Efficient free-space optical coupler into dielectric waveguide with great field enhancement

We propose an efficient optical coupler to launch free-space signals into a dielectric dielectric waveguide via plasmonic structures with great field enhancement. A plasmonic concentrator composed of a subwavelength slit surround by periodic grooves is used to access and collect free-space light. The transmitted light is then unidirectional directed into a dielectric waveguide with a plasmonic Bragg reflector and a directional coupler. The free-space optical coupler is useful as it combines the plasmonic structure for optical signal access in subwavelength scale with the ultra-low loss dielectric waveguide for long-distance signal transmission and processing making use of nonlinearity.