Compact and high conversion efficiency mode-sorting asymmetric Y junction using shortcuts to adiabaticity.

We propose a compact and high conversion efficiency asymmetric Y junction mode multiplexer/demultiplexer for applications in on-chip mode-division multiplexing. Traditionally, mode sorting is achieved by adiabatically separating the arms of a Y junction. We shorten the device length using invariant-based inverse engineering and achieve better conversion efficiency than the adiabatic device.