具高介電係數對比之波導結構，因具備強模態侷限性、可高密度整合、可以成熟之半導體製程技術製作等特性，多年來已被廣泛地運用於積體光學元件中。然而，更進一步縮小傳統介質波導元件之尺寸卻礙於繞射極限之自然限制而無以為繼。因此以次波長結構傳導電磁能量已成為實現「奈米積體光路」與「整合奈米光子於奈米電子內」最基本之研究。在奈米光電中，以表面電漿極子(surface plamon polaritons)於奈米結構中傳播電磁能量之研究在過去十年間逐漸受到重視。現今一般公認表面電漿元件在實現奈米積體光路上極具潛力。然而，以目前先進之矽上絕緣層 (silicon-on-insulator)技術為基礎之介質波導其尺寸僅略大於電漿波導，且若製程得宜，其傳播損耗極小。若以元件尺寸與傳播損耗而言，現今已實驗驗證之表面電漿波導所具之優勢並不顯著。為了將光波自長距離光纖網路引入奈米積體光路中，結合高介電係數對比之介質波導與表面電漿結構之特性，或可在短時間內實現低傳播損耗、超高元件密度之奈米積體光路。於本研究計畫中，我們將發展全新之「金屬-多層介電質」波導並以其為基礎、實現對極化無選擇性之次波長90±波導轉折(waveguide bend)。此次波長90±波導轉折乃由金屬帶狀區域、二氧化矽間隙(gap) 與高介電係數之矽所組成。我們將研究此類波導之導波特性、發展「金屬-多層介電質」之90±轉折理論基礎以提供深刻之物理理解與系統化之設計規則、實驗驗證上述之構想、並預期以此電漿波導結構為基礎，發展其他適用於奈米積體光路中所需之各種被動元件。High-index contrast dielectric waveguides have been in widespread use for many years as they offer a strong mode confinement, dense integration, low propagation loss (if smooth sidewalls are attainable), and the ease of fabrication through mature semiconductor technologies. However, further downscaling waveguiding structures is hampered by the natural diffraction limit. Strong sub-wavelength field confinement thus becomes crucially important. Nanophotonics using surface plasmon polaritons (SPPs), also termed as plasmonics, has been attracting much renewed attention worldwide in the last decade and is now considered as a promising solution for the implementation of optical nanocircuitry. However, with the development of silicon-on-insulator technologies, plasmonic waveguides show marginal advantages over their dielectric-based counterparts in terms of the propagation loss and waveguide dimensions. In view of bringing light from long-haul optical networking into chip-scale photonic circuits by pushing the envelope of the current technologies, combining the advantages from both dielectric- and plasmonic-based structures, which may be complimentary to each other in nature, could pave the way toward high-performance, ultrahigh-density optical nanocircuitry in the future. In this research, we will be seeking a polarization-insensitive subwavelength 90± sharp waveguide bend in metal/multi-insulator configuration capable of offering high transmission efficiency within an ultrasmall footprint in optical telecommunication bands. It consists of a silica gap region sandwiched by a 300-nm-wide silver strip and a silicon waveguide core. Theoretical formalism on the transmission characteristics of the innovative structrure will be pursued for in-depth physical insights from which operation/design principles will be derived. Experimental demonstrations will also be conducted in which cross-polarizatoin measurement may be of great interest and importance. Based upon the metal/multi-insulator configuration, we will be working toward what would ultimately become a universal structure for the planar photonic ICs. 研究期間：10008 ~ 10107
