Abstract
A new way to make broadband polarizers on silicon-on-insulator (SOI) waveguides is proposed, analyzed and characterized. The characteristics of the eigenmodes in a shallowly-etched SOI ridge optical waveguide are analyzed by using a full-vectorial finite-different method (FV-FDM) mode solver. The theoretical calculation shows that the loss of TE fundamental mode could be made very low while at the same time the TM fundamental mode has very large leakage loss, which is strongly dependent on the trench width. The leakage loss of the TM fundamental mode changes quasi-periodically as the trench width w(tr) varies. The formula of the period ∆w(tr) is given. By utilizing the huge polarization dependent loss of this kind of waveguide, a compact and simple optical polarizer based on a straight waveguide was demonstrated. The polarizer is fabricated on a 700 nm-thick SOI wafer and then characterized by using a free-space optical system. The measured extinction ratio is as high as 25 dB over a 100 nm wavelength range for a 1 mm-long polarizer.
Highlights
Polarization multiplexing and demultiplexing are important in photonic integrated circuits (PICs) for fiber optic communication, optical sensing, and optical signal processing
The characteristics of the eigenmodes in a shallowly-etched SOI ridge optical waveguide are analyzed by using a full-vectorial finite-different method (FV-FDM) mode solver
The theoretical calculation shows that the loss of TE fundamental mode could be made very low while at the same time the TM fundamental mode has very large leakage loss, which is strongly dependent on the trench width
Summary
Polarization multiplexing and demultiplexing are important in photonic integrated circuits (PICs) for fiber optic communication, optical sensing, and optical signal processing. In Ref [1,2,3], an antiresonant reflecting optical waveguide (ARROW) structure is used for realizing a polarizer. The theoretical calculation shows that it possible to realize a high extinction ratio of 30dB and a low loss of 0.1dB by using a rather short length of 50μm. This type of polarizer is sensitive to the dimensional variations and the wavelength shift. By optimally designing the shallowly-etched straight optical waveguide, the polarization dependent loss is maximized and a compact polarizer with high extinction ratio is achieved
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