Abstract

Biography

Abstract

Biography

Heon Lee

Department of Materials Science and Engineering, Korea University；Zerc Co. Ltd., Korea

Email: heonlee@korea.ac.kr

    Nowadays, meta-surface, including meta-lens and meta-hologram devices, has been intensively studied by many research groups, since they can replace the existing optical system with an improved performance and a reduced form-factor. Meta-surface consists of 2 dimensional array of nano-antenna which are smaller than an operating wavelength and each nano-antenna can control the phase and amplitude of incoming light. Regardless of various researches about meta-surface, it is not commercialized yet and the biggest obstacle in commercializing meta-surface is difficulty in fabricating meta-surface in large area with reasonable cost.
    In this presentation, as large as 12-inch diameter meta-surface was fabricated by nanoimprint lithography. With a high refractive index imprint resin which is the mixture of UV curable polymer resin and high refractive index nano-particles, meta-surface was imprinted using elastomeric stamp. Meta-surface can be successfully formed on non-flat surface or flexible substrate using imprint process.
    In conclusion, the biggest hurdle for commercializing meta-surface is its high fabrication cost and limited size and these problems can be solved using nanoimprint lithography.

Tohru Sekino

SANKEN, The University of Osaka, Ibaraki, Osaka 567-0047, Japan

sekino@sanken.osaka-u.ac.jp

    Eco-materials are attracting significant attention amid today's numerous environmental and energy challenges. The science and technology of eco-materials is expected not only endow the materials themselves with functions that reduce environmental impact such as catalysts for removing harmful substances or energy generation and storage capabilities but also to contribute to reducing energy consumption by utilizing low-environmental-impact processes in the fabrication of high-performance materials and devices. This paper overviews recent material developments achieved in ceramics and inorganic materials in our group. These achievements aim to solve various current challenges through advanced tuning of structures and functions coupled with novel process development and optimization     Various nanostructured oxides could be synthesized using solution chemical processes; Titania with nanotube structures (TNT) exhibited excellent photocatalytic and environmental purification properties due to the synergistic effects of its crystal structure, low-dimensional nanostructure, and the semiconductor and chemical properties of titania. While conventional methods for TNT synthesis required excessively high-concentration alkaline aqueous solutions, novel protocol using titanium peroxide complex solutions significantly reduced alkali consumption and enabled the peroxo groups modification to the TNTs. This allows the one-pot synthesis of visible-light-responsive peroxo-modified TNT (PTNT). This nano-titania responded to visible light and induced resultant charge separation and possessed photocatalytic performance capable of selectively cleaving specific chemical bonds of organic molecules. When attempting controlled hydrothermal synthesis, alkaline titanates were formed into a seaweed-like structure, and they exhibited excellent ion adsorption properties due to their layered structure, making them promising candidates for high-performance water purification materials.     On the other hand, fabricating bulk ceramics typically requires high-temperature sintering. Recently, however, cold sintering process (CSP) utilizing localized hydrothermal reactions between compacted ceramic particles have been attracting much attention. In this research, we report CSP and modified CSP methods based on low-temperature mineralization sintering protocol (LMSP) using reaction solutions containing constituent components for materials.     These methods allowed to promote dynamic dissolution and reprecipitation of inorganic phases such as nano-glass, calcium phosphates and non-oxide (silicon nitride) to densify nanosized raw materials. As a result, we successfully fabricated dense bulk ceramics at process temperatures below 300 °C. This paper outlines the fabrication of calcium phosphate-based sintered bodies (hydroxy apatite and whitlockite) and their structure and mechanical properties, which cannot be achieved by conventional sintering methods. Low-temperature densification of silicon nitride has been achieved by using surface pre-modified raw materials with silica phases. In addition, recent research achievements applying CSP to energy device materials, such as secondary battery electrodes, will also be discussed.

Liangbi Su

Shanghai Institute of Ceramics, Chinese Academy of Sciences

Email: suliangbi@mail.sic.ac.cn

    Optical functional crystals play an irreplaceable role in the development of laser technologies, semiconductor industries, high-end equipment manufacturing, etc. In the current era, the demands from both the scientific frontiers and the megaprojects are continuously driving the developments of optical functional crystals to overcome bottlenecks in the scaling of crystal sizes, the suppression of crystal defects and the improvement of the device performances. Such innovation-driven attempts are pushing the crystal growth and defect control of optical functional crystals towards the boundaries, in order to achieve ultra-large dimensions, ultra-low defects and extreme performances. Our research focuses on the design, crystal growth and characterizations of novel fluoride optical functional crystals for critical applications in fields such as lasers and high-precision optics: (1) We proposed the strategy of designing the luminescent behaviors of rare earth doped MF2 (M=Ca, Sr, Ba) crystals by tailoring the local coordinate structure via co-doping buffer ions. Special crystal lattice orders, i.e., “short-range disordered structures” embedded within the long-term periodic lattices, are created by manipulating the site environments of the rare earth dopants. A series of new laser crystals with performance exceeding that of traditional laser materials have been developed, establishing a new paradigm for the design of new laser crystals for diverse laser applications. (2) An in-situ observation method for real-time visualization of crystal growth interfaces was developed based on a conventional vertical Bridgman (VB) apparatus for fluoride crystal growth. The crucial bottlenecks of conventional crystal growth, i.e., the crystallization interfaces are neither detectable nor controllable, were overcome by establishing a feedback control system for maintaining stable solid-liquid (S-L) crystal growth interfaces with optimized shape, based on the capability to achieve quantitative information about the crystal growth processes by extracting the coordinates of S-L interfaces. Large-scale fluoride laser and optical crystals with high optical quality were successfully grown. (3) A series of breakthroughs in laser performances were achieved: in the ~1 μm spectral region, the laser pulse duration of solid-state laser based on Nd3+ doped fluoride crystals was suppressed to sub-100 fs range for the first time; in the ~2 μm spectral region, CW laser of a slope efficiency over 80% was realized using Tm:SrF2 crystals, corresponding to a quantum efficiency close to 200%; in the ~3 μm spectral region, high efficiency CW laser with the output power exceeding 15 watts was generated, which is to our best knowledge the highest record for CW mid-infrared lasers achieved in rare earth doped crystals. The outstanding laser performances indicate that these fluorite-type laser crystals are promising candidates for high-performance solid-state laser applications.