Lithium Niobate Polarization Splitter with Zinc-Nickel-Gallium Codiffused Waveguide and Sidewall Extended Electrodes
Date Issued
2012
Date
2012
Author(s)
Huang, Chih-Fan
Abstract
Controllable polarization splitters with Zn-Ni diffusion and Ga diffusion optical waveguides are successfully fabricated on Z-cut LiNbO3 substrates. The basic structure of the proposed polarization splitter is an asymmetrical Y-branch. Both TE and TM modes are supported in the input waveguide branch fabricated by Zn-Ni diffusion. In particular, the input waveguide branch is fabricated on a ridge structure with finger-type electrodes to modulate the polarizations. In the output section, only TE modes are supported in the straight waveguide fabricated by another Zn-Ni diffusion, whereas only TM modes are supported in the bent waveguide fabricated by Ga diffusion.
Though three kinds of metal with various thicknesses are deposited, only one diffusion step is needed, instead of two or more diffusion steps as used in previous works. Thus, the fabrication process can be greatly simplified.
Experimental results show, the extinction ratios are 27.8dB and 24.4dB for the TE and TM modes at 1.55μm wavelengh, which are good enough for practical applications (13dB).
To study the of tunabilities of splitters, finger type electrodes are designed and fabricated in this work, sidewall-extended and conventional electrodes with the same ridge depth and electrodes gap are compared. Experimental results show the driving voltage of splitter with sidewall-extended finger type electrodes is 41% reduced, less than those without.
Finally, polarization splitters on ridges of the depth 6μm with sidewall-extended electrodes are fabricated for demonstration. Measured results show polarization states can be completely converted by an applied voltage of 47V, which is 12.9% less than those reported.
Subjects
Lithium Niobate
Integrated Optics
Polarization Splitter
Type
thesis
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