Measurements of refractive index sensitivity using long-period grating refractometer

摘要

We report the development and demonstration of a long-period grating refractometer. The principle of operation is based on the using of a long-period grating that is structurally induced by a CO_(2) laser, and where the resonance wavelengths are shifted as the refractive index of medium surrounding the cladding of the long-period grating. The different concentrations for three types of solutions (ethylene glycol, salt, and sugar) were experimentally measured, and results show that, as a refractometer, this fiber-based device not only can differentiate chemicals based on their refractive index, but it can also become a concentration indicator of a particular chemical solution, and applied in the oil and petroleum industry.