Image courtesy of Lawrence Berkeley National Laboratory
Left: Scanning electron microscope image of a silicon surface hosting a nano-scale array of V-shaped gold antennas (metasurface) with different lengths, orientations, and angles. Right: The antenna array forces linearly polarized light traveling through it into a curved trajectory, resulting in components with different circular polarization (red and blue) to move in opposite directions a quantum-optical phenomena called the “photonic spin Hall effect,”.
A two-dimensional array of nano-sized gold antennas with various geometries positioned on a silicon surface, an example of a “metamaterial,” can generate and amplify a usually minute, quantum-level property of light (called the photonic spin Hall effect) sufficiently to be observable with a simple camera.
The ability of metamaterials to tailor and control measureable changes in the quantum properties of light can be exploited for optical information processing and communication. Moreover, metamaterials with nano-sized antennas have the potential to shrink such photonic devices to the nanometer range.
Combining quantum-based optics with artificial nanostructures has resulted in a breakthrough that could play a prominent role in the future of computing by manipulating photon spin and obital momentum energy transfer by which quantum information can be coded. One possible route forward involves the use of metamaterials -- artificial materials comprising precisely controlled assemblies of multiple structural elements that collectively have properties unachievable with conventional materials, in part by incorporating structural elements that are smaller than the wavelength of the light they affect. Researchers from the Lawrence Berkeley National Laboratory and the University of California-Berkeley designed a metamaterial surface consisting of V-shaped, nano-sized gold antennas engineered to generate an effect on the quantum particles of light (photons) making up the beam somewhat akin to a spinning baseball passing through the air, thereby curving it to the left or right, depending on the spin. Photonic spin Hall effect has been very weak and notoriously difficult to observe. In the metamaterial system, light passing through the antenna array exhibited this photonic spin Hall effect and boosting enough to observe it using a simple camera. The future prospects for this type of material system for photon-based information processing and communication are promising.
Materials Sciences Division, Lawrence Berkeley National Laboratory
Berkeley, CA 94720
Department of Energy, Office of Science, Basic Energy Sciences program, including support of the Molecular Foundry for electron lithography. One author (J Rho) had support from the Samsung Scholarship Foundation, Republic of Korea.
X. Yin, Z. Ye, J. Rho, Y. Wang, and X. Zhang, “Photonic Spin Hall Effect at Metasurfaces.” Science 339, 1405, 2013. [DOI: 10.1126/science.1231758]
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