Difraction grating written inside/on of Lithium Niobate crystals by means of femtosecond laser pulses

: G.A. TORCHIA, C. MÉNDEZ, J.R. VÁZQUEZ DE ALDANA, D. DELGADO, I ARIAS AND L. ROSO

Estrasburgo

Congreso; Photonics Europe; 2006

This work deals on the fabrication process of diffraction gratings made on Lithium Niobate substrates by means of focusing femtosecond laser pulses. The main optical features of these photonic structures are presented in this paper. As it was expected the relief gratings showed high diffraction efficiency in accordance to the index modulated profile of the crystal-air border resulting in this kind of diffractive structure. On the other hand, for the inside grating a higher diffraction efficiency for the first orders were found, however the overall diffraction efficiency was found to be similar to that obtained for the ablation structures made in this work; this result suggests that the index increment in the inside grooves should be very important. The thermal stability of these structures is also studied and discussed in this paper. It is found that for the relief gratings the diffraction efficiency is temperature independent up to 400 ºC degrees, while for the inside gratings a slight decrease on diffraction efficiency was observed after making a thermal annealing at 400º C during two hours. The grating fabrication method presented in this work can be a powerful tool for development of several photonic devices made inside/ on Lithium Niobate by using femtosecond laser writing by means of the one step process.one step process.