Vertical-Fluid-Array-Induced Optical Microfiber Long-Period Grating (VIOLIN) Refractometer

We propose and experimentally demonstrate a highly flexible and applicable configuration, namely, the vertical-fluid-array induced optic microfiber long period grating (VIOLIN), for fully exploring the characteristics of liquids. The presence of flowing liquid in the periodically carved grooves of the designated substrate can activate a long-period grating resonance, as the microfiber is attached. Since the features of the resonance depend strongly on the refractive index of the fluid, the VIOLIN can be utilized as a refractometer with a high sensitivity of 2443 nm/RIU. Modeling and simulation are employed to investigate the mechanism of the sensor, which can be described as follows briefly: Liquid renders the resonance to light. Light deciphers the secret of liquid. Moreover, due to the highly elastic control of the fluidic array and the detachable configuration, multiple sensing and easy reconfiguration of the VIOLIN can be realized. The VIOLIN is expected to be highly suitable for microfiber-based chemo/biosensing applications.