Effects of parasitic modes in high-speed LiNbO(3) optical modulators

The characteristics of RF parasitic modes and the methods to suppress leakage phenomena in LiNbO(3) optical modulators were studied. The high frequency RF power transmission characteristics were simulated and experimented in the respects of LiNbO(3) wafer thickness, the kind of material contacting the back surface of the modulator chip, the gap and width of the CPW (co-planar waveguide) electrodes. An appropriate RF electrode geometry, to minimize coupling efficiency between co-planar waveguide and substrate mode, is proposed. Experimental results prove that the approaches made in this work are effective for broadening of modulation bandwidth.