Silicon photonic dual-gas sensor for H₂ and CO₂ detection

We report a silicon photonic dual-gas sensor based on a wavelength-multiplexed microring resonator array for simultaneous detection of H₂ and CO₂ gases. The sensor uses Pd as the sensing layer for H₂ gas and a novel functional material based on the Polyhexamethylene Biguanide (PHMB) polymer for CO₂ gas sensing. Gas sensing experiments showed that the PHMB-functionalized microring exhibited high sensitivity to CO₂ gas and excellent selectivity against H₂. However, the Pd-functionalized microring was found to exhibit sensitivity to both H₂ and CO₂ gases, rendering it ineffective for detecting H₂ in a gas mixture containing CO₂. We show that the dual-gas sensing scheme can allow for accurate measurement of H₂ concentration in the presence of CO₂ by accounting for the cross-sensitivity of Pd to the latter.