A novel microstrip coupled-line directional coupler is proposed in this paper. It is based on the introduction of a complementary split ring resonator and dumbbell-like defected ground structure on the coupled lines to strongly enhance the designed backward coupling. The designed frequency band is from 1.2 to 1.5GHz. The coupler is fabricated and tested. The insertion loss is less than 3.5 dB. ...

A polarization-independent optical directional coupler based on slot waveguides is proposed and analyzed by using rigorous full-vectorial analysis methods based on a finite-element scheme. Properly choosing materials and structural parameters makes the coupling length for quasi-TE modes become equal to that for quasi-TM modes. Tolerances to operating wavelength and structural parameters are als...

Directional mode coupling in an asymmetric holey fiber coupler is demonstrated both numerically and experimentally for the first time. The holey fiber mode couplers have interesting spectral characteristics and are also found to exhibit increased dimensional tolerances. Following a design based on numerical investigations, a dual-core polymer holey fiber coupler for LP(01) and LP(11) mode multi...

We analyze hybrid plasmonic waveguides with metallic layers on two sides. Confinement of closely stacked metal induces large difference of effective indices of vertical even and odd modes. This phenomenon can be utilized as ultracompact vertical directional coupler. Simulation shows directional coupling can be achieved in less than 1 μm.

A novel, wideband, symmetrical, printed directional coupler is described, which has tight coupling and high directivity. The coupler consists of four interconnected strips printed in two layers. The dimensions of the strips are optimized to minimize the dispersion of propagating modes. Design data are provided for some typical practical cases. The theoretical results are verified experimentally...

Resonator-based optical circulators are fundamentally bandwidth-limited by their quality factors. We propose a new type of circulator based on directional coupling between one-way photonic chiral edge states and conventional two-way waveguides. The operational bandwidth of such circulators is tied to the bandwidth of the directional waveguide coupler and has the potential for simultaneous broad...