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18:06 May-18-2009
Ricki
Appropriate laser wavelength for propagating solitons

I am currently doing research on propagation and detection of solitons using a pulsed laser source. The propagation is based on the material's response to thermoelastic stresses caused by the laser pulse's rapid heating of the material.
My question concerns the appropriate wavelength to be used for such an experiment. I have been unable to find any research papers or journal articles justifying the best wavelength to use. The papers usually just state which wavelength was used in the experiment but do indeed state the appropriate energy. I need to know if the choice of wavelength is arbitrary, or is there a specific range?

 
10:47 May-19-2009
Mark
Re: Appropriate laser wavelength for propagating solitons In Reply to Ricki at 18:06 May-18-2009 (Opening).

I am not the most experienced at this, but I'm sure at least one thing you will need to take into account is the reflectivity as a function of wavelength of your material. Since you want to work in the thermoelastic regime you will want a wavelength where absorption is high/ reflection is low, and also a relatively low energy density (you may want to deliberately de-focus or attenuate your laser beam, to avoid working in the plasma regime).

I think in the case of metals, infra red wavelengths are used for plasma-regime ultrasound because the metals reflect strongly at these wavelengths leading to effectively double energy density just above the metal surface, hence plasma formation. Therefore shorter wavelengths would be better for thermoelastic work.

Mark.

 


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