biostudies-literatureOh JNational Science Foundation929-937https://www.ebi.ac.uk/biostudies/studies/S-EPMC8931746biostudies-literatureUnknown9(3)Optical fiber communications rely on multiplexing techniques that encode information onto various degrees of freedom of light to increase the transmission capacity of a fiber. However, the rising demand for larger data capacity is driving the need for a multiplexer for the spatial dimension of light. We introduce a mode-division multiplexer and demultiplexer design based on a metasurface cavity. This device performs, on a single surface, mode conversion and coupling to fibers without any additional optics. Converted modes have high fidelity due to the repeated interaction of light with the metasurface's phase profile that was optimized using an inverse design technique known as adjoint analysis. We experimentally demonstrate a compact and highly integrated metasurface-based mode multiplexeACS photonicsAdjoint-optimized metasurfaces for compact mode-division multiplexing.PMC8931746ECCS-2025158Yang JDainese PCapasso FChen WTOh JLi KLi MJfalseAdjoint-optimized metasurfaces for compact mode-division multiplexing.Optical fiber communications rely on multiplexing techniques that encode information onto various degrees of freedom of light to increase the transmission capacity of a fiber. However, the rising demand for larger data capacity is driving the need for a multiplexer for the spatial dimension of light. We introduce a mode-division multiplexer and demultiplexer design based on a metasurface cavity. This device performs, on a single surface, mode conversion and coupling to fibers without any additional optics. Converted modes have high fidelity due to the repeated interaction of light with the metasurface's phase profile that was optimized using an inverse design technique known as adjoint analysis. We experimentally demonstrate a compact and highly integrated metasurface-based mode multiplexe2022-01-01T00:00:00Z2022 Mar2025-04-04T07:44:02.52Z2025-04-04T07:44:02.52ZS-EPMC89317463530840810.1021/acsphotonics.1c01744