Extremely Local Electric Field Enhancement and Light Confinement in Dielectric Waveguide

Extremely local electric field enhancement and light confinement are demonstrated in dielectric waveguides with corner and gap geometry. Classical electromagnetic theory predicts that the field enhancement and confinement abilities are inversely proportional to radius of rounded corner (r) and gap (g), and shows a singularity for infinitesimal r and g. For practical parameters with r = g = 10 nm, the mode area of opposing apex-to-apex fan-shaped waveguides can be as small as 4 × 10^-3 A₀ (A₀ = λ²/4), far beyond the diffraction limit. The lossless dielectric corner and gap structures offer an alternative method to enhance light-matter interactions without the use of metal nanostructures, and can find applications in quantum electrodynamics, sensors, and nanoparticle trapping.