ABSTRACT
We theoretically demonstrate spontaneous PT-symmetry breaking behavior of surface-plasmon polaritons (SPP) in coupled double-slab (DS) waveguides. By virtue of a flat-top field at critical wavelength, the imaginary index of a DS-SPP mode can be controlled via changing the core thickness, while the real index is kept constant. Therefore, a waveguide coupler that consists of a pair of DS-SPP waveguides with different core thicknesses can represent a passive PT-symmetric system, which always maintains symmetry under a real potential. This set-up also represents a good opportunity to investigate the underlying physics of PT-symmetry breaking in non-Hermitian Hamiltonian systems.
ABSTRACT
We suggest a compact and efficient duplexer using the multimode interference (MMI) effect and the extraneous self-imaging phenomenon for gigabit-capable passive optical network and gigabit Ethernet passive optical network applications. To experimentally evaluate the suggested duplexer, silica-based MMI couplers were tested using light sources with wavelengths of 1310 and 1490 nm. From the experimental results, this device showed relative output powers of -0.3 and -0.7 dBm for the light sources with 1490 and 1310 nm wavelengths, respectively. The return power was measured to be less than -40 dBm.
ABSTRACT
We discuss a self-imaging phenomenon in a multimode interference (MMI) coupler. From experiment, different self-images, which are undefined in MMI theory, are observed. These undefined self-images are named "extraneous self-images" (Ex_SIs) for convenience. To estimate the applicability of the Ex_SIs, the characteristics of both the single self-image (0 dB self-image, 0 dB SI), which is defined in MMI theory, and the Ex_SI are compared and analyzed through simulation and experiment. The results show that the Ex_SI has an imaging period that is the same as the 0 dB SI and that the excess loss and the extinction ratio of the Ex_SI improve more than that of the 0 dB SI as the imaging period increases.
