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Femtosecond Lasers - Science topic
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Questions related to Femtosecond Lasers
Hi, I'm wondering how I can calculate the fluence of a laser from given parameters . like we have femtosecond laser with Bessel Beam .
1-160Mirowatt Power on power meter
2-10 Hz frequency
3-Beam spot diameter is unknown
4-50x with 0.6NA optical lens
According to the equation Fluence will calculate by F=E/A. But i am confused about Total power ,power on power meter ,pulse energy , laser spot diameter and the A in given equation. Is there any way to calculate the (fluence) of this laser from the mentioned parameters? what's the mathematical relation between given parameters
I would be truly grateful if anyone could answer me.
Exploring the Feasibility of Anode-Free Lithium-Ion Batteries with Femtosecond Laser Microfabrication
I'm delving into the potential of femtosecond laser microfabrication for creating anode-free lithium-ion batteries—a concept that could revolutionize energy storage. Anode-free designs aim to simplify battery architecture, enhance energy density, and potentially lower costs.
However, such systems face critical challenges, including:
- Ensuring stable lithium plating/stripping during cycling.
- Mitigating dendrite formation and electrolyte decomposition.
- Achieving precise microfabrication to optimize electrode structure and surface properties.
Femtosecond lasers, with their high precision and minimal thermal effects, seem promising for tailoring electrode surfaces to enhance lithium deposition and cycling stability. But how far can we push this technology?
🔍 Questions for the community:
- How can femtosecond laser processing be optimized for scalability in battery manufacturing?
- What are the most promising materials for such anode-free designs, and how does surface engineering impact their performance?
- Are there existing studies that successfully integrate femtosecond laser microfabrication with practical battery applications?
I’m looking forward to hearing your thoughts, insights, or references to related work. Let’s brainstorm ways to overcome these challenges and advance the next generation of battery technologies!
It is hard to find such parameters. I know it can work at least 2 weeks continuously. Has anyone tried longer? really curious about the limit.
I want to know what is the reason that at the end of Bk7 crystal there is something like a bend, I have attached a picture to be clear.


I am doing a comparative study of different pulse stretching and compressing techniques which are used in the Chirped Pulse Amplification Systems. On what all basis can we do a comaparison of different techniques? Which is the best method to the comparative study?
Hi ,
I want to monitor supercontinuum on OSA and for that purpose first I couple supercontinuum into SMF (PM-980) and other end to OSA. I am wondering since the loss is wavelength dependent and at shorter wavelengths we have high attenuation constant (~6dB/km), I could see red light in the generated supercontinuum but OSA does not show any IR wavelength and SC starts from 800nm to 1600nm. Is it because of high attenuation on those wavelengths or something else is going on. What type of fiber one should use in such situation.
Thanks
Hi we want to see the laser pulses(femtosecond pharos, 1030nm, 100KHz, 180 fs) with oscilloscope, what should be the settings we need to play with to see the signal from the photo diode detecting the laser pulses. we try to change the vertical and horizontal divisions(50 mV and 2 ns) this is what we got we got.

or we can use light with lower frequencies in the range of MHz?
Hi there,
I hope you are doing well.
Do you know, which camera is used recently for the GRENOUILLE technique in order to measure the pulse length of ultra-short pulses?
what features the camera should provide? Should it be fast or regular camera works as well?
This article names a camera but I am not sure it is used recently in experiments or it is out of date!
Attached is a document in this regard.
I appreciate your time and any feedback.
Best regards,
Aydin
I have shadowgraphs of plasma filament formed in air by focusing a femtosecond laser and I am trying to solve for refractive index change in the region using the shadowgraph. The contrast value at each pixel is a source term for 2D-Poisson equation.
I can apply the Dirichlet boundary condition at the top and bottom of the image. But the left and right corners contain sections modulated by the filament.
What type of boundary conditions should I use in this case?
Is there any nonlinear process through which a 0.8 micron femtosecond laser pulse can be used to efficiently produce radiations in the range of 1 - 1.5 microns.
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.
Usually the terahertz source used for terahertz communication is a continuous terahertz wave generated by differential frequency, then can terahertz pulses generated by femtosecond laser be used for terahertz communication?
I want to generate second harmonic of 1600nm component from the octave-spanning supercontinuum to beat it with 800nm component and detect CEO signal. What are important specs on deciding an optimal SHG crystal.
Also, What should be the crystal acceptance bandwidth or how to estimate it.
Thanks
I wanna calculate spatial profile of laser-induced heating with a temporal evolution.
