Lithium Niobate <sub> 3 </ Sub> Waveguide Electro-optical A / D Converter Technology

In this paper, the general principles and progress of high-speed electro-optic ADCs (analog-to-digital converters) were reviewed. The superiority over electronic ADC, the significance and the prospect of its applications were also introduced in details. The four mainly techniques of electro-optic ADC were discussed in brief. The fabrications and performances of the electro-optic ADC based on the four mainly techniques were described, analyzed and compared. The integrated optical wave-guide ADC was thought as one of the most promising trends of the electro-optic ADC. Then, four aspects of our works were discussed in detail. Firstly, after the analysis and the comparing the optical ADC based on phase-encoded optical sampling and the electro-optic ADC based on OTDM (optical time division multiplexing), OWDM (optical wavelength division multiplexing) and photonic time stretched, the phase-encoded optical sampling technique was anatomized. A novel technique, doubling the modulation voltage of M-Z (Mach-Zehnder) interferometer arrays, was proposed. Its function characteristics were theoretically analyzed and compared with Taylor's technique of doubling the modulation electrode length. Secondly, the overall design of our project was given. With the BPM (Beam Propagation Method) and the Effective Index Method, the center parts of our project, which includ the wave-guide, the Y-junction splitter and the M-Z interferometer arrays, were designed. The vital structural parameters were given. At last, the template of the wave-guide and electrode was accomplished according to the structural parameters. In addition, the detecting electrical circuit was designed and set up. Thirdly, since the M-Z interferometer arrays were vital part of our project and the quality of the wave-guide has much more influence on the performance of the whole module, a lot of attentions have been paid to the proton-exchange procedure on the X-cut Y propagation lithium niobate substrate, and ameliorated the normal procedure and apparatus in practice. In the experiments of proton-exchange in pure benzoic acid, a new phenomenon affecting the quality of wave-guide has been observed, concluded and explained, and a solution was found in experiments. Finally, a two bits electro-optic ADC, constituted with an optical fiber splitter, two similar lithium niobate M-Z modulators linked with the optical fiber splitter and two photodiodes, was upbuilded in experiments. The modulation voltages of the two...