When several hollow photonic crystal fibers (HPCFs) are placed in proximity to each other, radiation-induced interfiber coupling between their core guided modes is observed. Under certain conditions coupling between the core modes of two touching collinear fibers can have a resonant increase via excitation of a low-quality intermirror cavity resonant state. Such coupling, however, decreases dramatically within the first micrometer of intermirror separation. Moreover, when fibers are touching, in the frequency domain a large number of accidental degeneracies with fiber surface and mirror states complicate the design of a stable 2×2 coupler. To alleviate these problems we consider coupling among three hollow Bragg fibers. When placed in the vertices of an isosceles triangle, even for a finite separation between fibers, triangular interfiber cavity forms a high-quality resonator that can be tuned via additional structural elements to a particular frequency of interest. Interfiber surface states are suppressed by keeping the fiber separation finite, thus allowing stable coupling conditions in a 3×3 HPCF coupler configuration.
© 2005 Optical Society of America
(060.1810) Fiber optics and optical communications : Buffers, couplers, routers, switches, and multiplexers
(060.2340) Fiber optics and optical communications : Fiber optics components
(230.5750) Optical devices : Resonators
Fiber Optics and Optical Communications
M. Skorobogatiy, "Design principles of multifiber resonant directional couplers with hollow Bragg fibers: example of a 3×3 coupler," Opt. Lett. 30, 2849-2851 (2005)