Slot antenna efficiently couples light from optical circuits into the far-field

A “leaky wave” nonresonant plasmonic slot antenna designed by three researchers at the University of Toronto (Toronto, ON, Canada) is predicted to be a very efficient way to couple light from nanoscale optical circuits to the far-field. One of its interesting properties is its broadband nature: over a wavelength band ranging from 1200 to 2000 nm, its far-field radiation angle of 32º stays virtually constant. The optical antenna is extremely compact, radiating 90% of the input power for a length of half the light’s center wavelength (1550 nm in the model) and 99.9% of the input power for a length of 1.5 times the light’s center wavelength.

The device should be straightforward to fabricate, consisting of a single subwavelength slot in a 46-nm-thick layer of aluminum on silicon. Varying the thickness of the aluminum layer by 10% from nominal does not significantly alter the radiation pattern, which indicates that the design is tolerant of fabrication errors. The concept can be extended to an array of side-by side slots, which would radiate in synchrony and narrow the output shape from a cone to a pencil beam. The device could be useful for optical interconnects and in spectroscopy.

Contact George Eleftheriades at [email protected].