Single-drive X-cut thin-sheet LiNbO3 optical modulator with chirp adjusted using asymmetric CPW electrode

The authors propose a prechirped X-cut thin-sheet lithium niobate modulator. In this modulator, the α-chirp characteristic can be adjusted in the range of 0 to 0.8 by making coplanar waveguide electrodes asymmetric. In addition, a low-driving-voltage operation is achieved to make use of the thin-sheet structure without a SiO₂ buffer layer. We fabricated such a modulator with an α-chirp parameter of 0.65, a low half-wave voltage of 2.5 V, and a large bandwidth of 20 GHz. We also confirmed 10 Gb/s error-free transmission over an 80 km normal fiber (1.3 μm zero-dispersion fiber) at a wavelength of 1.55 μm by utilizing the modulator.