Multiplexed Output Based On The Organic Polymer Photonic Rf Phase Shifter

With the widely applications of optical phased array antenna in the military sectors, a lot of research groups around the world have been paying more attention to the photonic radio frequency (RF) phase shifters, which are playing an important role in the optical phased array antenna. In recent years, optoelectronic devices fabricated by organic polymers, becoming more significant in the field of photonics, are widely concerned. So we demonstrate an integrated photonic RF phase shifter in a novel nonlinear optical polymer.At first, the research significance and progress of photonic RF phase shifters and nonlinear optical polymers are introduced simply in this dissertation. And then, the characteristic equations of TE mode and TM mode in a three-layer slab optical waveguide deduced from Maxwell equations and the operation principle of effective index method and variational effective index method are described. The analysis method discussed in the structures of the optical waveguides is based on the finite difference beam propagation method (FD-BPM). By the effective index method, the width of rib waveguide for an operating wavelength of1.55μm is obtained5μm at the condition of single-mode propagation, in which the thickness of core layer and rib waveguide is1.5μm and0.2μm respectively. The simulated result of optical waveguide got by OptiBPM.For the minimum device length and insertion loss, the raised-sine S-bend waveguides structures have been used in all the Y-branch sections. The simulation of optical waveguides of the device by OptiBPM exhibited the excess optical loss, crosstalk at the optical waveguide crossings and the imbalance power splitting at output ports of the Y-branch. The reason for the imbalance power splitting is the distortion of the field outgoing from the bends. So a novel bend called the matched bend for the optimum design of the bent sections of integrated optics components is introduced.In Chapter3, the operation principle of primitive photonic RF phase shifter was described. The simulated result shows that the calculated RF phase varies almost linearly with the control voltage up to110°and the RF power exhibits fluctuation of approximately15dB as the control voltage is tuned over2Vπ, which is very undesirable for system applications. Investigation shows that most of the detrimental effects are caused by the presence of the carrier signal from optical SSB modulator unit. Having recognized the origin of the detrimental effects, a simple solution under small signal operation has been introduced. This novel architecture inserts an additional arm called the balancing arm in the inner MZ, which is intended to suppress the carrier signal from the optical SSB modulator unit. The power splits at Y-branch are1:a for the balancing arm and1:1for the others. The calculated RF power does not vary at all and the RF phase shift is highly linear with respect to the control voltage. In order to control the splitting ratio a and reduce the additional DC biases, the second and third Y-branch can be replaced by the multimode interference (MMI) splitter. For the miniature and high performance, it is favourable to integrate multiple phase shifters in a single ship. The modulated optical output from the balanced optical SSB modulator is split into two branches and combined with the two outputs from the optical phase shifter, which is called two outputs photonic RF phase shifter. The simulated results of the optical waveguide of the device by OptiBPM exhibit that the optical loss of two outputs of the device are7.30dB and7.42dB respectively, and the excess optical loss and the crosstalk are0.56dB and21.55dB respectively at the optical waveguide crossings section. Further more, the simulated of the electro-optic interaction area10000μm of the optical waveguide shows that the optical field phase shift is236°as the control voltage is8V. The electrode system of photonic RF phase shifter is single microstrip line.By the optical integrated circuits technology, the photonic RF phase shifter is fabricated, including thermal vapor deposition, spin coating, photolithography, etching, reactive ion etching (RIE), and corona poling, et al. The device size of the two outputs photonic RF phase shifter is4cm×0.5cm.It is believed that the implementation of the photonic RF phase shifters in military sectors will greatly enhance the performances of military equipment in future.