Highly sensitive fiber-optic sensor based on ZnO/PVA composite and the Vernier effect for UV and blue light detection

High-precision detection of ultraviolet and blue light intensity remains a major challenge in monitoring fields such as industrial, medical, and laboratory applications. This paper proposes a strategy to enhance the sensing performance of FPI cavity using a ZnO/PVA composite material. Leveraging the photo-generated carrier effect of ZnO, the refractive index within the cavity is directly modulated, yielding high-sensitivity wavelength modulation for both UV and blue light. Experimental results show that the FPI 1 cavity with ZnO/PVA composite material achieves a UV sensitivity of 0.273 nm/(mW·cm −2 ) and a blue sensitivity of 0.267 nm/(mW·cm −2 ). Furthermore, a dual-cavity structure (S 1 ) based on the Vernier effect, formed by connecting FPI 1 and FPI 2 in parallel, demonstrates significantly enhanced sensitivities of −2.140 nm/(mW·cm −2 ) for UV light and −2.392 nm/(mW·cm −2 ) for blue light. In addition, the proposed sensing element features facile fabrication, excellent stability, and a relatively simple fiber-optic configuration. This work provides a high-performance fiber-optic approach for UV and blue-light intensity detection, with a low-cost and convenient sensing-element fabrication process.