Ultraviolet laser irradiation of a lithium niobate +z polar surface enables the production of ridge waveguides. Ultraviolet laser induced inhibition of poling is used to define an inverted domain pattern which transforms into a ridge structure by differential etching in hydrofluoric acid. The laser irradiation step also induces a refractive index change that provides the vertical confinement within the ridge structure. Furthermore, it was observed that poling-inhibition results in a significant enhancement of the refractive index contrast between the bulk crystal and the ultraviolet irradiated tracks.
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Sones et al. (2010) studied this question.
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