Yasushi Fujimoto

Bio: Yasushi Fujimoto is an academic researcher from Osaka University. The author has contributed to research in topics: Laser & Fiber laser. The author has an hindex of 27, co-authored 156 publications receiving 2933 citations. Previous affiliations of Yasushi Fujimoto include East Tennessee State University & Hamamatsu Photonics.

Infrared Luminescence from Bismuth-Doped Silica Glass

Abstract: A new infrared luminescence from bismuth-doped silica glass is discovered. Spectroscopic properties of this glass are different from those of previously reported Bi2+- or Bi3+-doped glasses or crystals. Its luminescence spectrum is wide (full-width at half maximum; about 200 nm), with the peak at 1140 nm with 500 nm excitation. Absorption bands exist between the visible and near-infrared region. The lifetime of bismuth-doped silica glass is 630 µs at room temperature, which is longer than the lifetimes of Bi3+ luminescence reported previously.

Optical amplification in bismuth-doped silica glass

Abstract: We demonstrated an amplification phenomenon in a bismuth-doped silica glass at 1.3 μm with 0.8-μm excitation. This luminescent material is a promising candidate for use as the core-fiber material of an optical amplifier at the natural zero-dispersion wavelength (1.3 μm) of silica glass fiber.

Optical properties and Faraday effect of ceramic terbium gallium garnet for a room temperature Faraday rotator.

Abstract: The optical properties, Faraday effect and Verdet constant of ceramic terbium gallium garnet (TGG) have been measured at 1064 nm, and were found to be similar to those of single crystal TGG at room temperature. Observed optical characteristics, laser induced bulk-damage threshold and optical scattering properties of ceramic TGG were compared with those of single crystal TGG. Ceramic TGG is a promising Faraday material for high-average-power YAG lasers, Yb fiber lasers and high-peak power glass lasers for inertial fusion energy drivers.

Cryogenic temperature characteristics of Verdet constant on terbium gallium garnet ceramics

Abstract: As the first demonstration of Faraday effect in a TGG ceramics, its Verdet constant at 1053 nm is evaluated to be 36.4 rad/Tm at room temperature which is same as that of the single crystal. In addition, the temperature dependence of Verdet constant is obtained experimentally. At liquid helium temperature, it is 87 times greater than that at room temperature.

Self-assembly of broadband white-light emitters.

Abstract: We use organic cations to template the solution-state assembly of corrugated lead halide layers in bulk crystalline materials. These layered hybrids emit radiation across the entire visible spectrum upon ultraviolet excitation. They are promising as single-source white-light phosphors for use with ultraviolet light-emitting diodes in solid-state lighting devices. The broadband emission provides high color rendition and the chromaticity coordinates of the emission can be tuned through halide substitution. We have isolated materials that emit the "warm" white light sought for many indoor lighting applications as well as "cold" white light that approximates the visible region of the solar spectrum. Material syntheses are inexpensive and scalable and binding agents are not required for film deposition, eliminating problems of binder photodegradation. These well-defined and tunable structures provide a flexible platform for studying the rare phenomenon of intrinsic broadband emission from bulk materials.

Petawatt and exawatt class lasers worldwide

Abstract: In the 2015 review paper 'Petawatt Class Lasers Worldwide' a comprehensive overview of the current status of highpower facilities of >200 TW was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multidisciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.

Infrared Luminescence from Bismuth-Doped Silica Glass

Abstract: A new infrared luminescence from bismuth-doped silica glass is discovered. Spectroscopic properties of this glass are different from those of previously reported Bi2+- or Bi3+-doped glasses or crystals. Its luminescence spectrum is wide (full-width at half maximum; about 200 nm), with the peak at 1140 nm with 500 nm excitation. Absorption bands exist between the visible and near-infrared region. The lifetime of bismuth-doped silica glass is 630 µs at room temperature, which is longer than the lifetimes of Bi3+ luminescence reported previously.

A new-generation color converter for high-power white LED: transparent Ce3+:YAG phosphor-in-glass

Abstract: Currently, the major commercial white light-emitting diode (WLED) is the phosphor-converted LED made of the InGaN blue-emitting chip and the Ce3+:Y3Al5O12 (Ce:YAG) yellow phosphor dispersed in organic epoxy resin or silicone. However, the organic binder in high-power WLED may age easily and turn yellow due to the accumulated heat emitted from the chip, which adversely affects the WLED properties such as luminous efficacy and color coordination, and therefore reduces its long-term reliability as well as lifetime. Herein, an innovative luminescent material: transparent Ce:YAG phosphor-in-glass (PiG) inorganic color converter, is developed to replace the conventional resin/silicone-based phosphor converter for the construction of high-power WLED. The PiG-based WLED exhibits not only excellent heat-resistance and humidity-resistance characteristics, but also superior optical performances with a luminous efficacy of 124 lm/W, a correlated color temperature of 6674 K and a color rendering index of 70. This easy fabrication, low-cost and long-lifetime WLED is expected to be a new-generation indoor/outdoor high-power lighting source.

Inertial-confinement fusion with lasers

Abstract: The quest for controlled fusion energy has been ongoing for over a half century. The demonstration of ignition and energy gain from thermonuclear fuels in the laboratory has been a major goal of fusion research for decades. Thermonuclear ignition is widely considered a milestone in the development of fusion energy, as well as a major scientific achievement with important applications in national security and basic sciences. The US is arguably the world leader in the inertial confinement approach to fusion and has invested in large facilities to pursue it, with the objective of establishing the science related to the safety and reliability of the stockpile of nuclear weapons. Although significant progress has been made in recent years, major challenges still remain in the quest for thermonuclear ignition via laser fusion. Here, we review the current state of the art in inertial confinement fusion research and describe the underlying physical principles. The quest for energy production from controlled nuclear fusion reactions has been ongoing for many decades. Here, the inertial confinement fusion approach, based on heating and compressing a fuel pellet with intense lasers, is reviewed.