Phase-gradient gap-plasmon metasurface based blazed grating for real time dispersive imaging

Abstract

Dispersive Fourier transform imaging is a powerful technique in achieving ultrafast imaging of wide areas. However, system power efficiency is often limited by dispersive components. Here, we demonstrate that a gap-plasmon metasurface (GPM) based blazed grating can be used in dispersive imaging applications to achieve higher power efficiency than conventional gratings. A sub-wavelength GPM-based grating at telecommunication wavelengths has been designed and fabricated. 75.6% power efficiency with ∼0.4°/10 nm spatial dispersion has been measured for TE polarized waves at normal incidence. The fabricated device has been tested in a wide area real-time dispersive imaging system and <300 μm spatial resolution has been demonstrated experimentally.

Fundamental limits of ultrathin metasurfaces

“…However, a multilayer metasurface might be designed such that the phase of I varies among different layers. This has been shown in the microwave regime162223242526, and more recently, at optical wavelengths1827282930. Nevertheless, since the anti-symmetric term is proportional to k 1 h , for it to become comparable to the symmetric term, large values of effective current density are required which lead to large absorption losses.…”

Terahertz Wavefront Control by Graphene Metasurface

“…Numerical simulations reveal that wide-angle beam steering up to 53° with a reflection 730 efficiency as high as 60% is achieved at 5 THz within a switching time shorter than 0.6 ps. Our reflection-type graphene metasurfaces offer both high power efficiency and high-speed operation for a variety of potential applications, such as spatial phase modulation, beam shaping, and imaging system [30]. Hence this approach may open up new avenues for achieving total manipulation of radiation in the THz and infrared region.…”

Ultrawide Angle, Directional Spectrum Splitting with Visible‐Frequency Versatile Metasurfaces

“…[2][3][4][5][6][7][8] Typical metasurfaces consist of spacevariant subwavelength resonators [9][10][11] that introduce a gradual or abrupt interfacial phase shift for incident wavefront [ 12,13 ] and thus mani pulating outgoing light to a certain direction. [ 14 ] Flat optical devices based on metasurfaces (Figure 1 c) have been demonstrated to anomalously steer single wavelength or broadband illumination [ 15,16 ] and enable beam-splitting [ 17 ] functionality as similar to blazed gratings. [ 14,18 ] Such photonic spatial separation and beam splitting effects for multi-wavelength are signifi cant for various applications including spectrometers and spectrum splitters for solar cells.…”

“…[ 14 ] Flat optical devices based on metasurfaces (Figure 1 c) have been demonstrated to anomalously steer single wavelength or broadband illumination [ 15,16 ] and enable beam-splitting [ 17 ] functionality as similar to blazed gratings. [ 14,18 ] Such photonic spatial separation and beam splitting effects for multi-wavelength are signifi cant for various applications including spectrometers and spectrum splitters for solar cells. In blazed gratings and typical metasurface-based beam-splitters, all the wavelengths are defl ected to a particular direction with a narrow angular range (usually ≈20°-30° bandwidth) as shown in Figure 1 e. [ 19 ] Here, we demonstrate both theoretically and experimentally that a virtually fl at surface based on metasurface has the versatility of steering different light frequency components (green and red light) to different directions, as shown in Figure 1 d. The unit cell of our metasurface is composed of two distinct trapezoidshaped nanoantennas that are placed opposite to each other as shown in Figure 2 a.…”