Multiphoton and plasma absorption measurements in CaF₂ and UV fused silica at 473 nm

Abstract

Transmission versus intensity in 100 μm CaF2 and UV fused silica samples at a wavelength of 473 nm for different durations of the initial pulse was studied. Fitting the experimental data with a model based on the solution of the nonlinear Schrödinger equation and taking into account multiphoton absorption and absorption by the plasma, as well as the Kerr nonlinearity, diffraction and dispersion of the medium, made it possible to obtain the values of multiphoton (k-number of photons) σk and plasma absorption (inverse bremsstrahlung) σ cross sections. The obtained values are σ 4 = 2.5 × 10−117 cm8 s3, σ = 3.6 × 10−18 cm2 for CaF2 and σ 4 = 4.4 × 10−116 cm8 s3, σ = 3 × 10−18 cm2 for UV fused silica.

An Experimental Study of Multiphoton Ionization in Fused Silica at IR and Visible Wavelengths

“…Finally, the β n values obtained from Figures 2 and 3, taking into account Expression (8), allow us to obtain the multiphoton absorption cross-sections in the cases of four-and eighphoton ionization: We note that very similar four-photon cross-sections for the fused silica were measured for the 473 nm laser wavelength σ (4) = 4.4 × 10 −116 cm 8 s 3 [27]. Although the difference in the cross-sections seems to be large, due to the high nonlinearly of the process, it results in fairly close data for the multiphoton electron production.…”