High-Visibility, High-Strength, Rapid-Response, In-Fiber Optofluidic Sensor

Optofluidic sensors are promising tools in biological and chemical analysis. A challenge for optofluidic sensors in most practical applications is to have simultaneously high visibility, high mechanical strength, and rapid response for high-resolution, stable, and fast measurement. Here, we demonstrated an optofluidic sensor by splicing a hollow-core fiber (HCF) between a suspended-core fiber (SCF) and a single-mode fiber. By establishing the heat-conduction theoretical model of the SCF, an undeformed high-strength splicing technique was proposed. The undeformed splicing can eliminate the curvature of the end face of the core in the SCF, which is crucial to attain a high-visibility Fabry-Pérot cavity. Experimental results showed that the fringe visibility was up to 28 dB in air and 22 dB in water. Meanwhile, the measured mechanical strength of the splicing joint by the splicing technique reached to 30.02 kpsi, which is close to that of the HCF (37.84 kpsi) or SCF (39.45 kpsi). Moreover, the response time of this sensor was less than 1.5 s, and the refractive index sensitivity was 1153.74 nm/RIU. Therefore, the proposed sensor is a promising candidate in practical biological and chemical measurements.