Integrated Reconfigurable Unitary Optical Mode Converter Using MMI Couplers

Reconfigurable unitary optical mode converters that can convert multiple orthogonal spatial modes into different orthogonal modes without fundamental optical loss are important for mode-division-multiplexed (MDM) optical communication, imaging, and quantum computation. In this letter, we propose a novel integrated reconfigurable unitary optical mode converter, which consists of cascaded multimode interference couplers and phase shifter arrays. We numerically investigate its ability to realize arbitrary unitary mode conversion and demonstrate its applicability to mode unscrambling as well as mode switching in MDM transmission systems.