Ultra-broad-band LiNbO3 electro-optic modulators with novel complex electrode

The characterization of Z-cut LiNbO3 optical modulators with novel complex electrode are discussed by using the finite-element method (FEM) and studied experimentally in this paper. The calculation results show that the configuration of the electrode can realize microwave-optical velocity match easily and reduce microwave electrode losses drastically, so the modulators with such electrode are candidate devices for future ultra-high-speed optical fiber transmission system. The traveling wave electrode is consists of upper and lower parts. Because the thickness of the hot electrode can be thicker, the microwave attenuation coefficient of the traveling-wave electrode alpha(o) is able to be less than 0.35 dB/(cm GHz(1/2)). The configurations of the electrode are optimized by criteria of the ratio of 3dB optical bandwidth to drive power. The results of optimization show that the properties of the modulators can be improved by increasing the electrode gaps. An electro-optic modulator with bandwidth 100 GHz, half wave voltage 6 V is designed. The modulator is being fabricated in our laboratory. Some experimental results of the traveling-wave electrode are obtained. The characteristic of low microwave transmission loss of the electrode is demonstrated. The attenuation coefficient alpha(o) measured by microwave network analyzer is as low as 0.35 dB/(cm GHz(1/2)).