Compact Z-add-drop wavelength filters for long-range surface plasmon polaritons

We design, fabricate and investigate compact Z-add-drop (ZAD) filters for long-range surface plasmon polaritons (LR-SPPs) at telecom wavelengths. The ZAD filter for LR-SPPs consists of two ridge gratings formed by periodic gold thickness modulation at the intersections of three zigzag-crossed gold stripes embedded in polymer. We investigate influence of the grating length and crossing angle on the filter characteristics and demonstrate a 10 masculine- ZAD filter based on 80-microm-long gratings that exhibit a 15-dB dip (centered at ~ 1.55 microm) in transmission of the direct arm along with the corresponding ~ 13-nm-wide transmission peak in the drop arm.