Two-pair multilayer Bloch surface wave platform in the near- and mid-infrared regions

A Bloch surface wave (BSW) platform opens up new possibilities in the design of sensors and components for photonic circuits owing to its superior properties such as low propagation losses that enable long optical communication lengths and large surface sensing areas. However, most of the reported BSW platforms require a large number of alternating layers to realize the coupling of the surface wave mode. Additionally, although BSW modes have been investigated in the visible region and the near-infrared (NIR) region, only limited reports are available in the important mid-infrared (MIR) region. In this study, we demonstrated a BSW platform consisting of only two Ge/SiO2 pairs and realizing well-coupled BSW in a wide spectral range from the NIR to the MIR. Exploiting the large refractive index difference between Ge and SiO2, the proposed BSW multilayer structure is designed to possess only two pairs of layers with a smaller total thickness than any of the reported BSW platforms. The reported MIR BSW mode shows potential for determination of trace elements and molecule species attached on the surface of the proposed BSW structure. Published under license by AIP Publishing.