Abstract
A novel ultra-short polarization beam splitter (PBS) based on a bent directional coupler is proposed by utilizing the evanescent coupling between two bent optical waveguides with different core widths. For the bent directional coupler, there is a significant phase-mismatch for TE polarization while the phase-matching condition is satisfied for TM polarization. Therefore, the TM polarized light can be coupled from the narrow input waveguide to the adjacent wide waveguide while the TE polarization goes through the coupling region without significant coupling. An ultra-short (<10 μm-long) PBS is designed based on silicon-on-insulator nanowires and the length of the bent coupling region is as small as 4.5 μm while the gap width is chosen as 200 nm (large enough to simplify the fabrication). Numerical simulations show that the present PBS has a good fabrication tolerance for the variation of the waveguide width (more than ± 60 nm) and a very broad band (~200 nm) for an extinction ratio of >10 dB.
Highlights
As a basic functional element, a polarization beam splitter (PBS) is very useful for many applications when polarization control is desirable [1]
An ultra-short PBS is realized by using the strong polarization dependence of the photonic crystal (PhC) structures (e.g., ~50μm [15], ~20μm [16]) or out-of-plane gratings (e.g., ~14μm [17,18])
We propose an ultra-short broadband PBS based on a bent directional couplers (DCs) structure
Summary
As a basic functional element, a polarization beam splitter (PBS) is very useful for many applications when polarization control is desirable [1]. “Compact silicon slot waveguide polarization splitter,” Opt. Eng. “A compact silicon-on-insulator polarization splitter,” IEEE Photon.
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