Single-slot hybrid microring resonator hydrogen sensor

Photonic integrated circuits fabricated on silicon-on-insulator platforms offer convenient foundations to implement highly sensitive, compact, robust, and low-cost technology in sensing applications. The potential of this technology in hydrogen gas sensing is discussed in this study. A single-slot hybrid microring-resonator- (MRR) based hydrogen gas sensor utilizing a coaxial palladium (Pd) microdisk is demonstrated. Detection is based on expansion of Pd upon hydrogen exposure toward the slot between the outer radius of the Pd microdisk and the inner radius of the MRR and the subsequent shift of the whispering gallery modes (WGMs) propagating in the MRR. Finite-difference time-domain simulations indicate a sensitivity as high as 11.038 nm/% hydrogen, provided that optimum geometrical design parameters are chosen. This sensitivity value is ∼23 times higher than other existing WGM-based hydrogen sensor demonstrations.