System is like a 100-nm thick film of gold (Au) deposited on a 7.4-um thick yttrium iron garnet (YIG) on a gallium gadolinium garnet (GGG) substrate. This system is heating up by absorbing of 100-fs laser pulse, e.g. 525-nm wavelength.
Looks like it is possible to use Comsol Multiphysics or Lumerical for this task but I haven't found any real solutions or applications of performing this calculation in such softwares.
Hello everyone,
Normally, I use the autocollimation technique in the case of a cw laser which implies the use of an additional objective lens (OL) right away the laser to wider the beam. However, in the case of a pulsed fs laser, I would be concerned about the group delay dispersion (GDD) of the OL. Obviously one would suggest to use a GDD-minimized OL for this aim but maybe there is another way to collimate the beam without having to buy an additional OL. Beam divergence of the laser is < 1 mrad.
Would be thankful for sharing your expertise (if any).
Who have the phd thesis on the spectrum of terahertz radiation from fs laser induced air plasma? If you have one, can you tell me the title of the thesis? Thank you for your kindly help!
I understand at high pulse energies you can machine visible patterns on quartz. How do we tune the energy/other parameters to form patterns which are only visible after etching with HF or KOH?
how to do f-2f interferometry from an octave spanning supercontinnum with frequency spacing 120MHz. Which would be the most suitable optical filter in this range for filtering f and 2f components from supercontinnum, to detect carrier envelope offset frequency of a mode-locked laser.
Thanks in advance!
The principles of wavefront reconstruction based on a geometric-optical reflection of reconstructing light from the surfaces with constant phase differences between the object and reference waves can also be used for a temporal reconstruction of the object ultrashort pulse [1]. This can be illustrated by the following simple example. Let the object beam consists of two δ-pulses delayed with respect to each other by τ. We suppose that the object and reference beams propagate in opposite directions forward to each other and also that δ-pulse is used as the reference one. In that case the interference fringe structure will consists of two parallel planes separated by a distance τc/2 where c is the velocity of light. If we use the δ-pulse for reconstruction it will be reflected sequentially from one plane and then from the other. The time delay between two reflected pulses will be equal to τ. So, the object pulse temporal structure was reconstructed by simple geometric-optical reflection. The question is: How this mechanism of the object pulse temporal reconstruction relates to the known methods of time-resolved holography ([2, 3] and other)? 1.https://www.researchgate.net/publication/238033164_Ultrashort_light_pulse_scattering_by_3D_interference_fringe_structure
2. Rebane, A., & Feinberg, J. (1991). Time-resolved holography. Nature, 351(6325), 378-380.
3. Mazurenko, Y. T. (1990). Holography of wave packets. Applied Physics B, 50(2), 101-114.
Working on a femtosecond laser which is mode locked, we can not change the pulse energy and wavelength so we have to change its fluence
hi,we want to build an Ultrafast Transient Absorption Spectrometer system, how to choose a spectrometer?
We already have femtosecond lasers system (coherent) ,pump probe system(home built), white light white-light supercontinuum(use CaF2 or Al2O3),
We don't know how to choose a suitable spectrometer, what products can be recommended?
We would appreciate it if you could help.
There is a femtosecond pump beam with a central wavelength of 800 nm, pulse duration of 150fs and repetition rate of 1kHz used to pump the OPO/OPA system with Ti: Sapphire (to get white light) and BBO crystals to get tunable infrared radiation in the spectral range of 1200-1600nm. Interested to know how much the initial 150fs pulse duration could change and how to calculate it. There is no current option to measure it, unfortunately. Thank you.
Consider the scenario,
input pulse width and spectrum = 700fs/ 2.23nm (after propagating thru 20cm SMF)
Output pulse width and spectrum become = 1.183 ps/ 38.357nm
How to select a compressor (Grating pair or the one more suitable) to compress output pulse with of 1.183ps to its fourier limit.
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 trying to couple light from Laser with M^2=1, wavelength = 1030nm and beam diameter = 1.3mm. Please suggest a lens for efficient coupling into PCF (say 2um core). As far as I know, I have two options, either to use Aspheric lens or Microscope objective, however, I am not really sure which one would be a best choice. As I understood (Please advice if right or wrong)
For efficient coupling, these points should be considered.
1) N.A of lens should be equal or close to that of fibre (PCF)
2) Lens focus diameter should be equal to core size of the fibre (PCF)
3) Input beam should be parallel to Optical axis (Collimated)
Please advice.
