Researchers have created a brand-new category of integrated photonic devices called “leaky-wave metasurfaces” that can transform the light that was once constrained in an optical waveguide into any optical pattern in free space. These devices’ simultaneous control of all four optical degrees of freedom—amplitude, phase, polarization ellipticity, and polarization orientation—is a global first. The devices can enhance optical displays, LIDAR (light detection and ranging), optical communications, and quantum optics since they are extremely thin, transparent, and compatible with photonic integrated circuits (PICs).
This work suggests new ways to develop hybrid systems that combine the best of both worlds — free-space optics for shaping the wavefront of light and integrated photonics for optical data processing, to address a variety of emerging applications, such as quantum optics, optogenetics, sensor networks, inter-chip communications, and holographic displays,
To regulate these two standing waves separately, they created a “leaky-wave metasurface” consisting of two sets of rectangular apertures offset by a subwavelength from one another. This process transforms each standing wave into a surface emission with independent amplitude and polarization. The two surface emission components form a single free-space wave with fully adjustable amplitude, phase, and polarization at every point along its wavefront.
At the telecom wavelength of 1.55 microns, the team experimentally proved that a variety of leaky-wave metasurfaces could transform a waveguide mode propagating along a waveguide with a cross-section on the order of one wavelength into free-space emission with a designer wavefront over an area roughly 300 times the wavelength.
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