Side-polished fiber as a sensor for the determination of nematic liquid crystal orientation

The orientation change of nematic liquid crystal (NLC) has been the essential mechanism for various high sensitive sensors. In this paper, a side-polished fiber (SPF) is proposed to sense the orientation change of NLC. We successfully designed the liquid crystal cell embedded with a SPF that enabled us to mechanically rotate the orientation of NLC on the polished surface of the SPF. Our experimental results showed that the orientation change of NLC can indeed be sensed by monitoring the output optical power transmitted through the SPF. The increment of the transmitted optical power through the SPF was measured as large as 28.10 dB with the mechanical rotation from 0° to 90°. Within the angle range from 0° to 30°, the response was almost linear. The average response slope was about 0.359 dB/°, which indicated relatively high sensitivity. These experimental results indicate that SPF can be used to determine the orientation change of NLC. In particular, there exists a possibility that a SPF overlaid with NLC on its polished surface can potentially be made into a small transducer of a biosensor.