Reconfigurable Guided‐Mode Conversion Using Cladding Medium Switching Strategy in Subwavelength Grating Waveguide

Abstract

AbstractIn a waveguide‐based coupled‐mode system, various mode conversions are achieved by designing mode evolution procedures. However, the differences of refractive indices among modes exceed the capability of conventional tuning mechanism, so most reported mode manipulation devices can only realize fixed mode conversions. This paper introduces the cladding medium switching strategy to the subwavelength grating waveguide‐based coupled‐mode system, and proposes a reconfigurable mode converter on silicon nitride platform. This work systematically analyzes the phase matching conditions on a coupled‐mode system. Results show that for both whole and partial upper‐cladding switchable, it is possible to achieve reconfigurable mode conversions. For whole cladding switchable case, this work demonstrates a double‐state mode converter, which converts the input mode to TE2 and TE1 modes under cladding refractive indices of 1 and 1.7. This work expands it to triple‐state mode conversion with window‐style cladding, which converts the input to TE2, TE1, and TE0 modes under cladding of 1, 1.54, and 1.7. The optical bandwidths are relatively large, and the conversion efficiencies exceed 56% for all cases. The mechanism provides a non‐volatile and energy‐efficient way for tunable mode conversions, which is promising for applications in optical networks, communications, and sensors, etc.