Science topic
Ultrafast Lasers - Science topic
Explore the latest questions and answers in Ultrafast Lasers, and find Ultrafast Lasers experts.
Questions related to Ultrafast Lasers
Can ultrafast lasers be used for carbon fiber ablation.
I use a mechanical translation stage with a retroreflecting mirror as a delay line (fs laser - gate(pump)). Despite the retroreflecting mirror ensures getting parallel beams (in & out beams), I noticed a laser beam drift when I scan the translation stage over relatively long distance, i.e. approximately 100 mm back or forth from the mid-point.
I know this can cause troubles for my experiments, particularly I use collinear geometry for pump(gate)-probe experiment, hence both beams must coincide without deviation upon scanning the delay line.
Can any one please tell me, how can I correct that ?
The nanosheets which I've synthesized are photocatalytically active. I found that these nanosheets when irradiated can reduce metal salts, thereby forming a nanocomposite. I'm trying to unravel the exact mechanism behind this activity. I know that transient absorption spectroscopy and ultrafast laser spectroscopy are few techniques that can be employed to understand the charge carriers that are being generated in the material. My question is, are there more techniques which can help me get more information about my nanomaterial?
I am looking to find possible methods to temporally overlapping a nanosecond pulsed laser (280 Hz - ~ 6 ns - 532 nm - beam diameter ~ 4 mm) with a picosecond pulsed laser (78 Mhz - ~ 10 ps - 565 nm - beam diameter ~ 4 mm) with delay line mirrors.
ATM I am using a fast PD with 1ns Rise Time (https://www.thorlabs.com/thorproduct.cfm?partnumber=DET210/M) and a 10 GS/s oscilloscope. However, I only can see the attached signals coming up from ns and ps sources when they run separately, and since the amplitude of the detected signal from ps is much low (~20 mV), it is hard to adjust the other one with it. One way which comes to mind is to lower the intensity of the ns laser with density filters but is there any other alternative to this.
Let me know if more information is required.


With ultrafast laser we normally get a smooth and white sidewall and edges of laser cutting, but for some thick ceramics substrates we have to cut with fiber or CO2 lasers, and there is burs and black oxides around the edges and sidewall how to clean it completely?
We have tried some acid and sodium carbonate, but still yellow marks left
Thanks
I am aware of many femtosecond laser based approaches to excite phonon modes e.g. in crystals and minerals. Quantum Cascade Lasers (QCLs) seem like an interesting alternative, especially since they can be tuned by frequency and can be operated continuously. Has someone tried to use QCLs to excite phonon modes? Or is there a catch?
I am doing a SHG experiment on the 0.3-mm-long BBO crystal with an 50fs ultrashort pulse (130uJ, centered at 1030nm).
At the beginning we start from 27GW/cm2 peak intensity, and the SHG efficiency is not too far from the calculation (~12%). Then I reduce the focused spot size to increase the intensity up to 1.6TW/cm2, but the SHG efficiency only increase to ~35%.
I would like to ask about the damage threshold of the BBO crystal under this kind of pulse duration, and what are the possible reasons that why the SHG efficiency is limited.
Hi there,
I hope every thing goes well.
As we know there are some techniques in generating ultra short pulses such as active mode lock (Acousto-optic / Electro-optic modulator) and passive mode lock (saturable absorbtion or kerr lens effect) and also hybrid mode lock (which contain both active and passive methodes).
And we know that kerr lens effect is a phenomena that works in ti:sapphire lasers.
Question here is why by focusing the pulse in the medium, it causes mode locking and what is the the exact role of adjustable slit in the cavity ?
Please explain more detail about this.
Bests,

I am trying to calculate increase in lattice temperature of a permalloy film after approach of ultrafast laser pulse resulting ultrafast demagnetization and remagnetization. I have the parameters of the laser pulse and basic characteristic parameters for a permalloy film with me. How one can estimate the lattice temperature in local thermal equilibrium from a simple equation without knowing the phonon modes or without involving any coupling constants with rigorous modeling? Is it possible using some form of Debye model?
Take a1% Nd:YAG rod of 6cm length & 6mm Diameter and by side pumping exposed length by Laser diode is 4cm . Does the unexposed area also participate in gain, extraction energy etc . How does it involve in lasing?
What is the bandwidth (in eV) of a transform limited pulse with a (100 as) pulse duration?
While using laser to irradiate surface of a conductor like copper for ex. ((Is the pressure or density of ablation environment effecting the free electron behaviour in the surface ?? ))
For example it changes the spinning direction or effecting the coupling mechanism between incoming photons with free electrons in the surface ??
