We had put around 1mM of Rh 6G in a parallelepiped glass cuvette and pumped it using an Nd:YAG laser. We obtained a bright collimated beam (with the peak centred inside the PL of the dye) and the peak was sharp with an FWHM of ~3nm, other than the enhanced PL of the dye. When we replaced the cuvette with a glass vial we got only the enhanced PL. Is because the TIR inside the cuvette somehow assist in lasing of Rh 6G? Or is it random lasing ? The pump energy was ~2mJ.
At this level of the pump can be readily lasing a solution of rhodamine 6G in ethyl alcohol in a plane-parallel cell 1 mm thick when pumped by the second harmonic Nd: YAG laser operating in a pulsed mode. When replacing the cell in the solution of the same dye in a glass vial lasing will not, because in this case there is no feedback provided by the cell walls. Random lasing in these conditions is only possible by dissolving the rhodamine 6G in a strongly scattering medium.
At this level of the pump can be readily lasing a solution of rhodamine 6G in ethyl alcohol in a plane-parallel cell 1 mm thick when pumped by the second harmonic Nd: YAG laser operating in a pulsed mode. When replacing the cell in the solution of the same dye in a glass vial lasing will not, because in this case there is no feedback provided by the cell walls. Random lasing in these conditions is only possible by dissolving the rhodamine 6G in a strongly scattering medium.
In principle, you should be able to avoid or decrease residual Fabry Perot reflections from the cuvette walls, by tilting the cuvette with respect to the pump beam,
If you see a single peak with 3 nm width, I understand that you have many modes very close in frequency, more than your spectral resolution. However, 3 nm width is a low value for the full gain bandwidth of the dye. What do you mean for TIR ?
TIR meaning total internal reflections by cuvette walls , or residual Fabry Perot reflections as you pointed out. I would be very grateful if you could tell me as to what is a typical value for the full gain bandwidth of Rh6G
Hi Mandeep, typical FWHM of dyes is about tens of nm. As an example this measurement is around 50 nm.
http://omlc.org/spectra/PhotochemCAD/html/083.html
see references in this link for more details and measurements
As u moved from cuvette to vial, spectral narrowing disappeared at the same pump pulse energy concludes, that lasing/ narrowing is is observed because of non zero feedback obtained from parallel walls of cuvette unlike in vial. Now such lasing action can be told random lasing as per my knowledge till date.
In random lasing multiple scattering process should be involved in the lasing action, which is not happening in this case.
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