Mode-insensitive and mode-selective optical switch based on asymmetric Y-junctions and MMI couplers

Driven by the large volume demands of data in transmission systems,the number of spatial modes supported by mode-division multiplexing (MDM) systems is being increased to take full advantage of the parallelism of the signals in different spatial modes.As a key element for photonic integrated circuits,the multimode waveguide optical switch (MWOS) is playing an important role for data exchange and signal switching.However,the function of the traditional MWOS is simple,which could only implement the mode-insensitive or mode-selective switching function;it is also difficult to scale to accommodate more spatial modes because of the limitation of the device structure.Therefore,it is still challenging to realize a multifunctional and scalable MWOS that could support multiple modes with low power consumption and high flexibility.Here,we propose and experimentally demonstrate a multifunctional MWOS based on asymmetric Y-junctions and multimode interference(MMI) couplers fabricated on a polymer waveguide platform.Both mode-insensitive and mode-selective switching functions can be achieved via selectively heating different electrode heaters.The fabricated device with the total length of～0.8 cm shows an insertion loss of less than 12.1 d B,and an extinction ratio of larger than 8.4 dB with a power consumption of～32 mW for both mode-insensitive and mode-selective switching functions,at1550 nm wavelength.The proposed MWOS can also be scaled to accommodate more spatial modes flexibly and easily,which can serve as an important building block for MDM systems.