摘要(英) |
In this study, the structure of asymmetric adiabatic coupler (AAC) is designed using the concept of Stimulated Raman Adiabatic Passage (STIRAP), and applied it on the lithium niobate(LiNbO3) with the titanium diffused waveguides to become a polarization beam splitter. We designed the structure into two parts to split TE and TM polarization. Our goal is to achieve the broadband polarization beam splitter by using a two-stage structure to separate two different polarized lights. Before the fabrication process, we do the simulation part. In the simulation process, first step we use 1550 nm as the center wavelength to simulate TE and TM polarization in different structures. Second step, based on our previous simulation, we apply an adiabaticity engineering method to optimize the waveguide system configuration to achieve a broadband polarization beam splitter. Finally, we use a TE-polarized 775 nm laser as the pump to examine the structure to make sure the pump will be spatially filtered from the cross-polarized signal and idler. Furthermore, we fabricated such an AAC chip to measure the experimental result.
We used the standard lithography process and titanium diffusion process to fabricate the AAC chip in a 51 mm long, 25 mm wide, and 0.5 mm thick LiNbO3 crystal.
In the measurement result, we had a good-fitting result with the simulation process. It can be found a bandwidth of >120 nm can be achieved in this unique Ti:LiNbO3 polarization beam splitter at a power splitting ratio of >95% for both polarization modes, which is to the best of our knowledge the broadest bandwidth ever reported in integrated optical LiNbO3 polarization beam splitters. |
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