Mode and Polarization Division Multiplexing Based on Chalcogenide-Glass-on-Thin-Film Lithium Niobate

We report integrated mode- and polarization-division multiplexing components on a high-index-contrast Ge₂₈Sb₁₂Se₆₀ (GeSbSe) chalcogenide-glass-loaded thin-film lithium niobate on insulator (LNOI) platform operating across the 1500-1570 nm wavelength range. By leveraging the direction-dependent birefringence of x-cut LNOI together with the strong optical confinement provided by the GeSbSe overlayer, we experimentally demonstrate a four-channel mode (de)multiplexer (MDM) and an asymmetric-directional-coupler-based polarization splitter-rotator (PSR). Over the full band, the MDM achieves insertion losses below 0.97, 0.31, 2.36, and 3.21 dB for the TE₀-TE₃ channels, with intermodal crosstalk better than -18.3, -19.2, -14.9, and -16.3 dB, respectively. The PSR exhibits insertion losses of 1.67 dB (TM₀ input) and 1.81 dB (TE₀ input), together with extinction ratios exceeding 20.7 and 31.6 dB. These results validate GeSbSe-on-LNOI as a scalable platform for broadband low-loss multidimensional multiplexing in high-capacity photonic integrated circuits.