Abstract

We designed and experimentally demonstrated an ultra-compact and ultra-broadband two-mode de-multiplexer based on a subwavelength grating (SWG) asymmetrical coupler (ADC) on a silicon-on-insulator (SOI) platform. The device consists of a cascaded strip waveguide tapered to a multimode segment and a SWG-based single-mode waveguide. Tapering the strip waveguide in multi-segments guarantees a high fabrication tolerance with a wider wavelength range of operation. The parameters of the periodic structure are chosen to meet the Bragg condition and phase-match the TE1 mode of the strip waveguide. These features produce a faster mode evolution with a shorter coupling length of only 8.5 μm and an entire mode division multiplexing (MDM) link (Mux and Demux) of only 55 μm. The MDM link operates over a wide wavelength range, covering the entire S-, C-, and L-bands. The insertion loss (IL) and crosstalk (CT) achieved at 1550 nm are better than 1 dB and −18 dB, respectively. The device also has low fabrication sensitivity to deviations in the waveguide's parameters. Additionally, the transmission performance of the link is demonstrated at 1550 nm wavelength using non-return-to-zero (NRZ) on-off keying (OOK) modulation, where clear eye diagrams are obtained at 64 Gbps.

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