Thanks
Dear professors and colleagues,
I am going to to study effect of the two photons absorption in Safranin O. Safranin O is organic material, so I think that the power needed to activate this effect doesn't need to be too high. However, the two photons absorption is a third-order nonlinear optical effect, so it is usually implemented with high-power pulsed lasers. I cannot afford to buy high-power pulsed lasers. So, can I stimulate effect of two photons absorption in safranin O by continuous wave laser (808 nm or 1064 nm)? And how much is the required power of laser? I hope the colleagues who have experience in this experiment share me useful information.
I look forward to hearing from you. Thanks in advance.
Yours sincerely.

Do there exist any compounds, fluorophores, dyes, quantum dots, phosphors etc that can emit or fluoresce non-linearly without needing ultra-high intensity illumination (such as pulsed femtosecond laser)? That is, with a UV led for example and with this non-linear emission being dominant?
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?
I am using a femtosecond laser (Ti-sapphire) which has pulse width 200 fs. Now, I want to change the pulse width from 200 fs to ps range using glass rods for our microscopy application. But I do not have any idea how to check the pulse width?
As part of a project proposal that I am working on as an intern at the Canadian Light Source, we are looking at the effects on the production and transport of an electron bunch produced by photoemission of chirping a pulse from a femtosecond laser from approximately 35 fs to approximately 10 ps.
In order to design an appropriate system to produce this chirp and understand what the chirped pulse profile will look like so that I can model the resulting electron bunch, I have been trying to find some open source software that would allow me to model the pulse chirper and its effect on the pulse profile without success. Does anyone know of a program that would be suited to this task?
The femtosecond laser ionized air can form a filament of a length of centimeter, and broadband THz wave can be radiated from the filament. The plasma density at both ends of the filament is different, and the phase of the radiated terahertz will be different.
So, which factor can change the phase of the THz waveform? What is the physical mechanism behind the change of the phase of the THz waveform?
Hello
I am searching to find a code for describing and simulating interaction electron beam with femtosecond laser in vacuum.
notice : I don't have ions or plasma in my simulation. I have just electrons.
I am trying to build a pump-probe system and I need to find the "time zero" between a pump pulse (@800 nm, ~50fs generated by Ti:Sapphire fs amplifier) and a probe pulse (@530 nm, ~50 fs, generated by an OPA). The delay line I built can create a maximum time travel difference of ~4ns. I have measured approximately the length of the optical path of the two beams (I set the delay line in approximately the middle point of the travel line) and set up the system so that the two beams meet after approximately the same travel distance. My plan is the following: I will set the OPA @ 800nm and I will put a 50:50 beam splitter in the meeting point of the two beams and finally collimate after that the two beams. Then I will monitor with a fiber spectrometer their spectrum and by scanning the delay I am expecting to see the spectral interference of the two pulses. Finally I will set the OPA at the desired wavelength and replace the beamsplitter with a dielectric mirror and realign and begin the experiment. I hope it will work but I am wondering if there is an easier and more efficient way?
"Beyond this point, with shorter focal length lenses, the diameter of the self-focal zone can no longer increase because the geometrical focal diameter becomes smaller. That is to say, external focusing becomes dominant and there is practically no distinction between geometrical focusing and self-focusing. Therefore, the diameter of the laser beam is limited by the strong external focusing of the lens, as observed in insets of Fig. 3 where the plasma column diameter decreases for shorter focal length lens."
what is the difference between external focusing , geometrical focusing and self-focusing. I am confused with this three concepts. Who can tell me the difference between this three physics concpts?
We are a research group working in the field of laser processing. We want to build our own femtosecond (or picosecond laser) for micromachining (fine marking for example). Do your know any low cost solution ? (publications, reports, do-it-yourself instructions, simple low cost source, etc...). Thanks for your advice and contact me if you having complete discussion : mflury@unistra.fr
A two-color femtosecond laser is transmitted in the air and a positive group velocity dispersion occurs. Negative group velocity dispersion is introduced when a-BBO crystal is added to the optical path. Can someone explain to me what is a positive group velocity dispersion and negative group velocity dispersion in simple sentences?
The femtosecond laser can form a plasma in the air, and broadband terahertz radiation is formed in the plasma due to the oscillation of positive and negative charges. We know that there are two main frequencies involved. One is the oscillation frequency of the plasma and the other is the peak frequency of the terahertz spectrum. The usual study considers the peak frequency of terahertz to be the intrinsic oscillation frequency of the plasma. Is the oscillation frequency of the plasma and the peak frequency of the terahertz really equal? What are the main factors determining the peak frequency of the terahertz spectrum?
