Slot Waveguide Ring-Assisted Mach–Zehnder Interferometer for Sensing Applications

We experimentally demonstrate a ring-assisted Mach-Zehnder interferometer (RAMZI) design with slot waveguides for bulk index sensing using sucrose solution. Devices were implemented with both directional couplers (DCs) and multimode interferometer couplers (MMIs). The RAMZI designs with DCs were found to have a sensitivity of 203.3 ± 15.3 nm/RIU, while 177.2 ± 12.0 nm/ RIU was demonstrated with MMIs-coupled RAMZI. The free spectral ranges (FSRs) of DCs and MMIs-coupled RAMZI were measured to be 24.3 and 34.3 nm, respectively. The FSRs demonstrated can be as wide as 7.9 times larger than the equivalent microring resonator.