  Multimode silicon photonics, leveraging mode-division multiplexing
technologies, offers significant potential to increase capacity of large-scale
multiprocessing systems for on-chip optical interconnects. These technologies
have implications not only for telecom and datacom applications, but also for
cutting-edge fields such as quantum and nonlinear photonics. Thus, the
development of compact, low-loss and low-crosstalk multimode devices, in
particular mode exchangers, is crucial for effective on-chip mode manipulation.
This work introduces a novel mode exchanger that exploits the properties of
subwavelength grating metamaterials and symmetric Y-junctions, achieving low
losses and crosstalk over a broad bandwidth and a compact size of only 6.5
{\mu}m {\times} 2.6 {\mu}m. The integration of SWG nanostructures in our design
enables precise control of mode exchange through different propagation
constants in the arms and metamaterial, and takes advantage of dispersion
engineering to broaden the operating bandwidth. Experimental characterization
demonstrates, to the best of our knowledge, the broadest operational bandwidth
covering from 1420 nm to 1620 nm, with measured losses as low as 0.5 dB and
extinction ratios higher than 10 dB. Enhanced performance is achieved within a
149 nm bandwidth (1471-1620 nm), showing measured losses below 0.4 dB and
extinction ratios greater than 18 dB.
