to perform the direct chemical characterization of solid samples without prior sample preparation. LIBS can also be used for nano-material preparation under liquid to be an environmentally friend preparation procedure. LIBS has many other applications in science and technology.
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What are the suitable liquid to immersed in it, the Si or. Sio2 or Na2SiO3 to production si-nanoparticles by mean of laser ablation? 
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Dear professor Muhammad Aslam, 
I am looking for more than water another liquid in order to do comparison.
thank for this nice and usful reply.
regard
Raad
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I would to obtaine the mental nanoparticlesWhat are the suitable liquid to immersed the cuo or cu2o to production cu-nanoparticles by mean of laser ablation?
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Dear dr.Raad
Have a nice time and good day
   All what has said above is right. There have been many literatures which reported that distilled water is the  suitable solvent for synthesis of the cupper nanoparticles  using pulsed laser ablation .
Regards
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comparsion to other methods of productions nanoparticles , is the laser ablation the most methods to smallest nanoparticles obtainable and why?
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Professor 
Thank so much
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as long as, how can prevent the aggregation the metal nano particles which are prepared by laser ablation ?
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You'll find something on the Bredig method in here (slides 34 onwards)
February 18th, 2016 Metal colloids - their preparation, application and characterization
Much of the metal is wasted and sediments out even with appropriate stabilizers (e.g. optimum phosphate concentration) in solution. A bottom-up chemical reaction is much more efficient and effective at preserving metal concentration.  On aggregation take a look at:
Nov 11th, 2008. Dispersion and nanotechnology  http://tinyurl.com/hpywsge
November 3rd, 2015 Adhesion and cohesion  http://tinyurl.com/zwb2wlh
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Are you working with preparation nanoparticles Or any thing more
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Under the term "ablation" (from the Latin "ablatio" - withdrawal,
elimination) in the physical literature is understood to mean the aggregate
complex physico-chemical processes, the result of which is removal of a substance from the surface or from the volume of a solid.One of the prevailing mechanisms of laser ablation is the majority researchers consider thermal, described in the framework of the thermal model.
Анисимов С.И., Лукьянчук Б.С. Избранные задачи теории лазерной
абляции // Успехи физических наук. 2002. Т. 172. № 3. С. 301–333.
See English translation
Best regards.
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We are working in preparation of core-shell (Ag@Au) collide by laser ablation in liquid. if Variation of thickness of shell(change in laser pulses) , are there any change in shape or width or position of Absorption peak ?? that can enable me to control shell thickness?
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Dear prof. Ghaleb
The article on the link blow contains trial for estimating the function of shell thickness Vs. peak energy shift using the Gaussian-Lorentzian mixed function.   
Best regards
"Enhanced Electronic Properties of Pt@Ag Heterostructured Nanoparticles"
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I have prepared nanoparticles using laser ablation method.I have shined  Nd: YAG laser (532nm) for 40 minutes and used different liquids(acetone,ethanol and methanol) at 30 and 60 mJ laser energy. My SEM result shows that with the increase of laser energy the particles size increases.  My Uv absorbance result shows blue shift with the increase of energy in case of ethanol and acetone. I am attaching my results.Kindly let me know if i am not analyzing it properly...Ethanol and acetone respectively
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Dear, one reason of ted shift is the Doppler effect.
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I have some semi-finished high-efficiency solar cells(PERC), for no local aluminum back contact after laser ablation. I want to removal the local SiO2 at the ablation area which maybe produce from being exposed to the air for long time. Hydrofluoric acid is a ideal selection, but it also etch the SiNx layer. So are there any other way for this selective etching?
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I support Markus' suggestion to try a very short HF dip.  The SiO2 from air exposure will be very thin compared to your SiNx.  You can use HF:H2O 1:10 or even more dilute.  If you have an ellipsometer, you can experiment with a silicon wafer exposed to air to verify SiO2 removal.
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I have prepared nanoparticle in de-ionized water using laser ablation at 180 mJ laser energy...i calculated band gap as 4.26 eV using tauc plot and kept my sample in liquid for and after 15 days again i go for UV absorption spectroscopy and my Tauc plot showed that two band gaps appears one at 3.41 eV and other at 4.25. What might be the reason? I´m attaching my result.
