Ultra‐Sharp Multimode Waveguide Bends with Subwavelength Gratings

Abstract

AbstractMode‐division multiplexing (MDM) is attractive to enhance the link capacity of optical interconnects by using multiple mode‐channels in multimode bus waveguides. As sharp waveguide bends are very important for realizing dense photonic integrated circuits, here ultra‐sharp multimode waveguide bends for MDM systems are proposed and demonstrated by using subwavelength grating waveguide structures on silicon. An ultra‐sharp S‐bend with a radius of 10 µm is realized for the first time to enable a low‐loss and low‐crosstalk MDM optical interconnect with three mode‐channels. For this proposed ultra‐sharp subwavelength grating multimode waveguide bend (SMWB) with a 90° bending angle, the theoretical excess losses for the TE0, TE1, and TE2 modes are 0.1–0.3 dB, 0.18–0.22 dB, and 0.3–0.5 dB, respectively, in a wavelength band of 1500–1600 nm. Meanwhile, inter‐mode crosstalks are very low (less than −30 dB) for all mode‐channels. For the fabricated 90°‐SMWB, the excess losses for the TE0, TE1, and TE2 modes are 0.1–0.3 dB, 0.2–0.4 dB, and 0.3–0.7 dB while the inter‐mode crosstalk is approximately −22 dB in a wavelength band of 1520–1600 nm. The proposed SMWB is also extended for more than three mode‐channels.