| Optical phased array technology is the modern radar technology that combines both microwave technology and photonics technology for controlling a scanning beam of the antenna arrays. This technology realized the advantage complementary between microwave technology and photonics technology, and So, it has unique advantages in upgrading radar scanning speed, working frequency, instantaneous bandwidth and scanning accuracy and it plays an important role in satellite communications, radio astronomy, space and air control .Microwave photonic phase shifter (MWPPS)is widely concerned and researched as the key device of controlling beam-forming, As for the domestic's research of this device is in the theory of state for a long time, only a separation device constructed phase shifter is occasionally reported. The abroad in this field have already begun the study of integrated devices. Our research is beginning just based on this background. We fabricate MWPPS by using SOI, which has good electrical and optical characteristics, and by using Planar Light wave Circuit (PLC) technology. Because of its processes fully compatible with silicon-based CMOS technology, the development of low-cost photonic integrated circuit is one of the important trends, and therefore it is expected to realize the true sense of monolithic integration and give a fundamental resolution of device performance instability, bulky, big weight, high production costs. In addition, the enhancement of accuracy in phase-shifting, reduction of power consumption is also an important task in this issue.This dissertation has a full basic research of MWPPS in the initial phase of the project. By using vector sum technology as the basic guiding ideas and SOI ridge waveguide material as device materials. Coupling based thermo-optical variable Optical Attenuator was used as the basic unit of the amplitude attenuation. These constitute the innovative and unique of the device. In addition, of the detailed design of the device and optimization to every parameter in this paper constitutes a bright spot of MWPPS's theoretical design:This paper firstly resolves the problems of basic structure and function realization. Not like the traditional vector sum analysis, we strictly derivate and demonstrate the phase-shifting function of the devices by combing the basic vector ideas with the carrier modulation, as well we achieve the design conditions for realizing the phase-shift function.SOI rib waveguide can achieve single-mode transmission with great cross-section size .By using Effective refractive Index Method (EIM),we analysis the mode characteristics and obtain the full single-mode conditions of SOI rib waveguide. The experimental results reported by others prove the full single-mode conditions are right. Then, we make use of the finite difference method beam propagation method (FD-BPM) to analysis the bending loss characteristics of the semi-circular SOI rib waveguide delay lines .Combing with tolerance analysis, the optimum parameters of the delay line was obtained as follow: H = 5μm, w = 3μm, h = 2.7μm, R> 13mm and the semicircle delay line's bending loss Lbend180<0.1dB.Throughout the photonic integrated circuit, in order to achieve light wave's splitting, combing and changing of propagation direction, the use of curved waveguide is inevitable. Cosine-type curved SOI rib waveguide was used to form Y branches under the guidance of the mode field matching. The principles of designing large and small angle Y-shaped beam splitter were obtained, and then 1×4 splitter, 4×1 combiner are designed by using cascaded Y-branch. Finally, FD-BPM is used to simulate1×4 splitter and 4×1 combiner. The results show that the average additional loss of EL<0.45dB, output imbalance of IF <0.1dB.Finally, the amplitude attenuation units are designed. We first use the three waveguides direct-coupled structure to build variable optical attenuator (DC-VOA)by using Thermo-optic effect of silicon. The length of coupled area of three-waveguide structure decreases 2 times than that of double-waveguide structure, which plays an important role in decreasing device's size. Here, we use finite element analysis software (FEM: ANSYS Inc9.0) to analysis the thermal response and the temperature distribution. Simulation result indicates that heat-guide layer can significantly increase temperature difference between inner rib area and external rib area. Scale factorαis 0.6.On the other hand, The tolerance analysis indicates that the average temperature variationΔT =350C can make the RI change of inner rib area and external rib area is 0.17% and 0.1% respectively, which guarantees the dynamic attenuation is more than 35 dB.Based on the previous theoretical analysis and optimization, we have been obtained the reasonable parameters of the device,Which provides a reliable theoretical basis for the latter experiment work. |
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