Optical Transport Phenomena in Coupled Spherical Cavities

The efficiency of optical transport is studied in one-dimensional (ID) chains and in 3D lattices of coupled microspheres with ~1-3% size disorder. To couple light into such structures we used sources of light formed by dye-doped fluorescent microspheres. Using techniques of spatially resolved scattering spectroscopy we observed large propagation losses (~ 3 dB per sphere) along the chain at the frequencies of whispering gallery modes (WGMs) in the source sphere. Away from the resonance with WGMs we observed much smaller losses (< 1 dB per sphere) due to formation of nanojet-induced modes. The propagation of light in 3D lattices of disordered coupled cavities with WGM resonances is interpreted in terms of percolation theory. In transmission spectra of such 3D structures we observed spectral signatures of strong coupling between multiple spheres with nearly resonant WGMs. The results indicate that the transmission properties can be significantly improved in 3D structures formed by more uniform spheres due to achieving an optical percolation threshold for WGM transport.