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Dear Collegue,
The curve (with this abrupt jump) seems to be due to an automathic change of scale in the electronic of your apparatous not from your sample.
Best regards
Pedro
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Hello there,
I've been working on fs laser processing on the surface of transparent materials, i.e. BK7, sodalime glass slide, polymers such as PMMA. I am trying to optimize laser process (given that pulse duration is 400fs and wavelength is 1030nm) so that after laser ablation (trenching, grooving, free form cavities) the surface roughness remains as small as possible (ideally still transparent).
I can achieve some 500nm Ra after laser machining myself. Anyone here doing better or knows how to do it better than that?
Cheers
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You can try a laser polish after ablation for glasses with longer pulses. There is some literature about this. The pulse duration depends on how much topology you would like to be flattened. Probably ns for flattening shallow topography, longer for higher. Be aware of strain induced by this.
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Hi,
I am working in ultrafast laser tissue ablation area. I feel it's difficult to find the laser focus in the tissue surface. Can anyone suggest me a technique to overcome this issue? I can't use the normal laser focusing method for material processing.
Syam
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Do you have sample geometry issue? If you work on tissue, I imagine the samples are somewhat freeform? A sample stretcher, clamp, or a jig could help you to set your samples to a prefixed form, then you will not have problems with finding focal plane each time you ablate a new sample.
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Laser ablation (LA) is is a less known and few employed procedure to accomplish hypertermic necrosis of liver tumors. LA was described for the first time by Bown in 1983. A main advantage of LA is that laser light can be delivered precisely and predictably into any location of the liver without affecting surrounding tissue. The light is transmitted from the source to the patient through flexible optic fibres. In the technique used by us, very thin bare optical fibers, measuring 300 mµ in diameter and with flat tips are inserted through a 21-gauge needle.
Nodules hard to treat because of:
1. position
a) high risk location
-       adjacent large vessels: vena cava, first or second branch of the portal vein, the base of hepatic vein
-       adjacent to extrahepatic organs: gallbladder, gastrointestinal tract
b) difficult-to-reach location
-       I segment or liver dome
-       behind large vessels
-       behind TIPS
According to Teratani, nodules located less than 5mm from large vessels or extrahepatic organs were classified as high-risk location nodules. (Teratani T, Yoshida H, Shiina S, Obi S, Sato S, Tateishi R, Mine N, Kondo Y, Kawabe T, Omata M. Radiofrequency ablation for hepatocellular carcinoma in so-called high-risk locations. Hepatology. 2006 May;43(5):1101-8.) Therefore nodules adjacent to a first or second branch of the portal vein, the base of hepatic veins, or the inferior vena cava, while nodules adjacent to extrahepatic organs were defined as those located less than 5 mm from the heart, lung, gallbladder,right kidney, or gastrointestinal tract.
2. size
3. multifocality
Characteristics of laser ablation that favours this technique to treat HCC nodule located in difficult sites are:
-       the use of thin needles;
-       very precise deliver of energy;
-       greatest flexibility;
-       no heat sink effect.
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I would say no.
Laser is time consuming, heating is slow (so there should be a heat-sink effect), the need for multiple needle positionings increase the risk for bleeding complications, the litterature is very scarce and the technique is still generally regarded as inferior to RF and microwave ablation. With the addition of IRE and the use of percutaneous (85%) and laparoscopic (15%) approach any small (<30mm) lesion in the liver can be treated effectively. Especially with the use of computer assisted guidence techniques (ultrasound with ct/mr fusion and ct with computer navigation tools (CAS))
The percentage is our centres distribution of access routes.
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We work in Dyes solution,we need to enhanced optical properties by make laser ablation of  Ag in this dyes solution.
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Yes you can but i suggest to do that in two directions the first one produce the Ag particles in this solution directly, the second to produce the Ag particles in alternative liguid like distil water and then mixed with your solution .Make comparison between these two solutions and check the structure variations.Also you can study the effect of different pulses, laser energy , and spot size on the final solution and the specifications of Ag particles.
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We work  by laser ablation in liquids ,we need to add nano collide to Rhodamine dyes ,Are there any effects on optical properties.
Are there any papers ?
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Dear Dr. Ahmed Saeed Hassanien ,
Thank you very much for a very good Explain,If there are any Reference or papers in this field.
