Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

摘要

A novel method to produce optical waveguides is demonstrated for lithium niobate (LiNbO3). It is based on electronic excitation damage by swift ions, i.e., with energies at approximately I MeV/amu or above. The new technique uses high-energy medium-mass ions, such as Cl, with electronic stopping powers above the threshold value for amorphization (5-6 keVm), reaching the maximum value a few micrometers inside the crystal. At the ultralow fluence regime (10(12)-10(13) cm(-2)) an effective nanostructured medium is obtained that behaves as an optical waveguide where light propagates transversally to the amorphous nanotracks created by every single impact. The method implies a reduction of 4 orders of magnitude with respect to He implantation. The optical waveguides present reasonable losses (similar to 10 dB/cm) and significant second-harmonic generation (SHG) and electro-optic (EO) responses (> 50% bulk) for the lowest fluences. (c) 2007 Optical Society of America.