Controllable Wide-Angle Lithium Niobate Polarization Splitter with Sidewall-Extended Electrodes
Date Issued
2009
Date
2009
Author(s)
Lin, Chia-Wei
Abstract
A controllable Y-branch polarization splitter is successfully fabricated and demonstrated for the first time. The proposed device is an integration of a phase shifter, polarization converter, and polarization splitter on one chip. This device is to split a randomly polarized optical input into TE and TM outputs with arbitrary power ratio between these two polarizations.n order to design a compact device size, the simplified coherently coupled bent structure is applied to design the Y-branch polarization splitter with an effective full branching angle of 1.5?. This angle is three times larger than that of conventional Y-branch polarization splitter fabricated on lithium niobate. With this branch angle the device size can be reduced by 52% when the separation between TE and TM output branches is 175 µm. Moreover, the polarization splitter with this wide angle bent structure will still satisfy the mode sorting effect and possess more than 25 dB polarization extinction ratios for both TE and TM modes. To reduce the applied voltage of the polarization converter, the sidewall-extended electrodes are applied to increase the overlap integral of the converter. Experiment results show only 54V is needed to convert one single polarization state into the other, and the applied voltage can be reduced 52% than that with the conventional ridge-electrode structure.inally, a phase shifter is integrated with a polarization converter with sidewall-extended electrodes, and a wide angle polarization splitter with simplified coherently coupled bent waveguide to form a 16 mm long controllable wide-angle polarization splitter. As a 45? linearly polarized input is lunched to this controllable polarization splitter, arbitrary power ration between two split polarization outputs can be achieved by biasing the phase shifter at proper voltage and applying a correct voltage to the converter. At a propoer bias, the single polarization output can be achieved by applying 27V to the converter. However, the same 45? linearly polarized input of the variable TE-TM polarization splitter without phase shifter can not be transferred to single polarization output. Moreover, experimental results show the proposed controllable polarization splitter can be used to transfer and split randomly polarized input to any output power ratio between TE and TM modes with suitable applied voltages for the phase shifter and the polarization converter.
Subjects
lithium noibate optical waveguide
polarization controller
polarization splitter
polarization converter
Type
thesis
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