Inertial confinement fusion (ICF) is an approach to fusion that relies on the inertia of the fuel mass to provide confinement. To achieve conditions under which inertial confinement is sufficient for efficient thermonuclear burn, a capsule (generally a spherical shell) containing thermonuclear fuel is compressed in an implosion process to conditions of high density and temperature. ICF capsules rely on either electron conduction (direct drive) or x rays (indirect drive) for energy transport to drive an implosion. In direct drive, the laser beams (or charged particle beams) are aimed directly at a target. The laser energy is transferred to electrons by means of inverse bremsstrahlung or a variety of plasma collective processes. In indirect drive, the driver energy (from laser beams or ion beams) is first absorbed in a high‐Z enclosure (a hohlraum), which surrounds the capsule. The material heated by the driver emits x rays, which drive the capsule implosion. For optimally designed targets, 70%–80% of the d...

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Development of the indirect‐drive approach to inertial confinement fusion and the target physics basis for ignition and gain

Emerging challenges and materials for thermal management of electronics

The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of C3N4 has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nc-TiN/SiNx nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of de...

https://mediatum.ub.tum.de/doc/958917/file.pdf

The search for novel, superhard materials

Materials emitting light in the deep ultraviolet region around 200 nanometers are essential in a wide-range of applications, such as information storage technology, environmental protection, and medical treatment Hexagonal boron nitride (hBN), which was recently found to be a promising deep ultraviolet light emitter, has traditionally been synthesized under high pressure and at high temperature We successfully synthesized high-purity hBN crystals at atmospheric pressure by using a nickel-molybdenum solvent The obtained hBN crystals emitted intense 215-nanometer luminescence at room temperature This study demonstrates an easier way to grow high-quality hBN crystals, through their liquid-phase deposition on a substrate at atmospheric pressure

http://science.sciencemag.org/content/sci/317/5840/932.full.pdf

Deep Ultraviolet Light-Emitting Hexagonal Boron Nitride Synthesized at Atmospheric Pressure

Until now, micrometer-scale or larger crystals of the III-V semiconductors have not been grown at low temperatures for lack of suitable crystallization mechanisms for highly covalent nonmolecular solids. A solution-liquid-solid mechanism for the growth of InP, InAs, and GaAs is described that uses simple, low-temperature (≤203°C), solution-phase reactions. The materials are produced as polycrystalline fibers or near-single-crystal whiskers having widths of 10 to 150 nanometers and lengths of up to several micrometers. This mechanism shows that processes analogous to vapor-liquid-solid growth can operate at low temperatures; similar synthesis routes for other covalent solids may be possible.

https://science.sciencemag.org/content/sci/270/5243/1791.full.pdf

Solution-Liquid-Solid Growth of Crystalline III-V Semiconductors: An Analogy to Vapor-Liquid-Solid Growth

On the basis of the anionic group theory, a new nonlinear optical crystal cesium triborate, (CsB3O5, CBO) was discovered. Single crystals of CBO in centimeter size were grown from a stoichiometric melt. The transparent range of CBO covers from 170 to 3000 nm. The preliminary measurement of its second harmonic generation coefficient shows that its d14 is ∼0.468×d11 (β−BaB2O4). Its measured damage threshold is as high as 26 GW/cm2 at 1.053 μm, 1.0 ns.

CsB3O5: A new nonlinear optical crystal

The development of nonlinear optical (NLO) borate crystals for generation of visible and UV light is reviewed. We first discussed on the basic principles of laser frequency conversion. Then, we examine the trends in research on NLO crystals. The background and present status of NLO borate crystals are summarized. The main considerations are focused on the discussion of crystals like CsLiB6O10 (CLBO), GdxY1−xCa4O(BO3)3 (GdYCOB) and K2Al2B2O7 (KAB). Properties of related materials like β-BaB2O2 (BBO), LiB3O5 (LBO), KBe2BO3F2 (KBBF), Sr2Be2BO7 (SBBO), CsB3O5 (CBO), GdCa4O(BO3)3 (GdCOB) and YCa4O(BO3)3 (YCOB) are included for comparison. We aim to provide a complete view of developing a new NLO borate material for actual laser applications. This review covers various aspects including the search for new materials, the growth of bulk crystals, the characterization of crystal properties as well as the development of new techniques to overcome obstacles in actual laser application, namely, thermal dephasing and laser-induced damage. Finally, perspectives on NLO borate crystals and all-solid-state UV lasers are evaluated.

Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light

We report on the growth of GdCa4O(BO3)3 (GdCOB) and YCa4O(BO3)3 (YCOB) crystals and their characterization as new nonlinear optical materials. The crystals with good optical quality were grown by the Czochralski method. YCOB, the characteristics of which has not previously been reported to our knowledge, has a larger temperature acceptance bandwidth than that of GdCOB, and third harmonic generation of a Nd:YAG laser in this crystal was demonstrated.

https://iopscience.iop.org/article/10.1143/JJAP.36.L276/pdf

Crystal Growth and Optical Characterization of Rare-Earth (Re) Calcium Oxyborate ReCa4O(BO3)3 (Re=Y or Gd) as New Nonlinear Optical Material.

Preface INTRODUCTION History of the Theoretical Understanding for Nonlinear Optical Crystals History of Development on Nonlinear Optical Borate Crystals Crystal Growth of Nonlinear Borate Crystals and Current Status of Applications THEORETICAL BASIS TO DEVELOP BORATE NONLINEAR OPTICAL CRYSTALS BORATE NONLINEAR OPTICAL CRYSTALS FOR FREQUENCY CONVERSION BBO LBO Family KBBF Family Other Borate Crystals Borate Crystals in Developing APPLICATIONS Rapid Proto-Typing Semiconductor Industry - Bia-Hole Drilling - Annealing - Marking - Inspection Bio-Medical Applications - Eye Surgery - Protein Processing Advanced Instrument Making

Nonlinear optical borate crystals : principles and applications

A new nonlinear optical (NLO) borate crystal K2Al2B2O7 (Potassium Aluminum Borate, KAB) has been discovered. The structure has been established by 4-axis X-ray diffraction methods. The material crystallizes in the trigonal space group P321 with a = 8.5657(9) A, C = 8.463(2) A and Z = 3. KAB possesses a space arrangement similar to Sr2Be2B2O7 (SBBO). A KAB crystal with a dimensions of 30×15×1 mm3 was grown using the Top-Seeded Solution Growth (TSSG) method. The optical properties of KAB were measured.

https://iopscience.iop.org/article/10.1143/JJAP.37.L1093/pdf

Takatomo Sasaki

Papers

CsB3O5: A new nonlinear optical crystal

Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light

Crystal Growth and Optical Characterization of Rare-Earth (Re) Calcium Oxyborate ReCa4O(BO3)3 (Re=Y or Gd) as New Nonlinear Optical Material.

Nonlinear optical borate crystals : principles and applications

A New Nonlinear Optical Borate Crystal K2Al2B2O7 (KAB)