Plasmonic Wavelength Demultiplexer with Mode Conversion Capabilities

Plasmonic Coupler and Multiplexer/Demultiplexer Based on Nano-Groove-Arrays

“…SPP wave propagating in the bus couples to the rectangular nano-groove-array evanescently and each groove emits light like a point source. Through a proper choice of the spacing of the individual grooves in the array, the emissions from the point sources can be constructively added to obtain a plane wave a few nanometers away from the nano-groove-array and which propagates in a chosen direction [26]. The emitted plane wave can be coupled into the coupling MIM waveguide in the desired direction, placed at a distance d, by etching a matching nano-groove-array on it.…”

“…The emitted plane wave can be coupled into the coupling MIM waveguide in the desired direction, placed at a distance d, by etching a matching nano-groove-array on it. It may be noted that the progressive variation in the groove depths in the waveguides is to ensure uniform emission and coupling of power [26]. Needless to say, by virtue of Helmholtz reciprocity theorem [27], the roles of the bus and coupling waveguides can be reversed in that SPP waves propagating in the lower waveguide can be coupled on to the waveguide at the top.…”

“…For SPP wave in the bus to propagate as a plane wave in free space in a desired direction, position of individual grooves in the array must be adjusted so that the field emitted by them add constructively in the desired direction. This spacing between the grooves s can be arrived at from the expression given in [26]. The expression in [26] can be further written in a more elegant form as discussed here.…”

“…This spacing between the grooves s can be arrived at from the expression given in [26]. The expression in [26] can be further written in a more elegant form as discussed here. The β and k 0 in [26] stand, respectively, for the magnitudes of propagation constant of SPP, also identified as k spp , and the free space propagation constant.…”

“…The expression in [26] can be further written in a more elegant form as discussed here. The β and k 0 in [26] stand, respectively, for the magnitudes of propagation constant of SPP, also identified as k spp , and the free space propagation constant. With sin(θ) expressed as -cos(θ + π/2) and using the definition of dot product between vectors, the equation in [26] becomes where as mentioned above, k spp is the SPP wave vector which can be calculated as explained in [1], n is a non-zero positive integer, k 0 is the free-space wave vector, and a kspp is a unit vector along the direction of propagation of the SPP wave in the bus.…”