Measurement of the refractive index of a magnetic fluid by the retroreflection on the fiber-optic end face

A simple method based on the retroreflection on the fiber-optic end face is developed to measure the refractive index of a magnetic fluid in this letter. The measuring principle, accuracy, and sensitivity of this method are analyzed theoretically, and high precision and resolution can be achieved in principle. Experimental measurements are done to investigate the concentration and temperature dependent refractive index of the magnetic fluid. The linear dependence relation is obtained for both cases. The thermo-optical coefficient of the magnetic fluid is measured to be around −2.4×10−4°C−1.