Femtosecond Laser Precipitation of Non-centrosymmetric Crystals in Glasses

摘要

Optical processes that rely on second-order nonlinear optical effects such as second harmonic generation and optical parametric amplification require the use of non-centrosymmetric crystals (NCCs). Recently it has been reported that femtosecond lasers can be used to precipitate NCCs within supersaturated glasses, forming waveguide structures . During laser writing, a combination of thermal gradients together with the laser polarization, cause the alignment of the polar axis of the NCC along the writing direction. Femtosecond precipitation of NCCs in glass has the potential to be a lower-cost alternative to other methods of achieving NCC waveguiding structures. In this study a widely used ferroelectric NCC, Lithium Niobate, was precipitated in 33LiO_2-33Nb_2O_5-34SiO_2 (mol%) (LNS) glass, forming crystalline aligned channels within the amorphous glassy matrix. The precipitated lithium niobate was characterized and the structural orientation determined. The waveguiding characteristics were measured for several conditions to determine optimal power and writing speed. This procedure was then modified to optimize the precipitated 1-D structures for photonic and holographic applications.