2x2 Ultra-Broadband Multimode Interference Coupler with Subwavelength Gratings Fabricated by Immersion Lithography

International audienceWe demonstrate an ultra-broadband 2x2 multimode interference (MMI) coupler leveraging subwavelength grating (SWG) nanostructures fabricated by immersion lithography. Excess loss of < 2 dB, power imbalance < 1.5 dB and phase error < 5° have been measured for a wavelength range of 1300 – 1680 nm. The small feature sizes, down to 75 nm, were well-defined using immersion lithography and optimized optical proximity correctio