There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Statistics for Spatial Data.

Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

Flat Optics With Designer Metasurfaces

Using a metasurface comprising an array of nanorods with different orientations and a backreflector, a hologram image can be obtained in the visible and near-infrared with limited loss of light intensity.

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Metasurface holograms reaching 80% efficiency

Switches, and Actuators Masahiro Irie,*,† Tuyoshi Fukaminato,‡ Kenji Matsuda, and Seiya Kobatake †Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan ‡Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

A novel holographic light-guide plate (HLGP) for the illumination of liquid crystal display is proposed in this paper. The holographic film designed for red light (632.8nm) is introduced to the top surface of the wedge-shaped light-guide plate. The backlight system with the HLGP can achieve large gain in uniform illumination. The enhanced illumination uniformity of the emanating light is measured in the experiments.

Holographic light-guide plate for LCD backlight system

For the miniaturization and the integration of a spectrometer, the imaging system of the spectrometer should be simplified. A hybrid diffractive-refractive element is designed and fabricated, which combines the functions of dispersion and imaging. The element is composed of a lens and a special hologram. The lens is just a normal plano-convex one. And the hologram is used to take the role of grating in conventional spectrometer. It is recorded by two spherical waves, and the positions of the centers of the two waves are optimized to compensate the aberrations of the element. When the element is illuminated by collimated beam, the components of a spectrum range 400 - 800 nm from the light source are dispersed and focused on a plane with good image qualities and linear arrangement of the spectrum points. Experiment results are given. The element could be designed freely in size to be applied in various types of spectroscopic analysis systems.

Hybrid diffractive-refractive element for spectrum imaging

The volume holographic correlator can be used in the fast scene matching. However, the traditional volume holographic
recognition method is unable to implement rotation-invariant scene matching. In the multi-sample parallel estimation
method, the intensity of the multiple correlation spots can also reflect the information of the rotation angle between the
target image and the template image. Thus it can be used to derive the rotation angle in the post processing and the
rotation-invariant scene matching can be realized. The function between the rotation angle and the intensity value of the
correlation spots is presented. The experimental results show the validity of the proposed method. The rotation angle of
the target image can be precisely derived and the maximum rotation angle is as big as five degree. This method is able to
save much capacity of the volume holographic correlator, enlarge the scene matching scope and improve the recognition
accuracy.

Rotation-invariant scene matching with multi-sample parallel estimation in volume holographic correlator

White Cell is a typical multiple-path absorption cell for absorption spectroscopy. For multi-path enhanced absorption
application, we should make sure that the input light of the multiple-path cell can be output as much as possible to
enhance absorption signal. Thus the astigmatism of the White cell should be analyzed for optimization as a key factor. In
White cell, the astigmatism is difficult to be calculated as the meridian and sagittal planes of the beam would rotate with
a different angle while at each reflection. In this article, the White cell is presented by defined 4×4 optical matrices as a
nonsymmetrical system. The astigmatic difference would then be obtained from the eigenvalues of the partitioned
matrices. The numerical computation and ray-tracing simulation results presented have proved the efficiency of this
method. The astigmatism can be improved by properly choosing the distance h between the two rows of image spots on
the field mirror.

Astigmatism analysis by matrix methods in white cells

A novel configuration for a reflection Zernike phase contrast microscope is given that has a height sensitivity of 0.5 A.

Guofan Jin

Papers

Holographic light-guide plate for LCD backlight system

Hybrid diffractive-refractive element for spectrum imaging

Rotation-invariant scene matching with multi-sample parallel estimation in volume holographic correlator

Astigmatism analysis by matrix methods in white cells

Reflection Zernike phase contrast microscope