We propose a new power-splitting scheme in two-dimensional photonic crystals that can be applicable to photonic integrated circuits. The proposed power-splitting mechanism is analogous to that of conventional three-waveguide directional couplers, utilizing coupling between guided modes supported by line-defect waveguides. Through the analysis of dispersion curve and field patterns of modes, the position in propagation direction, where an input field is split into a two-folded image, is determined by simple mode analysis. Based on the calculated position, a photonic crystal power-splitter is designed and verified by finite-difference timedomain computation.

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We show that the self-imaging principle still holds true in multimode photonic crystal (PhC) line-defect waveguides just as it does in conventional multi-mode waveguides. To observe the images reproduced by this self-imaging phenomenon, the finite-difference time-domain computation is performed on a multi-mode PhC line-defect waveguide that supports five guided modes. From the computed result, the reproduced images are identified and their positions along the propagation axis are theoretically described by self-imaging conditions which are derived from guided mode propagation analysis. We report a good agreement between the computational simulation and the theoretical description. As a possible application of our work, a photonic crystal 1-to-2 wavelength demultiplexer is designed and its performance is numerically verified. This approach can be extended to novel designs of PhC devices.

The enhanced electroluminescence of GaN-based light-emitting diodes (LEDs) with noble metallic nanoparticles (MNPs) is demonstrated. The sample with well-designed Ag MNPs has shown the best performance enhancement of 126% in electroluminescent intensity compared with a conventional LED sample, even though the MNPs are placed at least 200 nm away from the quantum-well active layer. The MNPs provide enhanced photon scattering and coupling between localized surface plasmon resonance (LSPR) modes and photon modes internally trapped in a device. To investigate this effect, the peculiarities of the LSPR and the corresponding structural properties of the MNPs are discussed through the effective medium approach.

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