From my experience - femtosecond (FS) laser pulses ablate any glass and produce a lot of nanoparticles if fluence (surface density of energy) or irradiance (surface density of power) are significantly above ablation threshold. Even if the laser wavelength is beyond any absorption band of your glass, you should have significant ablation and nanoparticle production with 2-mJ pulses. Check your focusing system and reduce laser spot .You did not mention type of the glass matrix for Yb, but for most glasses ablation thresholds are in the range 1.5 - 5 J per square cm. Adjust the spot size to provide fluence about twice the ablation threshold, and you will get a lot of dust that consists of nanoparticles. The bad point is that some nanoparticles get attached to each other and make some kind of net. You can eliminate this effect if vary fluence a bit.

Another hint. After you have made successful ablation in air, consider ablation of the same glass in water. Extensive research results suggest that ablation of solids in water produces much better nanoparticles in terms of size distribution. Just be sure the focused laser pulses do not ionize water in front of the glass slide by proper focusing (may be - to a smaller spot with a lens with higher numerical aperture).

Good luck! Be patient, and you will get the nanoparticles.

Vitaly

Laser ablation is beond my research field of expertise

Vitaly Gruzdev, I forgot to mention you that I actually did liquid phase ablation itself. Actually I do obtain a cloud of particles, and I can even watch them deposited at the bottom of the cuvette. But some how, the peaks of Yb3+ seem to disappear. Does the fluence actually destroy the crystal structure some how ?

OK, now it is clear. First, glasses have no crystalline structure. They are completely amorphous. Action of ultrashort pulses in water can change the structure from amorphous to crystalline. But laser pulses cannot destroy the Yb ions - they must be in the ablated nanoparticles. Absence of the Yb peak may result from low sensitivity of your spectrometer. The layer of the nanoparticle dust is usually so thin that it is not enough to produce any detectable signal for usual/commercial spectrometers for absorption spectroscopy. Probably, you need a spectrometer/spectrophotometer for characterization of thin films and low-absorbing materials. They have improved sensitivity. Try to look around if there is anything like that in your College.

I quite agree with Vitaly. It seems that a luminescence spectroscopy is better to detect RE ions in nanoparticles. May be you can try with Eu3+ or Nd3+ doped glasses for such measurements.As for absorption spectroscopy, the signal is not enogh to be detected in your case (as it was mentioned above).

Yes, Dmitry is quite right - luminescence spectroscopy must work much better in that case. I strongly suggest to use it to detect Yb ions in the nanoparticle deposits. Must work OK.

Vitaly, Dmitry thanks for the suggestions. I tried the 2F5/2→2F7/2 emission in Yb3+ at 980 nm excitation from the ablated samples. I didn't get much luminescence signal from it. This might be possibly because of the fact that the sample was treated as a suspension in water, as resulted from LP-PLA. Water has heavy absorption in the NIR and it might be killing all the luminescence by re absorption. Can you suggest any other solvents for LP-PLA having less absorption in NIR ? I know most of the organic solvents are not that safe for ablation !

Alternative solvents are alcohols, but I am not sure they can survive high laser irradiance close to ablation threshold of glasses. I have not done ablation experiments in alcohols. There is also one important point. If you produce dielectric nanoparticles in polar liquids (like water), the nanoparticles tend to agglomerate (stick to each other) and deposit to walls of a cuvette pretty fast (about 1 minute) due to electrostatic interactions. Stable suspensions of dielectric nanoparticles in water are usually obtained by covering them with either polymers or organic/biological molecules. That is not your case. So, it may happen that the ablated nanoparticles get deposited at walls and bottom of your cuvette before you start doing luminescence spectroscopy. I would suggest to dry out the liquid after the ablation experiments, break the dried cuvette into pieces and do luminescence spectroscopy at the bottom part and the lower parts of the walls where you would expect deposition of the nanoparticles. Again, in that case you have to deal with thin deposited film of the nanoparticles (that is not homogeneous and consists of islands). That means, you will need very high sensitivity of your spectrometer/photospectrometer.

Vitaly Gruzdev Indeed, that makes sense. I had actually tried to take the particles our by centrifuging, and then drying them to change the solvent. But again I used ethanol, another polar protic solvent. Probably that again caused the particle to settle in a minute.

Here is my letter about the synthesis of Yb by laser ablation: P. Calandra et al. Materials Letters 64 (2010) 576–579

common solvent are not useful. the causes have been discussed, traces of surfactant is a winning approaches. This also can be seen as a winning synergy between top-down and bottom-up approach.

Thanks Pietro !! That was helpful, I would not have found your publication otherwise !