Submicron-scale broadband polarization beam splitter using CMOS-compatible materials.

We propose a polarization beam splitter (PBS) with a footprint of only 600 × 790 nm operating at a wavelength of λ = 1550 nm, which is the smallest PBS ever demonstrated. This device uses CMOS-compatible materials, namely, silicon and silica. The present PBS comprises two Si waveguides with different geometrical aspect ratios adjoined side-by-side, which separates the transverse-electric (TE) and transverse-magnetic (TM) modes without relying on an additional coupling region. The designed PBS achieves a polarization extinction ratio of approximately 25 dB for both modes and insertion losses of approximately 0.87 and 1.09 dB for the TE and TM polarizations, respectively. Over a wide bandwidth of 150 nm (from λ = 1475-1625 nm), a high polarization extinction ratio (greater than 20 dB) and a low inversion loss (lower than 1.3 dB) can be obtained. The proposed PBS allows for geometrical errors of ±15 nm while maintaining a polarization extinction ratio of >20 dB and inversion losses of >1.1 and 1.3 dB for the TE and TM modes, respectively. With the submicron footprint, the reported PBS may be able to be used in high-density photonic integrated circuits and nanophotonic devices.