Characteristic analysis of HE_(11) mode in doubly cladding fiber with inner cladding made of negative-refractive-index material

A W-type weakly-conductive doubly cladding fiber with an inner cladding made of negative-refractive-index material and an external cladding and fiber core made of conventional material was investigated.An exact characteristic equation of oscillation mode was derived by using full vector method and Helmholtz equation without considering the material chromatic dispersion and medium loss.The influence of refractive index and thickness of inner cladding on HE11 mode of this left-handed fiber was discussed respectively.The chromatic dispersion curve and the curve of cut-off frequency versus inner layer thickness and inner layer refractive index were depicted and compared with those of the right-handed fiber HE11 mode.It was shown by analysis that doubly cladding fiber with an inner cladding made of negative-refractive-index material exhibited many different abnormal characteristics from conventional optical fiber,providing a theoretical basis for designing new optical devices.