{"id":7968,"date":"2023-07-17T14:53:59","date_gmt":"2023-07-17T06:53:59","guid":{"rendered":"https:\/\/www.huashu-tech.com\/?p=7968"},"modified":"2023-07-17T14:54:05","modified_gmt":"2023-07-17T06:54:05","slug":"leaky-wave-metasurfaces-a-perfect-interface-between-free-space-and-integrated-optical-systems","status":"publish","type":"post","link":"https:\/\/www.huashu-tech.com\/fr\/leaky-wave-metasurfaces-a-perfect-interface-between-free-space-and-integrated-optical-systems\/","title":{"rendered":"M\u00e9tasurfaces \u00e0 ondes de fuite\u00a0: une interface parfaite entre les syst\u00e8mes optiques en espace libre et int\u00e9gr\u00e9s"},"content":{"rendered":"

Researchers at Columbia Engineering have developed a new class of integrated photonic devices\u2014”leaky-wave metasurfaces”\u2014that can convert light initially confined in an optical waveguide to an arbitrary optical pattern in free space. These devices are the first to demonstrate simultaneous control of all four optical degrees of freedom, namely, amplitude, phase, polarization ellipticity, and polarization orientation\u2014a world record.<\/p>\n

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Because the devices are so thin, transparent, and compatible with\u00a0circuits int\u00e9gr\u00e9s photoniques<\/a>\u00a0(PICs), they can be used to improve optical displays, LIDAR (Light Detection and Ranging), optical communications, and quantum optics.<\/p>\n

“We are excited to find an elegant solution for interfacing free-space optics and integrated photonics\u2014these two platforms have traditionally been studied by investigators from different subfields of optics and have led to commercial products addressing completely different needs,” said Nanfang Yu, associate professor of applied physics and applied mathematics who is a leader in research on nanophotonic devices.<\/p>\n

“Our work points to new ways to create hybrid systems that utilize the best of both worlds\u2014free-space optics for shaping the wavefront of light and integrated photonics for optical data processing\u2014to address many emerging applications such as quantum optics, optogenetics, sensor networks, inter-chip communications, and holographic displays.”<\/p>\n

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\"Leaky-wave
Left: Photo of two leaky-wave metasurfaces for generating Kagome lattices. Right: SEM image of a portion of a leaky-wave metasurface, which is composed of nano-apertures etched into a polymer layer on top of a silicon nitride thin film. Credit: Heqing Huang, Adam Overvig, and Nanfang Yu\/Columbia Engineering<\/figcaption><\/figure>\n<\/div>\n<\/div>\n

Bridging free-space optics and integrated photonics<\/h2>\n

The key challenge of interfacing PICs and free-space optics is to transform a simple waveguide mode confined within a waveguide\u2014a thin ridge defined on a chip\u2014into a broad free-space wave with a complex wavefront, and vice versa. Yu’s team tackled this challenge by building on their invention last fall of “nonlocal metasurfaces” and extended the devices’ functionality from controlling free-space light waves to controlling guided waves.<\/p>\n

Specifically, they expanded the input waveguide mode by using a waveguide taper into a slab waveguide mode\u2014a sheet of light propagating along the chip. “We realized that the slab waveguide mode can be decomposed into two orthogonal standing waves\u2014waves reminiscent of those produced by plucking a string,” said Heqing Huang, a Ph.D. student in Yu’s lab and co-first author of the study, published today in\u00a0Nature Nanotechnologie<\/i>.<\/p>\n

“Therefore, we designed a ‘leaky-wave metasurface’ composed of two sets of rectangular apertures that have a subwavelength offset from each other to independently control these two standing waves. The result is that each standing wave is converted into a surface emission with independent amplitude and polarization; together, the two surface emission components merge into a single free-space wave with completely controllable amplitude, phase, and polarization at each point over its wavefront.”<\/p>\n

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\"Leaky-wave
Left two figures: Two holographic images produced by a leaky-wave metasurface at two different distances from the device surface. Right four figures: Four distinct holographic images produced by a single leaky-wave metasurface at two different distances from the device surface and at two orthogonal polarization states. Credit: Heqing Huang, Adam Overvig, and Nanfang Yu\/Columbia Engineering<\/figcaption><\/figure>\n<\/div>\n<\/div>\n
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From quantum optics to optical communications to holographic 3D displays<\/h2>\n

Yu’s team experimentally demonstrated multiple leaky-wave metasurfaces that can convert 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 about 300 times the wavelength at the telecom wavelength of 1.55 microns. These include:<\/p>\n