Hybrid electro-optic polymer/sol–gel waveguide modulator fabricated by all-wet etching process

A simple all-wet-etch process fabricates a hybrid electro-optic-polymer (EOP)/sol–gel waveguide modulator, confining the EOP laterally in the sol–gel overcladding. The structure enables an adiabatic transition between the passive sol–gel waveguides and the active EOP overlayers without lateral radiation. Intensity is confined well in a 0.9-μm-thick EOP overlayer, resulting in a low half-wave voltage ${\mathrm{(V}}_{\pi })$ due to the larger overlap integral. This lateral confinement technique allowed the reduction of $V_{\pi }$ (at 1550 nm) by a factor of 4.