Hello everyone,
I did some research of how to measure with IVIS and which opportunities I have... I found lots of advantages for the unit photons per second but u can also use counts per second as a unit. so I was wondering when should I use counts and when photons per second? can anyone help?
To date, the methods to measure the topological charge of optical vortex beams are based on continuous wave. When the OAM beams are pulsed in femtosecond domain, how to measure the topological charge of ultrafast optical vortex beams ?
Typically, ultrafast pulse laser is realized by mode-lock technology and commercial products are available now, however, for most products, they only give pulse-width data, and the spectra-width data is “neglected”, of course, in most industrial application, that's not important, but for some quantum study, that matters. For example, some picosecond (<15ps,1064nm) laser's spectra-width maybe several times larger than its Fourier-Transform-Limited value, ultrafast pulsed fiber laser maybe even more worse. What's the reason behind? And could someone give me suggestions how to get the ideal pulse? Thank you!
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
The relative intensity noise of the laser diode should be lower than -155dBc/Hz @10kHz , and the output power should higher than 16dBm.
Factors affecting the performance of optical frequency comb.
what is mean by broad band and why the short laser pulse (ps or fs laser) means broad band laser ?
After reading through Swamp Optics' website (http://www.swampoptics.com) I got convinced that the best way to measure and characterize ultrashort laser pulses (ps/fs long) is using their products, and specifically GRENOUILLE.
I'll be happy to hear more on this subject, preferably from someone who has worked in this field or even with this device and can share some insights about its pros and cons.
Thanks,
Assaf
Looking back on about 30y of femtosecond optics and spectroscopy, I would like to start a discussion on which achievements active researchers today consider as, e.g. most valuable, as a break-through, most visionary etc. To be specific, I'm not looking for top-ranked papers but a more general idea/concept/invention/technique/method that has in your opinion revolutionalized the field, has paved the way for succeeding studies and/or has been picked up by other branches / has inspired researchers in other fields such as biology, chemistry or even industry.
I think 6fs will spread to be about 30 fs if pass through 1 mm and about 56 fs if pass through the 2 mm of Bk7.
For 18 fs , it will be 22 fs if pass through 1 mm and about 24 fs if pass through the 2 mm of Bk7.
For 30 fs , it will be 31 fs if pass through 1 mm and about 32fs if pass through the 2 mm of Bk7.
What is your opinion and if you have some related papers please?
I was reading some papers about mechanism of ultrafast laser ablation on metal specimen.
'Metal direct vapor' or ' plasma ' show up several times [1].
Does that mean that metallic bond has been destroyed due to energy input?
How could it happen?
According to solid state physics, metallic bond formed by 'electron cloud and positive ion' holds metal together.
During laser ablation, photon transfer energy to electron. Energy received will turn into kinetic energy to accelerate electron. Electron will hit other electron or lattice to transfer energy [2].
[1] Momma, Carsten, Boris N. Chichkov, Stefan Nolte, Ferdinand von Alvensleben, Andreas Tünnermann, Herbert Welling and Bernd Wellegehausen. "Short-Pulse Laser Ablation of Solid Targets." Optics Communications 129, no. 1–2 (1996): 134-142.
Because we can see in some publications that HRS is incoherent. But both of process are spontaneous and coherent NLO processes. How can you differentiate in your experiments?
Hi, has anyone worked with a nano-second pulsed LASER with OPO unit ? What is the spectral width of the beam after the OPO/OPA unit ? What are the possible ways to measure the spectral width of the beam (maximum resolution of normal visible/IR detector is 6 nm).
Specifications : Pump wavelength - 1064 nm, Rep rate - 10 Hz
The laser pulses will be given entire histogram(i. e. the total time scale) or will it be given at the initial time, on the X-Axis at time x nanosecond the fluorescence is about 80% compare to the initial counts intensity, here it is not clear that the 80% counts and then single photon counting ?
what are their (femto, pico second pulses ) advantages over nano pulses.
Hello.
We have Ti:sapphire ultrafast laser. In oscillator, the bandwidth of the Kerr-lensed mode-locked (phase-locked) laser is exceeding 60 or 70 nm. After passing through two amplification stages the bandwidth is significantly reduced to about half or even lower. As we need shorter pulse duration as much as possible, It is very great to implement some technique to reduce the spectral narrowing during amplification. One method I've heard is that there is special filter making spectrum flat before entering amplification. Could you give me some idea?
As we know LIBS is mainly used for the elemental analysis of a material. Is it possible to use femto-second and atto-second lasers? If it is possible then which is a suitable technique and why? Is there any papers related to the elemental analysis by femto-second and atto-second lasers technique? Please give the reference also. Thanks.
