Inkjet-Printed MoS₂ D‑Shaped Fiber for Resonance-Enhanced Optical Sensing

Two-dimensional (2D) materials have shown great potential for applications in environmental monitoring and sensing due to their unique physical and chemical properties. In particular, molybdenum disulfide (MoS₂) has emerged as a versatile 2D material platform for many optical and optoelectronic applications due to its high refractive index, large surface-to-volume ratio, and tunable bandgap. In this work, the integration of MoS₂ layers on a side-polished optical fiber with a D-shaped cross-section has been demonstrated using a low-cost and scalable inkjet printing technique. The MoS₂-integrated optical fibers are shown to offer strong wavelength-dependent light-matter interactions that can be controlled by the thickness of the 2D material, allowing for tuning of their operation across the entire telecom band. Using a printed device with a MoS₂ layer thickness of 30 nm, designed to exhibit a resonance-enhanced transmission dip at wavelengths of ∼1.50 μm, a refractive index sensor has been demonstrated using saline solutions. The experimental results have been verified via numerical simulations, confirming the sensitivity and flexibility offered by the 2D material structures. These results indicate that inkjet-printed MoS₂ optical fiber devices are suitable for the development of large-scale sensing networks.