Fully planar proton-exchanged lithium niobate waveguides with grating taps

A two-step proton-exchange process to produce waveguides and gratings in lithium niobate is described. In both steps, mixtures of lithium benzoate and benzoic acid are used. The fabricated components are characterized at 0.633 and 0.422 µm. In particular, we observe that the light intensity diffracted into the air by the grating is ~0.5% of that in the waveguide.