The femtosecond laser ionizes the air to form a plasma from which terahertz waves can be radiated. The current mainstream models describing the mechanisms generated by terahertz waves are ionized photocurrent models and four-wave mixing models. I have always had a confusion: we know that terahertz waves belong to electromagnetic waves, and electromagnetic wave radiation can be explained by the energy level transition theory. Why cannot one use the energy level transition theory to explain the generation mechanism of terahertz waves? Or does the theory of energy level transitions not apply to the generation of terahertz waves at all?
I need information for reflective(not refracting) type microscope objective for working with femtosecond laser pulse system.I find maximum maximum 40x reflective objective, but i needed more magnification. Can any body suggest me higher magnification reflective type objective which is dispersion free in visible range.
Which is suitable microscope objective with mangification 100x or less for time dependent studies and Imaging in Femtosecond laser system?
I am conducting research to investigate the safeguards technology applications of cavity ring down spectroscopy with a femtosecond laser. I am inquiring to see if any past CRDS experiments have been conducted with femtosecond lasers.
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,

Hi there,
I hope everything goes well.
I want to be familiar with molecular dynamics and Coulomb Explosion Imaging (CEI).
Could you please explain what COLTRIMS, VMI and TOFMS do? and in which applications they are used? what are differences?
Do we choose them related to our applications? Do they depend on light sources (X-Ray, Femtosecond laser pulses, Ion impact / electron impact collision) or other things?
What are advantages and disadvantages of them?
and at the end, are there such other apparatuses like them to image the molecules?
Bests,
Hi there,
I hope every thing goes well.
Today I face with a question that I want share with you.
What is the exact difference between Electron impact ionization , Highly charged ion ionization, X-ray ionization and femtosecond pulsed laser ionization?
and which method do this ionization process? for instance, Two/ multi photon absorption, distortion of potential well, tunneling, single photon absorption and so on.
Please let me know.
Bests,
In a chirped pulse amplifier (CPA) one uses a short femtosecond laser pulse and then amplifies that to the pulse energy scales of terawatts and pentawatts. In doing so a stretcher and a compressor has to be used along with the pulse amplifier. Initial pulse is stretched then amplified and then compressed again. Such ultra short laser pulses have broad spectral bandwidth, a property which is used in it's controlled stretching/re-compression.
Would appreciate for sharing the trustworthy references for measured nonlinear refractive index for fused silica (quartz) for femtosecond laser pulses preferably in the region of 800nm wavelenght with around 120fs pulse duration. After checking the literature been found that the quartz value for n2 differs for several times (excluding quite strange values) but somehow is of the order of 10(-16) cm2/W. Thank you.
corneal rings considered one of the new surgical procedures for the treatment of keratoconus, femtosecond laser allow precise location of the tunnel deep in stroma and also precise heigt that prevent dislocation of the rings during surgery
This is feasible - sse the following publication:
A. Schiffrin et al, "Optical-field-induced current in dielectrics", Nature, v. 493, p. 70 (2013).
I am looking for a collaborator to do experiments. I have a femtosecond laser to excite the photocurrents. I have no expertise in ultra high-speed electronics and detection of the current.
in the current context, the automotive industries are forced to reduce carbon dioxide emissions as part of the European H2020 program.
To do this the reduction of friction is a primary lever. In fact, automotive manufacturers are trying to find solutions such as downsized engines for example to lighten the weight of vehicles but they compensate for their relief by a higher need for power
The non-holographic mechanism of achromatic wavefront reconstruction is based on a geometric-optical reflection of reconstructing radiation from surfaces with constant phase differences between the object and reference waves used to record the interference fringe structure in the medium bulk [1]. This mechanism was realized by femtosecond recording of the interference fringe structure in very thick medium [2]. However, it seems that some experimentally easier ways of realization are possible. Maybe some other waves instead of light can be used, etc. Can anybody suggest a new method of realization of the non-holographic mechanism of achromatic wavefront reconstruction?
PLD technique relies on laser with high peak power to ablate various targets. Mostly nanosecond pulsed lasers (UV) are integrated commercially. Why not they use picosecond or femtosecond laser which could deliver high peak power and less thermal effect?
I may obtain a titanium:sapphire oscillator. I need to build an amplifier that is cheap. I have no prior experience in femtosecond physics, though I deal with optics and in the past dealt with nanosecond sources.
We would like a 2P optogenetics rig for as cheap as possible. Ti:Sapph are nice tunable lasers but not really cheap. Ideally we would want a femtosecond pulsed laser about 920nm, but lasers are a lot cheaper around 1040nm.
