35 research outputs found
Shape dependent conformable holographic metasurfaces
Funding: European Research Council - 819346; Engineering and Physical Sciences Research Council - EP/V029975/1; Royal Society - URF\R\211033.In this paper, the design, fabrication, and experimental demonstration of conformable holographic metasurfaces are reported. Here, it is shown that the produced holographic image changes as the metasurface is applied to targets with different shapes. The demonstration is based on a reflective type metasurface, where the reflected polarization is perpendicular to that of the incident light. In addition, how the parameters of the metasurface determine the quality of the images produced and the ability to produce independent images are discussed critically.Publisher PDFPeer reviewe
Recent advances in optical metasurfaces for polarization detection and engineered polarization profiles
Like amplitude, phase and frequency, polarization is one of the fundamental properties of light, which can be used to record, process and store information. Optical metasurfaces are ultrathin inhomogeneous media with planar nanostructures that can manipulate the optical properties of light at the subwavelength scale, which have become a current subject of intense research due to the desirable control of light propagation. The unprecedented capability of optical metasurfaces in the manipulation of the lightβs polarization at subwavelength resolution has provided an unusual approach for polarization detection and arbitrary manipulation of polarization profiles. A compact metasurface platform has been demonstrated to detect polarization information of a light beam and to arbitrarily engineer a polarization profile that is very difficult or impossible to realize with conventional optical elements. This review will focus on the recent progress on ultrathin metasurface devices for polarization detection and realization of customized polarization profiles. Optical metasurfaces have provided new opportunities for polarization detection and manipulation, which can facilitate real-world deployment of polarization-related devices and systems in various research fields, including sensing, imaging, encryption, optical communications, quantum science, and fundamental physics
Numerical techniques for Fresnel diffraction in computational holography
Optical holography can produce very realistic virtual images due to its capability to properly convey the depth cues that we use to interpret three-dimensional objects. Computational holography is the use of digital representations plus computational methods to carry out the holographic operations of construction and reconstruction. The large computational requirements of holographic simulations prohibit present-day existence of real-time holographic displays comparable in size to traditional two-dimensional displays. Fourier-based approaches to calculate the Fresnel diffraction of light provide one of the most efficient algorithms for holographic computations because this permits the use of the fast Fourier transform (FFT). The limitations on sampling imposed by Fourier-based algorithms have been overcome by the development, in this research, of a fast shifted Fresnel transform. This fast shifted Fresnel transform was used to develop a tiling approach to hologram construction and reconstruction, which computes the Fresnel propagation of light between parallel planes having different resolutions. A new method for hologram construction is presented, named partitioned hologram computation, which applies the concepts of the shifted Fresnel transform and tiling
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In this regard, this dissertation presents the metasurfaces designed to control the phases at both the transmission and reflection spaces. Compared to the conventional metasurfaces that consider only transmitted or reflected light from metasurfaces, this proposed platform enhances the information capacity of metasurface into full-space. Therefore, it can be regarded as a new paradigm in metasurface design and system design as well. Contrary to the intuitive point of view, it is designed to independently control the scattered light in full-space, especially the phase of light imparted into two spaces, with a single layer and a simple structured metasurface.
In this dissertation, total three platforms are introduced. Firstly, a novel metasurface that enables full-space light control is realized, offering an unconventional functionality that provides a new foothold for metasurface integration in optics. Multipolar interference and PancharatnamβBerry phase are combined with each other and suggested as a physical background for the proposed device. As an example of the functionality, asymmetric beam steering and hologram generation are proposed and measured experimentally. To authorβs knowledge, this is the first work achieving independent phase control of full-space in visible range.
Secondly, a metasurface platform consisting of interleaved L-shaped meta-atoms is presented. Basically, this metasurface is designed to operate by Pancharatnam-Berry phase (controlled by incident circularly polarized light) as above and transmits different phase values in the transmission and reflection directions. In addition, when the polarization handedness of the incident light is altered, the phases transmitted in each direction are designed to reverse each other, which, to authorβs knowledge, has never been proposed before.
Finally, the author presents a design method that enables polarization-dependent full-space control, in which two independent and arbitrary phase profiles can be addressed to each space. Upon introducing a phase gradient value to realize the critical angle condition, conversion of transmissive into reflective operation is realized. Then, rectangular nanopillars are utilized to facilitate polarization beam splitting with the desired phase. Three samples were fabricated and measured based on the proposed scheme.
In conclusion, this full-space control is meaningful in three ways: 1) it showed an unprecedented control method that is possible only through metasurfaces, 2) increased the amount of information that metasurfaces can have, and 3) showed potential for future optical devices through new control.Chapter 1 Introduction 1
1.1 Overview of metasurfaces for optical modulation 1
1.2 Motivation of this dissertation: metasurface for full-space control 4
1.3 Scope and Organization 9
Chapter 2 Simultaneous full-space visible light control 12
2.1 Introduction 12
2.2 Metasurface design 15
2.2.1 Design strategy and numerically calculated results 15
2.2.2 Determined structure and numerical demonstration 19
2.3 Experimental demonstration 27
2.3.1 Experimental setup and fabrication 27
2.3.2 Asymmetric beam deflection 30
2.3.3 Asymmetric hologram generation 34
2.4 Conclusion 37
Chapter 3 Polarization dependent space conversion with L-shaped meta-atom 38
3.1 Introduction 38
3.2 L-shaped meta-atom for space conversion 40
3.3 Simulation results 46
3.3.1 determined parameters and multipole decomposition 46
3.3.2 Polarization-dependent phase behavior of LSMA 51
3.4 Experimental demonstration 54
3.4.1 Unit cell determination 54
3.4.2 Hologram generation and beam deflection using LSMA 57
3.5 Conclusion 61
Chapter 4 Switching modulated space by arbitrary polarization pair 62
4.1 Introduction 62
4.2 Basic metasurface design 64
4.3 Phase gradient metasurface for reflective operation 70
4.4 Experimental demonstration 79
4.5 Conclusion 87
Chapter 5 Conclusion 89
Bibliography 94
Appendix 101λ°