A　waveguide　fabricated　on　top　of　a　bottom-waveguided　gold-nanowire　grating　device　excites　additional　resonance　modes　through　interaction　between　the　two　waveguides,　which　overlaps　the　＂intrinsic＂　resonance　mode　of　the　bottom　waveguide.　Thus,　the　TE　polarized　(parallel　to　the　gold　nanowires)　waveguide　mode　and　TM　polarized　(perpendicular　to　the　nanowires)　coupled　mode　between　the　waveguide　mode　and　the　particle　plasmon　resonance　of　the　gold　nanowires　are　enhanced　significantly　in　a　tunable　spectral　band.　The　top　waveguide　also　extends　considerably　the　spectral　tuning　range　of　this　optical　filter　device.　(C)　2008　American　Institute　of　Physics.