i think your laser Fre must be lower than plasma Fre .w(plasma)

Inverse Bremsstrahlung may be dominant but there are also many other interesting process resulting from collisionless transport. In many cases the parameter called critical density is important and can introduce resonant density or parametric processess for wavelengths chararacteristic for this density.

The subject is quite broad and you needn't study it very extensively if you want to focus on your specific experimental needs.

For sure you can go through the contents of eg. W.L Kruger, “The physics of laser plasma interaction”, Addison-Wesley, Reading, MA, (1988) and find exactly what you need.

Thank you for your answers..

Density and temperature of the plasma are the main parameters to consider, in the past we implemented some very simple models about this:

Laser Ablation of Metals: A 3D Process Simulation for Industrial Applications

Giovanni Tani, Leonardo Orazi, Alessandro Fortunato and Gabriele Cuccolini

J. Manuf. Sci. Eng. 130(3), 031111 (May 12, 2008) (11 pages)

doi:10.1115/1.2917326

G. TANI, L. ORAZI, A. FORTUNATO, G. CUCCOLINI (2007). The influence of plasma plume in laser milling for mold manufacturing. JOURNAL OF LASER MICRO NANOENGINEERING, vol. 2, p. 225-229, ISSN: 1880-0688

All answers are quite interesting and correct, I summarize them as below :

- Electron density and plasma temperature: Those plasma chracteristics may be measured by means of plasma characteristic emission spectra based on Stark and Botzmann eqs.

- Is plasma dilute or dense? Interaction of light with neutral species ( excitation and photo-ionization PI).

- IB absorption and its dependence on square wavelength of incident beam.

- IB absorption and its dependence on plasma density.

- Plasma frequency, wether incident laser frequency is lower or higher than plasma fequency: light can propogate or it is reflected or absorbed in plasma according to dispersion eq.

- Temporal scale : Is the incident laser beam pulsed or CW? and what is the plasma duration?

Furthermore:

Plasma freq is proportional to electron density of plasma.

Plasma absorption coefficient is roughly proprtional to square of electron density.

Therefore, for dense plasma, the absorption rate is much greater than dilute one.

Cold plasma: electron-ion collision rate is much smaller that laser freq.

Hot plasma: e-i collision rate is comparable to laser freq.

Dispersion eq: kc=(w^2-wpl^2)^1/2 ,then:

w > wpl then kc>0 =>laser beam propagares through plasma.

w = wpl then kc=0 ,no more energy heats plasma, laser beam reflection=>Ncit

w < wpl then kc is the imaginary component of refraction index is significant => laser beam is absorbed by plasma (mainly by IB process and other mecanisms).Moreover,

multiple photon scattering and backscattering become dominant when plasma density scales up and wpl (plasma frequency) is greater than laser freq.