Optical fiber Fabry-Perot refractive-index sensor fabricated by femtosecond laser etching

The optical fiber Fabry-Perot(F-P) sensor is simulated and analyzed based on multi-beam interference principle.Then the micro F-P sensor is fabricated by 800 nm femtosecond laser mechanism on the single mode fiber.And the refractive index(RI) response is experimentally tested.The fabrication parameters can be tunable through controlling the computer.Under different fabricated parameters,the different reflection spectra of the F-P sensor can be formed.According to the theoretical analysis,the fringe contrast of the micro F-P sensor will decrease within the low refractive index region,and it will increase within the high refractive index regioin(low region:refractive index is less than 1.457;high region:refractive index is more than 1.457).The refractive index responses to a variety of different solutions are carried out.The results show that the sensitivities of the sensor interference fringe contrast to low and high refractive index solutions are 27.65 dB/RI and 3.50 dB/RI,respectively.And the experimental results of two refractive index regions both exhibit good linear response.This type of F-P sensor has advantages of high sensitivity,good reproducibility,anti-corrosion,and so on.It is easy to be fabricated by femtosecond etching technique.Thus,it has a great potential application in the refractive index sensing field of optical fiber sensors.