Subwavelength Structure of the Evanescent Field of an Optical Bloch Wave

R. J. P. Engelen, D. Mori, T. Baba, L. Kuipers
2009 Physical Review Letters  
The periodic structure of a photonic crystal causes the propagating waves to be governed by Bloch's theorem: they are composed of multiple wave vectors or harmonics. We found, by measuring the field with phase-sensitive near-field microscopy, that the evanescent field of the composite Bloch wave decays nonexponentially as a function of height. Even the individual Bloch harmonics, having only a single wave vector along the propagation direction, do not necessarily decay single exponentially,
more » ... h has its origin in the spread of wave vectors required to confine the light to the waveguide. The complex decay leads to an evolution of the mode pattern as a function of the height above the structure.
doi:10.1103/physrevlett.102.023902 pmid:19257275 fatcat:hdwgdqgh6nddtf5unaxy2wgp2u