We present a liquid refractive index (RI) sensor based on step-index multimode polymer optical fiber with a micro-hole drilled by the femtosecond laser. The experimental results show that in the RI operation range of 1.333-1.473, the sensor has a good linear loss (dB) response to the liquid RI in the micro-holes and a high sensitivity of 18 dB/RIU approximately. The experimental results are explained with the mode of the refraction loss caused by the hole-core interface and connection loss caused by the gap of the holes. The sensor has many advantages including high sensitivity and low cost.
© 2014 Chinese Optics LettersPDF Article