A theoretical evaluation of the absorption coefficient of the optical waveguide chemical or biological sensors by group index method

In this paper, an approach which we refer to as group index method was proposed to evaluate the absorption coefficient of the optical waveguide chemical or biological sensors. In this method, the absorption coefficient is regarded as mainly determined by the group index and the power fraction in the region of an absorptive medium. The absorption coefficient of the normal plane wave absorption; of the evanescent wave absorption which includes the type of open clad, buffered clad and sensing layer; and of the guided wave absorption for TE modes were investigated by this method. Some suggestions for optimizing the structure of the optical waveguide sensors were given.