Waveguide-integrated spatial mode filters with PtSe2 nanoribbons

Low-dimensional material-based heterogeneous silicon photonics has attracted significant attention due to their applications in developing integrated optoelectronic devices from the telecommunication band to mid-infrared wavelengths. However, the study of waveguide components integrated with low-dimensional materials for mode-division multiplexing (MDM) applications mostly remains in its infancy. In this paper, we demonstrated waveguide-integrated spatial mode filters by integrating subtly designed ten-layer PtSe2 nanoribbons on an ultrathin silicon waveguide with a deep-subwavelength thickness to eliminate modal crosstalk. To be specific, the undesirable propagating mode can be filtered out due to its strong interaction with the PtSe2 nanoribbons on the silicon waveguide surface. Our results show that TE1-to-TE0 and TE2-to-TE0 modal extinction ratios of 12 dB and 14.5 dB were measured in 100 and 75-μm-long PtSe2-on-silicon waveguides at 2200-nm wavelengths. Our study paves the intriguing approach to developing waveguide-integrated spatial mode filters for on-chip MDM applications for optical interconnects and optical communications.