Spatial light modulators are essential optical elements in applications that require the ability to regulate the amplitude, phase and polarization of light, such as digital holography, optical communications and biomedical imaging. With the push towards miniaturization of optical components, static metasurfaces are used as competent alternatives. These evolved to active metasurfaces in which light-wavefront manipulation can be done in a time-dependent fashion. The active metasurfaces reported so far, however, still show incomplete phase modulation (below 360°). Here we present an all-solid-state, electrically tunable and reflective metasurface array that can generate a specific phase or a continuous sweep between 0 and 360° at an estimated rate of 5.4 MHz while independently adjusting the amplitude. The metasurface features 550 individually addressable nanoresonators in a 250 × 250 μm2 area with no micromechanical elements or liquid crystals. A key feature of our design is the presence of two independent control parameters (top and bottom gate voltages) in each nanoresonator, which are used to adjust the real and imaginary parts of the reflection coefficient independently. To demonstrate this array’s use in light detection and ranging, we performed a three-dimensional depth scan of an emulated street scene that consisted of a model car and a human figure up to a distance of 4.7 m.
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The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
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We appreciate the support of N. Han, J.-Y. Hwang, B. J. Kim, M. K. Lee, D.-K. Nam, Y.-H. Cho, S.-K. Cho, G. Kim, H.-E. Lee, B. I. Yoo, S. Rhee, J.-J. Han and Y.-C. Cho. We thank H. A. Atwater for insightful discussions.
J.P., J. Kyoung, S.I.K., C.S., B.G.J. and B.L.C. are inventors on US patent 10,670,941 held and submitted by Samsung Electronics that covers the use of the two-control-parameter approach for active wavefront manipulation and control. The authors declare no other competing interests.
Peer review information Nature Nanotechnology thanks Luke Sweatlock, Jason Valentine and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended Data Fig. 1 Complete coverage of the phase and the amplitude (reflectivity) for arbitrary generation of a desired reflection coefficient.
a, Reflected phase map on the color scale obtained by running full field simulation with the conditions given in Fig. 2e and varying Vt from −3 V to 2.25 V and Vb from 4.05 V to 5.2 V: if (Vt, Vb) = (0.5 V, 4.6 V) is considered approximately as a reference origin, the result shows the full 360° phase coverage for every concentric ring, for example, along the loop made by the white dashed circular arrow, within the region of interest indicated by the black dashed boundary. b, Reflectivity map on the color scale for the same voltage ranges: every pseudo-circular annulus (or concentric ring) formed by a single color represents an identical reflectivity. When each of these annuli is superposed on top of the reflection-phase map shown in a, it becomes clear that for every amplitude, it is possible to find a voltage combination (Vt, Vb) that leads to any desired phase between 0 and 360°, allowing arbitrary generation of a desired reflection coefficient.
Extended Data Fig. 2 Phase-only and amplitude-only modulations using the two-control-parameter approach.
a, A set of voltage combinations selected for the phase-only modulation or the constant-amplitude and 0–360º phase shift. b, Trajectory of the reflection coefficients for the phase-only modulation: it makes a circular ring around the origin, showing the 0–360º phase shift. c, Real part of the electrical field along the x-axis, showing the gradual phase shift that eventually builds up to 360º. d, A set of voltage combinations selected for the amplitude-only modulation. e, Corresponding phasor trajectory that clearly exhibits the constant phase while varying the amplitude from 0 to its full value. f, Real part of the electrical field along the x-axis, showing no change in the phase while the intensity gradually increases.
Numerically calculated complex reflection coefficient used in Fig. 2e showing the independent control between the phase and amplitude.
Experimentally measured reflection phase and intensity for twelve voltage combinations used in Fig. 3f showing the 360º-phase change with uniform intensity.
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Park, J., Jeong, B.G., Kim, S.I. et al. All-solid-state spatial light modulator with independent phase and amplitude control for three-dimensional LiDAR applications. Nat. Nanotechnol. 16, 69–76 (2021). https://doi.org/10.1038/s41565-020-00787-y
Nature Nanotechnology (2021)
Nature Nanotechnology (2021)
Frontiers of Optoelectronics (2021)