Control of femtosecond laser written waveguides in silica glass

Quantitative estimate of fs-laser induced refractive index changes in the bulk of various transparent materials

“…Qualitatively, a negative ∆n of high amplitude may be explained by the observations of Canning et al, 17 who reported the onset of micropores upon femtosecond laser irradiation. The ∆n observed in the filamentary region is consistent with the measurements of Saliminia et al 18 who investigated waveguide writing relying on filamentation in a-SiO 2 .…”

Femtosecond filamentation in transparent media

“…82, the energy threshold for optical breakdown in fused silica is lower than the filamentation (supercontinuum) threshold for short focal lengths while filamentation can occur below the threshold for optical breakdown for long focal lengths. From the threshold map of pulse energy as a function of the focal length for optical breakdown, single and multiple filamentation, Nguyen et al (2006) have shown that waveguides can be written in fused silica at 800 nm in the filamentation and optical breakdown regimes. The authors interpreted the smooth index change as a densification of the material by using Raman spectroscopy and stress birefringence measurements .…”

The fabrication of circular cross-section waveguide in two dimensions with a dynamical slit

“…Then diffraction method has been proposed [16]. The writing of circular cross section waveguide has been demonstrated in simulation and experiment with a 12 aspect ratio, which is bigger than most experimental results so far [17,18] if neglecting the material differ ence and nonlinear effects during writing a waveguide with femtosecond laser. In spite of this, diffraction theory is an accurate method to this problem, just need special algorithm to get high precise solution.…”