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 developed, binary, image-processing technique is proposed, and a dual-channel, optical, real-time morphological processor is developed. Nine binary image processings can be realized fully in parallel. The measures for compensating scale and rotation distortion for pattern recognition are provided. Some applications of optical, morphological binary image processing are studied and experimental results are listed.

Developed, binary, image processing in a dual-channel, optical, real-time morphological processor

Wavelet and harmonic filtering for distortion-invariant volume holographic correlation

A short-focal-length double-Fourier-transform-lens system for holographic storage was designed. The system is minimized by propagating signal beam and reference beam along a common optical axis. In order to obtain a compact configuration and high information density, the front and the rear Fourier-transform lens have short focal length (33 and 30 mm, respectively). The multiconfiguration optimization method is adopted to correct aberrations of the object region and meet the requirement of reference beam. The designed system, whose total numerical aperture for signal beam and reference beam is 0.60, achieves diffraction-limited imaging quality.

Design of a short-focal-length double-Fourier-transform-lens system for holographic storage

We demonstrate an ambient light coherent anti-Stokes Raman scattering microscope that allows CARS imaging to be operated under environmental light for field use. The CARS signal is modulated at megahertz frequency and detected by a photodiode equipped with a lab-built resonant amplifier, then extracted through a lock-in amplifier. The filters in both the spectral domain and the frequency domain effectively blocked the room light contamination of the CARS image. In situ hyperspectral CARS imaging of tumor tissue under ambient light is demonstrated.

Coherent anti-Stokes Raman scattering imaging under ambient light.

In this paper, we have proposed an innovative model of freeform illumination design, which differs from the current model that covers almost all of the existing freeform illumination systems. In our model, a freeform illumination system is designed for multiple light sources simultaneously, rather than just for one certain source like the current model. All the sources have the same size, shape, intensity distribution, and other photometric characteristics, but are located at different positions or directions. Each source can individually achieve an illumination pattern on the target plane. All the patterns are expected to have the same size, shape, and illuminance distribution, but the position of each pattern has a linear relationship with the position or direction of the corresponding source. Two new (to our knowledge) illumination functions can be realized in our model, as the light sources are non-single and movable. The first one is the continuous scanning of the illumination pattern on the target plane, and the second one achieves a flexible, diverse, and controllable array of illumination patterns on the target plane. As an example, a coaxial freeform illumination system has been designed under the framework of this model, in which multiple collimated light sources are introduced simultaneously. The design method and process of the system are presented. The system is further promoted, and the two new illumination functions are explained in detail based on the design example.

Guofan Jin

Papers

Developed, binary, image processing in a dual-channel, optical, real-time morphological processor

Wavelet and harmonic filtering for distortion-invariant volume holographic correlation

Design of a short-focal-length double-Fourier-transform-lens system for holographic storage

Coherent anti-Stokes Raman scattering imaging under ambient light.

Freeform illumination design model for multiple light sources simultaneously