Subsurface disorder and electro-optical properties of proton-exchanged LiNbO3 waveguides produced by different techniques

It has been established, that proton-exchanged LiNbO3 waveguides have a marked subsurface layer with structural disorder inducing degradation of electro-optical properties of these waveguides. At the same time, such a subsurface disorder is found to be less pronounced in soft proton-exchanged (SPE) waveguides in comparison with annealed proton-exchanged (APE) ones. The experimental samples of phase modulators fabricated by SPE technique exhibit a better electro-optical efficiency compared to the LiNbO3 modulators produced by the standard and improved APE techniques

Nanoscale characterization of β-phase HxLi1−xNbO3 layers by piezoresponse force microscopy

We investigate a non-destructive approach for the characterization of proton exchanged layers in LiNbO3 with sub-micrometric resolution by means of piezoresponse force microscopy (PFM). Through systematic analyses, we identify a clear correlation between optical measurements on the extraordinary refractive index and PFM measurements on the piezoelectric d 33 coefficient. Furthermore, we quantify the reduction of the latter induced by proton exchange as 83 ± 2% and 68 ± 3% of the LiNbO3 value, for undoped and 5 mol. % MgO-doped substrates, respectively.Science Foundation IrelandCOST action MP0702Swedish Research CouncilADOPT Linnaeus Centre for Advanced Optics and Photonics, Stockhol

Phase composition and electro-optic properties of channel proton-exchanged LiNbO3 waveguides

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