Stress field after femtosecond laser interaction with Nd3+ doped Mg : LiNbO3 crystals for waveguides fabrication

M. R. TEJERINA; G.A. TORCHIA

Conferencia; Conference on Laser Ablation (COLA); 2011

Laser writing with femtosecond (fs) pulses in last years represents an importtool for the fabrication of several optical circuits by means of a fast, low cost and simpleway that can be extended to a large number of materials (i.e. glasses and crystals) aspotential candidates to develop new photonic integrated devices [1-2]. As it was welldetermined by different authors, the stress field obtained from the laser interaction isthe main cause for the waveguide formation where compressed and tensile regions,surrounding to laser tracks, are obtained [4-5].The fs-laser pulses residual stress control is the key to obtain higherperformance guiding structures for photonic applications (i.e. lower propagation lossesand higher refractive index contrast). In this sense, we have developed a numericalmethod based on Finite Element (FE) to estimate the stress field of this phenomenon inseveral materials. This method takes into account the material constitutive relationaccording to the crystal’s orientation. A mechanical expansion is introduced in the focalplane to simulate laser interaction at intensities above the optical breakdown threshold.As it is well known, from the stress field, the refractive index can be retrieved. In thiswork, the mentioned method was implemented to analize type II guiding structuresgenerated in x-cut Lithium Niobate crystals by fs writing under double line approach.