Theory of acousto-optic fiber Bragg grating coated with zinc oxide (ZnO)

An application of an optical fiber acousto-optic resonator using piezoelectric ZnO coating on the fiber Bragg grating surface was first introduced by Fox et al. (1997). The experiment demonstrated the shift of Bragg (or reflected) wavelength of the fiber Bragg grating of a few nanometres due to the acousto-optic effect while the piezoelectric was operating. So far the exact theory for this particular structure has not been described. This paper presents the modification theory for such a device structure. The theory agrees well with the experimental result previously demonstrated. It can be seen that the transmitted wavelengths in terms of a few nanometres can be fine-tuned by either adjusting the piezoelectric ZnO thickness or electrical power applied to the transducer.