| This thesis investigates InP-based multiple quantum well electroabsorption modulator theoretically and experimentally. As is widely recognized, the optical modulator is a key and indispensable device in optical communication system. Travelling-wave modulators on Ⅲ-Ⅴ are widely studied in many earily works, the substrate of which has been widen from GaAs to inP, and active layer from bulk material to quantum well, quantum line, and quantum dot, with the soaring need for application and the maturing of material growth.The main research results include:Firstly, InP-based InGaAsP material parameters are modified, and then applied to the following analysis. The bingding energy of light and heavy exciton in InGaAsP quantum well is computed to be 5meV and 2.7meV, respectively. The result is compared with the result of GaAs to verify the correctness of this result. The electroabsorption in lattice-match material is obviously polarization dependable. When appropriate strain-compensated multiple quantum wells are adopted, the transition enery of light-hole and heavy-hole exciton under different electric field is nearly equal, and the electroabsorption of it is polarization independable. For 1570nm indent light, the difference of dependency is less than 2.5dB, and the peak-peak modulation voltage is about 3.2 V.Secondly, electroabsorption modulator optical waveguide is investigated to realize poloarision independable operation. One of the figures of merit, which cover many parameters, is design guidelines. The device length is selected to be 200μm as a tradeoff between contrast ratio and microwave properties. By making the core thicker than quantum well absorption layer, the device capacitance is smaller and the bandwidth is extended. When the mode size of fiber is reduced to around 2μm in diameter, width of ridge little affects the couple efficiency between the modulator and the optical fiber. Thicker p-clading layer, about 1.4μm, is selected to avoid metal electrode influence on different mode absorption. And the figure of merit shows that the large change of field-induced absorption coefficient is important for the device performance. For the device designed, the contrast ratio is about 20dB, and the insert loss is about 10dB. When strain-compensated MQW is applied in absorption layer the saturation power of modulator will increase.Thirdly, microwave properties are analysized by method of line. It is more suitable to use coplanar waceguide electrode than coplanar strip electrode for high-speedmodulation. Meanwhile, PIN device structure has lower leak current than Schottky structure, so PIN structure is chosen. Toward the coplanar waveguide on ridge waveguide, the additional transformation matrice, describing the material unhomogeneity, is introduced. Furthermore the finite electrode thickness is also considered to simulate the physical device. To save computing time, the microwave properties at 50GHz signal is first simulate to narrow the parameters range, and then wide frequency signal is simulate to have more detailed device information. In the end, with appropriate approximation, and by low terminal resistance, the frequency response is acquired. The results show that the device has the bandwidth of 70GHz.Finally, the fabrication process of electroabsorption modulator is researched, thus it is approved that the whole process procedure could be fulfilled. Also, the Mach-Zehnder modulator is fabricated and then the S parameters are measured with Vector Network Analyzer. As is shown in the testing results, the frequency response keeps no evident drop in the range of 2.5~20GHz. Those results are also argued in this thesis. Then, having conducted the research work on electroabsorption modulator and Mach-Zehner modulator, we compared and contrasted these two kinds of modulator in order to point out their character, defects and virtues.
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