Hi,
Does anyone have or know where to get a cytokinin reporter system using a TCS promoter driving GFP or GUS expression?
It will be really appreciated if you would like to share such constructs.
Chen.
Hello,
I am doing some time resolved emission measurements on CdSe quantum dots using TCSPC. Generally, my samples show multi-exponential decay having 3 or more lifetime compoents. Out of these, one component has a very large lifetime (50ns or higher) which I am not able to resolve using the fast TCSPC setup. The lowest rep rate I have is 20MHz (TAC window = 50ns) and therefore my sample doesn't decay completely in the given TAC range and get re-excited again. Therefore, I am only able to collect a small portion of the whole decay profile. I tried to resolve the longer lifetime component using tailfitting (as lifetime>>>FWHM of IRF ~ 200ps) but since I don't know the decay background, I am not able to get a good value for this component (as the longer lifetime is very background sensitive).
I thought about using a blank (solvent) and collect time resolved emission for the same amount of collection time under similar experimental condition to get the decay background and use this value during the fitting. Is that a good way to figure out the decay background?
What else can I do to measure the complete decay profile or calculate all the lifetime components using this setup?
I am also considering sending back the laser to the manufacturer and changing one of the rep rates 80MHz to 1MHz to increase the TAC window to 1micro-second and thus be able to collect the full deacy.
Thanks,
Saurabh
The use of gas-filled capillaries and dispersive elements is very popular to compress transform limited pulses, for example at 800nm, for femtosecond millijoule pulse (i.e. starting from 100fs scale).
There are examples of investigations of compression in solid bulk media. I would be very interested in someone sharing his thoughts or even his experimental experience on the problem.
Specifically, how to manage the significant transverse modulation when focusing nonlinearities ariseing in bulk solids. What type of materials could be suitable at 800nm and maybe what are the limits in which this approach does/does not make sense (in light of building a very compact nonlinear compressor for free-space pulses)?
%Please vote the questions and answers you like%
I was reading an article about high harmonic generation in Ar gas and didn't understand the term Cooper minima and its significance.
For planning photonics exhibition visit: I'm asking for 1st-level directioning regarding what lab equipment one should see while starting to design an ultrafast/non-linear pulse compression lab.
There are a number of commercially available replacement for standard Ti:Sa 800nm femtosecond oscillators, mostly duplicated 1560nm laser that produced sub-100fs pulses at 780nm.
Could you report your experience about this?
How do they compare with standard Ti:Sa solutions in terms of price, performance and reliability?
Do you have experience with specific brands and designs?
Some companies even propose them to drive regenerative amplifiers.
Thanks
Marco
I am working on the Kerr rotation measurement from MOKE using ultrafast laser [785nm, 80MHz repetition rate]. When applying 2mm-thick PDMS onto a magnetic film, we did not see the change of measured Kerr rotation angle from both the static MOKE measurement or time-resolved MOKE measurement compared to measured without PDMS (in air). However, when checking with the theoretical calculations, there is a clear dependence on the index of refraction of PDMS [You C-Y, Shin S-C (1998) Generalized analytic formulae for magneto-optical Kerr effects. Journal of Applied Physics 84: 541-546 doi:http://dx.doi.org/10.1063/1.368058]. Does anyone know whether the Kerr rotation changes with the adjacent bulk medium under this situation?
Does anyone know a formula to calculate the heating and cooling rates in a femtosecond laser? How can we measure the temperature during laser processing ?
The focused spot is very asymmetric after the pulse is reflected from two gratings, in which one grating contains the burn mark for a pulse compressor. Although we tried to align and make the beam in parallel between two gratings, we could not focus the beam (calculated FWHM is 40 um but measured beam is 50 um x 200 um). Do you know if the burn mark on the grating can cause the asymmetric focusing? Or does it just come from the misalignment of two gratings?
The decay rate of a fluorescent or phosphorescent material is linked to the radiative decay rate and the photoluminescent quantum yield (PLQY) which can each be measured absolutely using both a Time-Correlated Single Photon Counting setup (TCSPC, for radiative lifetime and hence radiative decay rate) and an integration sphere (for the PLQY). The issue is that the non-radiative decay rate is an umbrella term for different non-radiative decay modes, such as concentration quenching at high chromophore densities. How can the intrinsic rate be separated from these other decay modes?
Nonlinear Optics in Vacuum
What is the exact mechanism ruling the predicted nonlinear optical process in vacuum at super high peak field? What exactly are the experimental proofs?