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

ABSTRACT We report integrated mode‐ and polarization‐division multiplexing components on a high‐index‐contrast Ge 28 Sb 12 Se 60 (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 TE 0 –TE 3 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 (TM 0 input) and 1.81 dB (TE 0 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.