Tunability of Hi-Bi photonic crystal fiber integrated with selectively filled magnetic fluid and microfluidic manipulation.

Optical fiber microfluidics technology can implement the mutual tune of the light field and fluid in micro-nano scale. In this paper, one core of high-birefringence photonic crystal fiber (Hi-Bi PCF) is used as a microfluidic channel. The birefringence of Fe3O4 nanofluid is experimentally and theoretically investigated by selectively infiltrating the magnetic fluid into the core of the Hi-Bi PCF. The presence of magnetic fluid alters the birefringence of the original Hi-Bi PCF and can be modulated by the intensity of the external magnetic field. The optical field distribution is simulated, and the birefringence of the Hi-Bi PCF with selective filling is approximately 6.672×10-4. The experimental results show that the structure has a highly linear response to the external magnetic field from 0 Oe to 300 Oe, and the sensitivity is 16.8 pm/Oe with a high resolution of 1.19 Oe. Due to several advantages such as all-fiber compact structure, low transmission loss, and high linear response, this device can find various applications, including weak magnetic field measurement with high accuracy, optical fiber gyroscopes, and magneto-optic modulators. Particularly, it also has important significance to realize the all-fiber microfluidic chip laboratory.