Hybrid cross-linkable polymer/sol-gel waveguide modulators with 0.65V half wave voltage at 1550nm

The authors report on a hybrid cross-linked electro-optic (EO) polymer/sol-gel Mach-Zehnder waveguide modulator with a half wave voltage $\left(V_{\pi }\right)$ of $0.65\mathrm{V}$ at $1550\mathrm{nm}$ . The low $V_{\pi }$ was achieved by a design that (1) combines both physical vertical tapers in the sol-gel core and photobleached index tapers in the EO polymer and (2) reduces the thickness of the device to $8\mu \mathrm{m}$ . These combined physical and index tapers result in improved optical mode confinement in the EO polymer with low adiabatic optical transition loss. The reduced thickness results in a larger field across the EO polymer for the same voltage, enabling a lower $V_{\pi }$ .