Observation of light propagation across a 90° corner in chains of microspheres on a patterned substrate

To demonstrate light-path manipulation in arbitrary shapes we fabricated coupled-resonator optical waveguides (CROWs) having a 90°-corner structure on a lithographically patterned substrate. The spectra of propagation light within the CROWs were directly measured by guide-collection-mode near-field scanning optical microscopy. The spectra revealed that the propagation light through the CROWs has a larger transverse-magnetic polarization mode than a transverse-electric (TE) one. The most plausible cause of the lower intensity in the TE mode is that light leaks out to the Si substrate.