Best Regards
Ghaleb 
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Hello experts,
I've tried to cut a project using SUS304 2B, but unfortunately the dross formation is rather critical and the dross formation. I've increase the focus distance but the result almost the same.
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Hello Dr Yurevich,
My mistake, forgot to attach information on the processing parameters.
Material : SUS304 2B
Thickness : 3mm
Laser type : CO2
Operation mode : CW
Laser power : 2800 W
Cutting speed : 1000mm/min
Assist gas type : N2
Gas pressure : 6.5 bar
Nozzle gap : 0.5mm
Ive tried using higher pressure assisted gas and the problem solved. Thank for your advice.
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1.) As far I know that the shock wave mismatching can be avoided with the polished surface during laser ablation and 2.) to remove surface defects like pits, nicks, lines and scratches in order to avoid surface fatigue crack initiation.
Is there any more reasons? I feel that there are some more inputs.., 
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Hello
I'd like to measure laser ablation plasma using LP(Langmuir Probe).
Then, the LP's theory is based on Maxwell distribution.
However, some kind of laser ablation plasmas are not the distribution.
I have seen some papers about measurement of the parameters of the plasma using LP.
I'm wondering about the correctness of the results of these papers.
Please advise for this question.
(and please introduce any reference documents  if you know)
Thanks.
Yuki Nakamura
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I'm amazed that none of the other answers have pointed this out, but here goes. A Langmuir probe can indeed be used as a diagnostic for certain types of plasmas, but it cannot be used for a typical laser-produced plasma.
Langmuir probes must be immersed in a plasma long enough to make voltage measurements etc. Therefore the desired plasma must:
  • Be in "steady state", i.e. slowly changing over timescales of at least a second or so
  • Have a large spatial extent, typically of several centimetres
  • Have low mass and energy densities, so typically not much more than atmospheric pressures and temperatures below hundreds of electronvolts
Laser-produced plasmas typically meet none of the above conditions. Practical laser ablation happens with short pulses (nanoseconds or shorted), focused to spots millimetres in diameter. A plasma produced in this way is far too short-lived and rapidly expanding to get a measurement with a Langmuir probe. Even a CW industrial cutting laser produces turbulent, rapidly recombining plasma with steep temperature and density gradients. Making measurements on it with a Langmuir probe is out of the question.
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I am investigating laser ablation in water with TiO2 nanoparticles, Usually I get a homogeneous blue colour afterwards, as expected. But sometimes the particles turn grey and aggregate compeltely at the bottom of he suspension. Has anybody experienced something similar?
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Thanks a lot, Sir. This is very helpful to me.
Do you think there are problems for the application in solar cells after aggregation?
Actually I have also performed SEM measurements and did not find any differences.
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 I am doing Research on tin and tin oxide nanoparticles using laser ablation method in different liquids. I have varied the energy and fixed the time and wavelength. The XRD result shows different planes appear when i increased energy from 30 mJ to 60 mJ. The intensity is also varying. My EDX result shows that oxide ratio increases and tin ratio decreases with the increase of laser energy. However my XRD result shows opposite relation. I am uploading my result for samples prepared in ethanol....Please help me in understanding this result
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Maybe the difference is caused by different origin of EDS and XRD signal? If your particles are not crystalline, they will appear in EDS but not in XRD. But it could be also because of small size of the particles, interferring with your results (both XRD and EDS could be problematic for non-experienced user due to large interaction voluem in EDS and strong background in XRD)...
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I am doing research on tin and tin-oxide nanoparticle using laser ablation method and used de-ionized water, acetone, ethanol and methanol as liquid media. I have varied the energy from 60 to 240 mJ for de-ionized water however for other liquid varied it from 30 to 60mJ. The oxidation rate increases with the decreases in energy when liquid was de-ionized water whereas for other liquid its opposite occurs. Why these liquid behaving differently so?
In two different research paper i have studied that that there is a threshold of laser flunece after which laser interact more with the liquid which causes an increase in oxidation rate.
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Dear Tanzeeha Jafari,
In my opinion, you have two main points related to this subject. First, your energy distribution profile is nearly Gaussian, so the energy distribution is not homogeneous in the area affected by the laser radiation. Second, you need to understand better the properties of your liquids. Certainly, the energy required to break the bonds is different depending on the liquid. The work function changes. I think that at least these two factors influence the variation on oxidation rate.
