Methods and apparatus for vertical coupling from dielectric waveguides

摘要

A frequency-chirped nano-antenna provides efficient sub-wavelength vertical emission from a dielectric waveguide. In one example, this nano-antenna includes a set of plasmonic dipoles on the opposite side of a SiYV4 waveguide from a ground plane. The resulting structure, which is less than half a wavelength long, emits a broadband beam (e.g., >300 nm) that can be coupled into an optical fiber. In some embodiments, a diffractive optical element with unevenly shaped regions of high- and low-index dielectric material collimates the broadband beam for higher coupling efficiency. In some cases, a negative lens element between the nano-antenna and the diffractive optical element accelerates the emitted beam's divergence (and improves coupling efficiency), allowing for more compact packaging. Like the diffractive optical element, the negative lens element includes unevenly shaped regions of high- and low-index dielectric material that can be designed to compensate for aberrations in the beam emitted by the nano-antenna.

主权项

1. An apparatus comprising:
a waveguide to guide a first optical wave having a wavelength λ in a first direction; a vertical coupler, in optical communication with the waveguide and having a length in the first direction of about 10 nm to about 10 μm, to couple at least a portion of the first optical wave out of the waveguide so as to produce a second optical wave propagating in a second direction at an angle of about 80° to about 100° with respect to the first direction; a diffractive optical element, in optical communication with the vertical coupler and comprising at least one irregularly shaped region of first dielectric material, to collimate at least a portion of the second optical wave so as to produce a collimated wave.