It looks like that the excitability of ChR2 is low but not zero at 1040nm. I am not sure if this means 1040nm is suitable for ChR2, or maybe it would require power levels that exceed safe levels for the animal. Has anyone tried this?
I know we could use 1040nm with a red-shifted opsin, but we would prefer not to.
I'm studying brass drilling with a femtosecond laser. The holes I get are narrow (10-20 microns) and with a depth greater than 50 microns. The confocal microscope I have available is not able to detect the bottom of the hole. Any Suggestions?
I am using DPSS continuous wave laser to study Nonlinear optical properties say it Z-scan technique. What else I can research using these sources, I just want to try something new with the available facility. Any answers would be appreciable. Thank you for your ideas in advance..
I used femtosecond laser to do ablation in producing silver nanoparticle. In order to create the good coloid, i have to make the beam focused, how can i get the new focused beam in medium? How to calculate the new focused beam size, so that the focused beam touch the silver plate
I have prepared nanoparticles using laser ablation method. I have used 2nd harmonic beam, and prepared four different samples in de-ionized water by changing laser energy (60, 120, 180 and 240 mJ) . I kept the time constant i.e 40 min.
I have observed that the PL and Raman peaks increases when the laser energy was 120mJ then peaks intensity decreases at 180mJ laser energy and then again increases at 240 mJ. What is the reason behind it?
I have read that the intensity increases due to the increase in particle size
However in my case the particle size increases with the increase of laser energy.
The peaks intensities are increasing randomly
I know it must be less than 1 ps, but anyone have a more precise knowledge about it?
Soliton Formation and Superluminality Effect due to Nonlinear Absorption of Femtosecond Laser Pulse Energy.

I want to build a noncolinear geometry pump probe femtosecond setup.I want to know how to determine the time zero ?in a colinear geometry,this is easy. thank you for your help

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
What are the ways to applying chirp effect on the frequency of electric field in a femtosecond laser pulse?
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.
I know as least for nanosecond, or even picosecond, laser in which there is enough time dumping out energy that will be absorbed by Si. However, as for femtosecond laser, the times seems to be too short for Si to absorb making electrons jumping into higher energy band level. I have seen some papers in which femtosecond laser is used to treat Si material surface. I fail to understand why it works and what is the detailed explanation towards scenario.
Thanks in advance
Chenjin
what is mean by broad band and why the short laser pulse (ps or fs laser) means broad band laser ?
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?
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
I study the picosecond self-mode-locked laser recently, i want to know how can i determine the dispersion regime of mode-locked operation with spectral shape and the time‐bandwidth product?
Currently we are using a standard telekom phase modulator for the repetition rate control of a femtosecond laser. When upscaling the intracavity power the laser doesnt operate properly. Are there commercial compact fiber coupled MgO doped LN phase modulators at 1550 nm available ? The Lithium Niobate could show whether a waveguide or bulk design. Nevertheless the bulk PPLN should be confined within a micro-optic package hence it needs to be very compact. Cheers, Sebastian
I have a femtosecond laser (800nm, 1 kHz, 50 fs, 4 mJ) and want to focus with off axis parabolic mirror to a spot size of less than 10 micron. I can focus but difficult to get good quality of focus. generally I obtain bright tiny yellow (if seen on pink paper) spot at the center after focusing however the periphery has also either the hot spots or some distribution of high intensity component. I mean the beam is not fully concentrated at the center. What is remedy you can suggest to me to achieve my goal. what is the proper shape of focused spot? Thanks in advance and appreciation for any kind of suggestions and comments.
What is the cause/origin of non linearity or non linear behavior in materials like dyes,2-d materials etc and what are the unique properties that material should possess in order to show non linear behavior,when it is irradiated by a Laser beam?
Suppose there are two Raman peaks and both of them show a shift with pressure. But one of them after certain pressure start to come back to original Raman peak position i.e. without pressure position. What does this mean? Please comment on this
Suppose there are two Raman peaks and both of them show a shift with pressure. one of them after certain pressure start to come back to its original Raman peak position i.e. without pressure position. Please comment on this.
There are two major techniques to measure ps - fs pulses of the mode-locked lasers:
I) Steak camera
II) Optical autocorrelation
According to the space-time transformation in second-order autocorrelator, what is the function of the nonlinear crystal ( KDP or BBO) leading to the interferometric autocorrelation to display the amplitude-coherence behavior of laser sources?