I hope you can find it out.
Best regards,
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I am using laser ablation method to prepare tin and tin oxide nanoparticles. I have varied liquid media and laser energy. For de-ionized water I have observe a  decrease in tin oxide ratio with an increase in tin ratio by increasing laser energy...But for acetone, ethanol and methanol its opposite is observed. For other media's it can be due to threshold fluence above which the laser interact more with liquid ..can the same reason valid for de-ionized water??? 
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What do you mean by Preferential ablation???My material is Pure Tin
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I am having splashing problem during my PLAL experiment, how I can reduce it?
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Dear,
The radiation can be directed at a particular angle of Brewster angle. If inclination is not feasible, a simple coverage should be applied with a dedicated opening where laser pulse can enter.
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I have used laser ablation method to prepare tin oxide nanoparticle. The UV-VIs absorbance spectrum show decay in absorbance concentration when i have changed energy from 60mJ to 180mJ 
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Hi I have started working on PLAL .. Do you know how to reduce the splashing problem during the ablation process??
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I am doing research on tin and tin oxide nanoparticles using laser ablation method.I have varied the liquid media from de-ionized water to acetone ,methanol and ethanol.The all the characterization results shows minimum oxide produced in case of ethanol compare to other......I have read somewhere that ethanol particles form a shell around the target material and stop its reaction with oxide....why this not happened in acetone and methanol?? Need your serious help
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See interaction of ethanol with the surface tin and tin oxide in the attached file.
Best regards.
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 I have prepare nanoparticles using laser ablation in liquid media.Varied energy from 60 to 180 mJ.I have actually randomly selected a sample prepared at 180mJ and than check the absorbance after 15 days....The absorbance increased but band gap decreased. What does It show??? the decay in band gap surely means agglomeration of particles but how the absorbance increased
Please help me with this.....
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I agree with Ravi Kishore comment that this could be due to increased scattering rather than increased absorbance (or a combination of both).
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I have used laser ablation method to prepare colloidal metal nanoparticles in different media, I need to know that information is obtained from the FTIR spectra, and the derivate of FTIR spectra?  I could see changes in these spectra when changing medium, but these results can not be interpreted.
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Changing medium obviously changing the surface morphology as well as criminality which may be the probable change of your spectra. 
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Is it possible that temperature of a solid with vaporization temperature of 500 C may shoot up to 1000 C when subjected to a laser?
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Yes, it is vaporization temperature.
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i want to simulate nano second pulsed laser ablation of a material in water invironment with COMSOL package . but I don,t know how should enter pulse of laser  and water . any one can gave me a simple example or some suggestion?
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It may be useful our following article: 
Read full-text
Source Available from: Yoshinari Minami
 
Article: Conceptual study of manned space transportation vehicle using laser thruster in combination with the H-II rocket
Yoshinari Minami · Shigeaki Uchida
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I am producing tin and tin oxide nanoparticles using laser ablation method.I have used de-ionized water, methanol, ethanol and acetone as a liquid media for every liquid varied the energy. The X RD result shows maximum tin peaks while their is no consistency in Oxide peaks.One liquid shows Sn2O3 peaks while in other liquid SnO2 peaks are more dominant along with tin peaks.....Why different oxide peaks are appearing ?
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Check this paper. on laser reacting with water.
"Femtosecond laser ablation of highly oriented pyrolytic graphite: a green route for large-scale production of porous graphene and graphene quantum dots" Nanoscale,2014, 6,2381
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Direct after laser structuring I measure a capacity of 20nF between two areas, this phenomenon disappears after 24h. Has anyone an explanation of this phenomenon ?
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 What is your capacitor, two ITO films with SiO2 as dielectric or two parallel lines with 100 um distance? What is dielectric in last case? Again, what does it means structuring? Your question is clear for the members of your laboratory, but for somebody outside description is not complete. By the way, what is it RAFI?
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I am doing research on nanoparticles using laser ablation method.I am varying different parameters  and  Xrd results show an increase in intensity with increase in laser fluence.
