Femtosecond writing of near-surface waveguides in lithium niobate for low-loss electro-optical modulators of broadband emission

摘要: In the investigation we demonstrated technique of direct femtosecond laser writing tracks with induced refractive index at record low depth under surface lithium niobate (3-15 μm). It was shown that help proposed one can be written claddings near optical waveguides plays a key role in fabrication fast electro-optical modulators operating voltage. Fundamental problem resolved consists suppression negative factors impeding inscription depths. To prevent breakdown crystal used high numerical aperture objectives for focusing light. shown, advanced heat accumulation regime is inapplicable near-surface waveguides, and should non-thermal contrast to widespread depths tens micrometers. Inscribed were examined losses polarization properties. experimentally have such advantages over widely proton exchanged Ti-diffusion as lower (down 0.3 dB/cm) maintaining all states propagation light, which crucial development broadband ultrashort emission. Novelty results crystals. As compared previous investigations field (structures 50 um buried electrodes), obtained could simple closely adjacent on-surface electrodes.