Subwavelength silicon photonic metamaterials for mode multiplexing and polarization control (Conference Presentation)

Subwavelength gratings (SWG) enable the synthesis of dispersion-engineered photonic metamaterials, leading to unprecedented performance in silicon photonic devices. In this work, we further explore the potential of this technology by presenting an ultra-broadband mode de/multiplexer (DE/MUX) and a polarization beamsplitter (PBS) with a novel approach for anisotropy engineering through tilted SWG structures. The proposed two-mode DE/MUX consists of a SWG-engineered multimode interference coupler (MMI), a 90\uba phase-shifter and a symmetric Y-junction. SWG structures are also included in fiber-to-chip couplers and in adiabatic transitions between Si-wire interconnect waveguides and the MMI. Simulated insertion losses of the proposed device are less than 0.18 dB in the wavelength range from 1.4 \u3bcm to 1.7 \u3bcm. These values further decrease down to 0.11 dB for the TE0 mode and 0.07 dB for the TE1 mode in the C-band wavelength range (1.53 \u2013 1.57 \u3bcm). Crosstalk of both modes is below -20.6 dB in the wavelength range from 1.4 \u3bcm to 1.7 \u3bcm and below -36 dB within the C-band. The proposed PBS consists of an MMI incorporating tilted sub-wavelength gratings. This novel anisotropy engineering technique provides independent control on the propagation constant of each polarization, enabling the implementation of shorter devices with improved performance. An extinction ratio over 20 dB and insertion losses below 1.5 dB in a 116-nm-wide bandwidth are demonstrated, for a MMI length under 100 \u3bcm.Peer reviewed: YesNRC publication: Ye