Acousto-optic-induced cladding-mode reflection in a blazed-superstructure fiber grating

The coupling phenomenon between the cladding mode and the core mode in a blazed-superstructure fiber grating is experimentally demonstrated in this letter by applying both transverse and longitudinal acoustic waves. This is based on the difference between the cladding-mode wave vector and the core-mode wave vector, which is equivalent to the acoustic wave vector. By this means, a reflectivity-tunable multiwavelength switchable comb filter would be developed for the applications in fiber optics.