Light power sensor by using a photosensitive liquid crystal hybrid film on side polished fiber

A novel light power sensor is demonstrated by using side polished fiber (SPF) overlaid with a photoresponsive liquid crystal hybrid film. The mixture of 15%Azo, 20% ZLI811, and 65% nematic liquid crystal is overlaid on the flat area of SPF to form a mixture film of ~30m thickness. The film is irradiated by light of wavelength of 405nm through a phase mask with a period of ~528nm. An absorption peak in the transmission spectrum of 1520-1620nm of optical fiber is observed. Experiment shows that the wavelength of absorption peak will shift toward shorter wavelength as the irradiation power increases. The change of wavelength of absorption peak is approximately linear to the irradiation power while the irradiation powers are between 30-80mw in our initial experiments. The measured sensitivity of light power is about 1.154pm/uW for the demonstrated sensor.