Bias-free electro-optic polymer-based two-section Y-branch waveguide modulator with 22 dB linearity enhancement

A bias-free two-section Y-branch directional coupler modulator with high linearity based on domain-inverted modulation is fabricated and tested. $25\mathrm{wt.}\%$ AJLS102/APC is used as an active core layer with an experimentally confirmed device $r_{33}$ value of $56\mathrm{pm}∕\mathrm{V}$ at $1.59\mu \mathrm{m}$. The fabricated device shows an extinction voltage of $4\mathrm{V}$. A two-tone test is performed to demonstrate $64\mathrm{dB}$ distortion suppression at 25% modulation depth, which is $22\mathrm{dB}$ higher than a conventional Mach–Zehnder modulator.