Micro demultiplexer fabricated by self-assembly of microspheres on a patterned substrate

To demonstrate light-path manipulation in arbitrary shapes, we fabricated coupled-resonator optical waveguides (CROWs) having a 90deg-corner structure on a lithographically patterned substrate using a simple self-organization process. The spectra of propagation light within the CROWs were directly measured by guide-collection-mode near-field scanning optical microscopy (NSOM) techniques. The spectra revealed that the propagation light through the CROWs has a larger relative intensity of transverse-magnetic (TM) polarization mode than that of transverse-electric (TE) one, whereas Mie theory predicts the intensities of both to be nearly equal. The most plausible cause of the lower intensity in the TE modes is that light leaks out to, and is absorbed by, the patterned Si substrate, because the observable TE light in our setup goes around the microspheres in the vertical plane.