(초청강연논문) Design, Fabrication, and integration of Micro/Nano-scale Plasmonic Waveguide Devices for VLSI Photonic Circuit Application

초록

We present an overview of our work on the theory, design, fabrication, and integration of micro/nano-scale plasmonic waveguide devices for VLSI photonic integrated circuit applications. We first examine the characteristics and use of the slow light propagation and the fast light propagation on the design of various functions. We design both horizontally parallel directional couplers and vertically parallel directional couplers and compare their performances. For this, we designed and fabricated vertical directional couplers consisting of metal stripe waveguides embedded in polymer. The coupling length of the fabricated vertical directional coupler consisting of 20nm thin and 5um wide gold stripes was 260um. The extinction ratio was about 28dB and the separation distance of the two metallic waveguides was 4.2um. The fabricated vertical directional couplers were 9mm long in total length with the arm separation of 200um at the input/output section. The total insertion loss was measured as ~ 24dB and the additional loss was about ~3dB. We also designed and fabricated a novel metal-waveguide structure for sustaining long-range surface-plasmon-polaritons(LR-SPP), which is basically composed of two asymmetric metal layers: a very thin, finite-width metal strip on top of a metal slab with a dielectric gap in between. Mode cut-off of LR-SPPs excited on the asymmetric double-metal waveguides is characterized by investigating their dispersion relations and mode profiles. We confirm experimentally the existence of low-loss, well-confined LR-SPP modes by measuring far-field outputs emerging from an edge of the asymmetric double-metal waveguides. We then fabricated several types of SPP waveguide devices including straight line, S-bend, Y-branch, and couplers for the gold strip patterns (20 nm-thick, 5 um-wide). The Overall propagation loss of the asymmetric double-metal waveguides is comparable to that of single metal-strip waveguides. In addition, the mode sizes can be tuned by