Fiber Laser Incorporating an Intracavity Microchannel for Refractive Index and Temperature Sensing

In this letter, we present a standard linear cavity fiber laser incorporating a microchannel for refractive index (RI) and temperature sensing. The microchannel of ~6-mum width created by femtosecond laser aided chemical etching provides an access to the external liquid; therefore, the laser cavity loss changes with the liquids of different RIs. Thus, at a fixed pump power, the output laser power will vary with the change of RI in the microchannel. The results show that the proposed sensing system has a linear response to both the surrounding medium RI and temperature. The RI sensitivity of the laser system is on the order of 10^-5, while the temperature sensitivity is about 0.02degC. Both sensitivities could be further enhanced by employing a more sensitive photodetector and using higher pump power.