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Definition of laser ablation is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma.  According to this definition, with increasing laser flux it means the temperature will be increase. Sometime when increasing the temperature, the coarsening material will also increase. The coarsening increase, the size particle increases. When temperature increase, the crystallization can also increase. Both of coarsening particle and increase of temperature can contribute to the height of intensity in XRD.
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To study ablation resistance of a polymer nanocomposite material.
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You need to measure or estimate the reflectance of your surface at the laser wavelength.The rest will be absorbed.Conversely, if you know the temperature increase of the surface and the thermal properties of your material (heat conductivity, k, heat capacity,cp, and density,ro) then you can use a simple slab model formulation to deduce the absorbed power, Q(1-R).
T-T0 = 2Q (1-R) sqrt (t) /( sqrt(pi.k.cp.ro), t= laser pulse duration
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Research about quality investigation of laser processed silicon wafer. 
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Another purpose is, to realize an electrical connection fom top to bottom of the substrate. The whole then will be drilled before an metallisation process. 
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I am doing my research on metal nanaparticles by using laser ablation in liquid.. I have observed a decrease in particle size with an increase in laser fluence. 
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1.Pressure of liquid vapor close to its saturated vapor pressure at the melting temperature of the target (hundreds of atmospheres). Reduced droplet sizes.
2. Drops in a confined space may return to the laser beam. Increasing droplet sizes.
3. For a primitive model of the process it can be assumed that the Laplace pressure, stabilizing drop equal to the pressure of saturated liquid vapors.
2. Formula:
2 surface tension of the drop / radius of the drop = vapor pressure.
 Calculate the approximate size of the drop (nanoparticles) to your systems.
Regards.
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I am doing my research on metal nanoparticles by using laser ablation in de-ionized water.The day i prepared my sample i did Uv-vis Characterization to determine the band gap.I placed the sample intact and than did the same characterization after 10 days and observed a decrease in band gap.The color of the sample also changes from grey to milky white.What might be the reason behind decrease in band gap?
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Hi, your metal nanoparticles are very reactives with the environment, while they be smaller will react mainly with the oxygen, it is necesary protect them in inert atmosphere. On the other hand, seriously I find a terrible mistake in your basic concepts. In metals you can`t speak of band gap, because the metals are gapless or their bands are overlaped. The absorption peak seen in UV-Vis is due to surface plasmon resonance.
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Please explain the difference between the spot size and the crater diameter and how to find them? the ablation threshold range of steels machined by femtosecond laser?
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Most popular method being D-square method (https://www.osapublishing.org/ol/abstract.cfm?URI=ol-7-5-196). You plot the square of the crater diameter against laser power/pulse fluence/fluence(if you know w0). This method allows you deduce ablation threshold, w0 and incubation coefficient of any given material.
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while laser beam scan in Pulsed Laser Ablation of material, how can i focus laser beam on a very short area 2cm diameter target, as laser beam scaning area is larger the 2cm.
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There are two methods that can make laser beam scanning on the surface of the target. One is a mechanical device that can move in 2-dimention. You can attach the refractive mirror with this device. Since you are in Beijing, you might be able to purchase from Institute of Physics for this device. Another one is much accuracy but also much expensive/complicated. You can attach the mirror to an electronical-controlled photo-elastic device that can make the focused beam scanning on the surface of the target.
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can we prepare quantum dots  by laser ablation using Nd:Yag laser?
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JOURNAL OF APPLIED PHYSICS 117, 084304 (2015), Carbon 95 (2015) 659-663, J. Mater. Chem., 2009, 19, 7119–7123,J. Phys. Chem. C 2010, 114, 17374–17384,J. Phys. Chem. C 2011, 115, 5038–5043
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How can controlling the space separation between Nps produce by laser ablation in liquid at process .
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Dear Dr. Jassim ,
Did you mean to prevent aggregation or clustering  ?
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I am doing research on tin and tin oxide nanoparticles using laser ablation method. Using Nd:YAG  laser in visible range (532nm) .By increasing the energy i have absorbed an increase in bandgap. What might be the reason.
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Dear  Jafary, nonlinear  grows of temperature with  pulse energy absorbance is main reason of your observation. The  phenomena has  been studied well. I provide You some conclusion from review paper:"Absorptivity as a function of temperature is an important consideration in practice and is usually modelled successfully as a linear function except around the melting point of the metal where there is a significant jump due to the sudden change of conduction electron density".