| With the rapid development of modern optical communication technology, thedemand of integrated optical devices with excellent performance simultaneously hasbeen urgently raised. As the most common unit in the integrated optical device, theoptical waveguide is requested not only with the excellent performance, but also withthe very short length for optical waveguide.The organic polymers are more suitable for electro-optic modulator which requestto matching between optical wave and microwave，because they have the prominentfeature of the low dielectric constant in optical properties. In addition, it has beendeveloped rapidly in optical waveguide because of its high electro-optic coefficient, lowtransmission loss and low fiber coupling loss, easy fabrication and modulation, so on.Now organic polymer optical waveguides have been applied to optical modulator,optical switch filter, attenuator, amplifier, optical connector and the performance ofoptical communication network has been improved greatly.The optical waveguides in integrated optical devices are generally the symmetryridge waveguide. When they are composition of curved waveguide, the reducing ofcurved waveguide length is restricted by radiation loss and transition loss. Theasymmetry ridge waveguide can reduce the loss because its structure is uniqueasymmetric and the outer of curved waveguide is the short core. Therefore, symmetricalridge waveguide will helps to improve obviously the transmission performance of bendwaveguide.In this thesis, the asymmetric structure in polymer ridge waveguide is proposed.The optical waveguides of Mach-Zehnder electro-optical modulator are systematicallystudied with organic polymer asymmetric ridge waveguide as the object. On the basis ofstudying deeply basic analytical methods of ridge waveguide, the relationship betweenthe performance and structure parameters of polymer ridge waveguide withasymmetry structure are analyzed in Semi-vector finite-difference beam propagationmethod (FD-BPM) and Alternating direction implicit method (ADI). The transmissioncharacteristic is systematically discussed and studied with organic polymer asymmetric ridge waveguide as the object. The research results have shown that if the symmetricbend ridge waveguide was instead with asymmetric bend ridge waveguide, the length ofbranch waveguide can reduce30%in the same transmission loss conditions.The main content in this thesis as follows:1. The relationship between structure parameters and effective refractive index forpolymer asymmetric ridge waveguide is studied. Using the semi-vector finite-differencebeam propagation method, the relationship between effective refractive index andstructure parameters of organic polymer ridge waveguide are analyzed. The asymmetricstructure is used in the ridge waveguide of organic polymer and its model is established.The results show that the effective index increased with increasing of ridge height, ridgewidth and core height. For the asymmetrical ridge waveguide the effective indexdecreased with reduction of the short side width of the core plate.2. The single-mode and cut-off conditions of fundamental mode, polarizationcharacteristic of organic polymer asymmetric ridge waveguide are studied. Thelimitations of SOI single-mode condition formula used to organic polymerridge waveguide are analyzed. Above condition and characteristic for organic polymersymmetric ridge waveguide are analyzed and studied. On the basis, that for asymmetricridge waveguide are analyzed and studied yet and both results are compared. The resultshows that both fundamental mode cut-off area and the single-mode area increased withreduction of ridge height and ridge width while the single-mode area decreases withreduction of the short side width of the core plate at a certain core height.3. The transmission characteristics of optical field for polymer bend waveguidewith asymmetric structure are studied. By applying polymer asymmetry ridgewaveguide to three different bend waveguide, sine-bend, cosine-bend and arc-bend, theloss was decreased effectively by using the deeply-etched characteristic of outer bendwaveguide. Their transmission characteristics of optical field are analyzed with thesemi-vector finite-difference beam propagation method. The results show that the lengthof bend waveguide can be reduced by30%under the same conditions of transmissionloss.4. The transmission characteristic of optical field in Mach-Zehnder electro-opticalmodulator (MZM) with polymer asymmetric ridge waveguide was studied. Using thethree branch waveguide to MZM, the characteristics and performances of MZM with symmetric and asymmetric ridge waveguide are analyzed and they are compared, theirstructure parameters are designed and optimized. The purpose of shortening the lengthof MZM is achieved.5. The bias control circuit for MZM is researched, designed and achieved. Becausethe characteristics of the basis operating point are changed with environmental impact,the control circuit is designed and achieved by novel programmable system-on-chip(PSoC) system. This circuit can control automatically the bias voltage withproportion-integral-derivative (PID) algorithm. The Printed Circuit Board (PCB) hasbeen designed and produced. The related software of algorithm and control has beencompiled. The circuit has been debugged. Finally, the LiNbO3MZM was tested.In a word, the organic polymer ridge waveguide is main object in this thesis andthe asymmetric structure is applied to polymer ridge waveguide. Combining theadvantage of both organic polymer and asymmetric ridge waveguide, the properties ofbend waveguide has been well raised and the work has some reference value. In future,the study centers on part of many kinds of organic polymers and the whole design ofMZM deeply, so that provide the basis for raising the performance of optical integrateddevices. |
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