Abstract
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.
Highlights
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field
Metasurfaces have opened an unprecedented avenue for shaping the wavefront of the transmitted radiation and offer fascinating properties that could usher in revolutionary application oriented photonic devices, such as high resolution holograms[14,15,16,17,18,19,20,21], ultrathin flat lenses[22,23,24], anomalous reflection and refraction[25,26], and quarter wave plates[27,28]
Where U(r0) and U(r1) represent the electric fields at point R0 on the metasurface and point R1 on the image plane, respectively; Σis the virtual object region; λ is the wavelength in vacuum; n is a vector perpendicular to the image plane with the orientation shown in Fig. 1a; r01 is the distance between R0 and R1; and cos is the inclination factor
Summary
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. To calculate the phase distribution at the hologram interface, and coding this information into specific surface structures or a spatial light modulator (SLM). This approach is widely known as computer-generated holography (CGH)[32]. In most of the recent demonstrations, only the phase information has been engineered while the amplitude is kept constant, resulting in an inevitable limitation in obtaining high-resolution perfect images. We propose a novel scheme of a broadband metasurface hologram in which we simultaneously tailor the five-level amplitude and eight-level phase modulation at terahertz frequencies. The proposed metasurface hologram design with simultaneous amplitude and phase modulation broadens the horizon of conceiving new routes to realize perfect holography, which may have immense application potentials in terahertz imaging
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