研究期間：10108~10207;Nanophotonics using surface plasmon polaritons (SPPs), also termed plasmonics, has been attracting much renewed attention worldwide in the last decade for its potential in realizing optical nanocircuitry and in eventually bringing light into nanoelectronics, all using mature semiconductor manufacturing technologies. As having long been used in micro-photonics, coupling mechanism shall continue to prevail in photonic integrated circuits at nanoscale. The strong coupling effect that is often negligibly small in the past would become appreciable as the device separation distance decreases to deep sub-microns or few tens of nanometers. Furthermore, with the introduction of metal to constitute the plasmonic mode in optical nanocircuitry, the material loss can never be assumed null anymore. Understanding the strong coupling mechanism in an inherently-lossy system at nanoscale, therefore, becomes critically fundamental yet paramount. In general, conventional coupled-mode theory, regardless of being orthogonal or non-orthogonal, is derived for the lossless system. Those touching the lossy optical system seem to be very few or not sufficiently rigorous. In this research, complex nonorthogonal coupled-mode theory for lossy integrated photonics based on SPPs will be developed. In particular, strong-coupling and weak-coupling cases will be examined in a novel directional-coupler-based plasmonic polarization splitter that serves as a representative case. Analytical formulations for power transfer will be pursued and comparisons between theoretical predictions and numerical results will be made for both two-dimensional (2-D) and 3-D cases. The new theoretical formulation targeted would be of great importance in applications in nanophotonics/plasmonics that are lossy in nature (e.g. ring resonators, metal gratings, etc.). Experimental demonstrations will also be conducted in which polarization-related measurements are of great interest and importance.
