Dependence of leaky mode coupling on loss in photonic crystal fiber with hybrid cladding

Abstract

It is possible for core leaky mode to couple with cladding defect leaky mode when the cladding defect is close to fiber core. Dispersion properties and propagation loss of core mode will be affected in some extent once the coupling occurs. But a complete coupling between two leaky modes not always happens even the phase matching condition is satisfied. Leaky mode coupling in photonic crystal fiber with a hybrid cladding which includes low-index and high-index inclusions at the same time is numerically investigated based on a full vector finite element method. It is found that not only phase matching but also loss matching plays an important role in leaky mode coupling. The originally intersecting dispersion curves for the two leaky modes will split and become another two new curves due to the anti-crossing effect when both the real and imaginary parts of their mode effective refractive indices are equal. There is not splitting but some perturbation in dispersion curves for the two phase matching leaky modes when their losses are not equal. A theoretic explanation is also given to these phenomena.

Polarization characteristics of photonic crystal fibers selectively filled with metal wires into cladding air holes

“…2(a). This phenomenon can be explained by the leaky mode coupling [13]. The dispersion curve of a core mode splits into another two modes where the complete coupling happens, such as the anti-crossing region where the coupling to the 2 nd -order SPP mode occurs in Fig.…”

Bending performance of large mode area multi-trench fibers

“…It is well known that for a complete resonant coupling to take place between two leaky modes, there are two basic conditions to satisfy. First one is the phase matching and second one is the loss matching of two leaky modes under coupling [16].…”

Extending single mode performance of all-solid large-mode-area single trench fiber

“…4(e)) including both core and resonant ring modes [28]. On the other hand, in bent case HOMs of STF have high loss compared to low NA-SIF case thanks to the bend induced resonant coupling between core and resonant ring modes [29][30]. It is well known that for a complete resonant coupling to take place between two leaky modes, there are two basic conditions to satisfy.…”

“…It is well known that for a complete resonant coupling to take place between two leaky modes, there are two basic conditions to satisfy. First one is the phase matching and second one is the loss matching of two leaky modes under coupling [30]. We need to keep in mind that the modes of both core and resonant ring are leaky in bend condition and here our propose is to have high losses for HOMs of core irrespective of focusing on complete resonant coupling between core and resonant ring modes.…”