We have designed, fabricated and characterized an integrated-nanophotonics polarization beamsplitter with a footprint of 2.4 × 2.4 μm2, which is the smallest polarization beamsplitter ever demonstrated. A nonlinear optimization algorithm was used to design the device for λ0 = 1,550 nm. The polarization beamsplitter and the input/output waveguides can be fabricated in a single lithography step. Here, we experimentally show an average transmission efficiency of greater than 70% (peak transmission efficiency of ∼80%) and an extinction ratio greater than 10 dB within a bandwidth of 32 nm. Simulation results indicate that our device is tolerant to fabrication errors of up to ±20 nm in the device thickness. We also designed, fabricated and characterized a mode-converting polarization beamsplitter, which not only separates the two polarization states but also connects one multimode input waveguide to two single-mode output waveguides.
At a glance
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