| Due to the advantages of frequency bandwidth, low loss, large capacity, high reliability, light weight, small size and no short circuit, optical fiber communication has rapidly become the main form of information transmission nowadays. Particularly the high-speed optical transmission systems have been developed rapidly in recent years. The requirements of bandwidth are getting higher and higher. It is a key device for high-speed and long-distance communication. High-speed electro-optical modulator has become a hot spot in recent years. The organic polymer based on the nonlinear optical has been used as a new type of photoelectron materials. It has great research and development space in the field of integrated optics. Compared with the inorganic materials (LiNbO3,KH2PO4), these materials have a lower microwave dielectric constant, a higher electro-optic coefficient as well as good compatibility of preparation. It is applicable to the production of high-speed electro-optical modulator. Moreover, organic polymers can produce the electro-optical modulator with low half-wave voltage, high-bandwidth.The electro-optic modulator is one type of the modulation devices to modulate transmission beam realized by the characteristic, which is influenced by refraction index of electro-field of electro-optic materials. According to the different structures of the devices, electro-optic modulator can be divided into two types: electro-optical modulator and waveguide transmission electro-optical modulator. Waveguide type EO-modulator has high-speed, chirp noise of wavelength is zero theoretically. It almost does not limited by the fiber dispersion. It has been used widely home and abroad. There are many types of waveguide transmission electro-optical modulators. Mach-Zehnder type (M-Z) electro-optic modulator is a more practical one. The M-Z modulator uses of a traveling wave electrodes. It has the advantages of high-speed modulate rate and little chirp noise of wavelengths. It has become the important parts in optical fiber communication systems.Firstly, the kinds of electro-optical modulator and the research progress of organic polymer electro-optic modulator in recent years are described here in detail. And it is discovered that the research progress of organic polymer electro-optic modulator is developing in depth gradually and its indexes are incessantly enhanced. It becomes a hotspot and will be a good prospect for future research. According to the request of electro-optical modulator performance index the organic polymer materials have some advantages:1) Low dielectric constant, which provides high-frequency response and speed matching between light and microwave of broadband traveling wave structure;2) Higher electro-optic coefficient, which makes it more accessible to obtain a low half-wave voltage and very beneficial to prepare the modulator.3) Can form good films on different substrates, and can execute multi-layer structure. They have a better compatibility of preparation. These all provide a convenient condition to integrate polymer modulator with semiconductor devices. Thus it can be seen that organic polarized polymer electro-optic modulator has a good development prospect.Secondly, the basic principle of polarized polymer electro-optic modulator has been described. Not only the electro-optic effect has been introduced in detail, but also the work principles of two basic types of polymer electro-optic modulator (M-Z and directional coupler) have been analyzed. Due to the M-Z electro-optic modulator uses a simple mathematical model. And the full switching effect should be obtained to the directional coupler. The technological allowance error to the length of coupled waveguide section is very small. It should require higher requirements of the technological level in the actual preparation progress. Therefore, we can conclude that: the preparation progress of M-Z modulator is easier than that of directional coupler. Then the theory of M-Z modulator has been analyzed. The parameters which have a good relationship between their performances, such as the modulation bandwidth, the driving power of unit bandwidth, modulation depth and insertion loss are introduced. At the same time, the electrode structure of M-Z electro-optical modulator is analyzed, including the interaction area, the transition zone and the input and output areas.In theory, microwave characteristic impedance at electrode system interaction zone has been analyzed. The effect of the centre electrode width, the clearance between center electrode and the ground electrode and the thickness of the electrode to the characteristic impedance also has been studied. After study, it shows that, under the condition of ensuring the preparation processes of electrode unchanged, the microwave characteristic impedance of electrode system increases with the width of centre electrode and the interval of electrode. But for the latter the scope of effect, it is much smaller, due to the limitation of process conditions, and for the thickness of electrode too. The microwave electrode impedance parameters have been calculated using Advanced Design System. The overlap integral factor has been introduced. At the same time, the relationship between drive voltage and electrode parameters of devices with CPW traveling-wave has been analyzed.Experimentally, two methods (Corrosion and lift-off) to prepare polymer electro-optic modulator electrode system have been introduced in detail. The process of prepare polymer electro-optic modulator electrode has been created and developed, lift-off has been analyzed, and a comprehensive process has been summed up. At the same time, some problems have been already solved, as follows: serious side etch in etching method, bad adhesion of metal film, imprecise exposure time in dissection method, lower success rate in removing photo resist .This part of the experimental work has important reference values to the relative future work.?... |
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