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Volume 48, Issue 8
Editor’s Choice on Innovative Researches in Laser Engineering
Displaying 1-9 of 9 articles from this issue
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Fumihiko KANNARI2020 Volume 48 Issue 8 Pages 402-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSFrom the recent laser research, we have uncovered some new research trends that could be expected to develop new, where the researcher population is not large yet and planned a special issue with an a la carte menu. With this type of new special edition policy, we hope to continue to introduce new laser research trends to the society members.View full abstractDownload PDF (209K) -
Satoshi IWAMOTO, Yasutomo OTA, Yasuhiko ARAKAWA2020 Volume 48 Issue 8 Pages 404-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSTopological photonics, an emerging field in photonics, is now receiving much attention not only due to its fundamental interests but also potential applications in integrated photonics. The concept of band topology originally developed in condensed matter physics provides a novel route for controlling light wave in periodic optical systems such as photonic crystals. Here, we try to give readers a rough idea of what topological photonics is. Starting with a brief overview of the field, we will explain the fundamental concept “without” using any equations. Then, we will introduce the three possible topological two-dimensional photonic crystals. Among them, valley photonic crystal, which can be simply realized based on semiconductor nanophotonics, will be discussed in detail.View full abstractDownload PDF (1667K) -
Masaki YUMOTO, Norihito SAITO, Satoshi WADA2020 Volume 48 Issue 8 Pages 409-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSCr 2+ doped II-VI chalcogenides (Cr:ZnSe, Cr:ZnS, Cr:CdSe, etc.) are attractive laser media for direct access to the mid-infrared (MIR) region, because they possess a broad fluorescence spectrum and a large stimulated-emission cross section. Using them as laser media allows us to obtain superb tunable laser and femtosecond laser capabilities in the mid-IR region. In this paper, we review the optical properties of Cr 2+ doped II-VI chalcogenides, pump sources, the recent progress of Cr 2+ doped II-VI chalcogenide lasers, and our mid-IR lasers based on Cr:ZnSe and Cr:CdSe.View full abstractDownload PDF (833K) -
Makoto HIROSE , Yukio TAKAHASHI2020 Volume 48 Issue 8 Pages 414-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSPtychography is an emerging scanning lensless microscopy that can simultaneously visualize both the object function and the illumination field from multiple coherent diffraction patterns. In the X-ray region, the fabrication accuracy of the lens is already approaching its technical limitation, and hence, ptychography is regarded as a promising technique for the high-spatial-resolution imaging of bulk materials. A combination of X-ray ptychography and X-ray absorption spectroscopy, called X-ray spectro-ptychography, can also provide information on the chemical state and/or the atomic arrangement at the nanoscale by reconstructing the spatially-resolved X-ray Absorption Fine Structure (XAFS) spectra. However, the measurement of nanoscale XAFS is challenging due to its small absorption cross section, especially in the hard X-ray region. Here, we introduce the basic principle of X-ray ptychography and report the recent progress on the development and the application of hard X-ray spectro-ptychography.View full abstractDownload PDF (1820K) -
Mihoko MARUYAMA, Hiroshi Y. YOSHIKAWA, Yuka TSURI, Masashi YOSHIMURA,, ...2020 Volume 48 Issue 8 Pages 419-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSA new innovation in crystallization techniques using a femtosecond laser, of which the authors have been developing for in this decade, is reviewed. We first introduce a novel selective crystallization method of the metastable phase of pharmaceutical compounds with cavitation bubbles induced by femtosecond laser irradiation. Surprisingly, the metastable phase obtained by this method possesses high temporal stability, and thus, the method can be promising in producing new medicines. We also describe our recent development in spatio-temporal control of crystal growth by femtosecond laser ablation, which enables us to promote the growth of various organic crystals including protein crystals. We also explain the underlying mechanism from the viewpoint of crystal growth mode. we expect these laser methods will be applied to various scientific and industrial fields related to crystallization.View full abstractDownload PDF (1804K) -
Chiaki SASAOKA, Hiroshi AMANO2020 Volume 48 Issue 8 Pages 427-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSA UV-C laser diode is a promising light source for processing and machining applications due to photon energy near 5 eV. Recently, our group reported a 272-nm laser diode (LD) fabricated on a high-quality AlN substrate. Several key technologies are involved to achieve lasing; a low-dislocation-density AlN substrate to reduce waveguide optical loss, and distributed polarization doping to increase the hole density in the p-side AlGaN cladding of high Al composition. After introducing these key technologies, we describe a highly productive on-wafer laser fabrication process in which a facet mirror is prepared by dry- and wet-etching and coated with atomic layer deposited DBR (Distributed Bragg Reflector). These technologies are expected to open up new UV-C applications and be widely implemented around the world.View full abstractDownload PDF (1895K) -
Daiji MORITA, Nobuhiro SHINOHARA, Yoshikazu NAKANO, Takashi HASHIM ...2020 Volume 48 Issue 8 Pages 431-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSAmid increases for low-volume production, additive manufacturing is being used to produce metal parts, especially for aircraft and automobiles, because it eliminates the cost-bearing need for jigs and assemblies and improves design freedom. When additive manufacturing is done with lasers, they can be used to melt and deposit the material. The heat generated by the laser and from the just deposited material is transferred to the deposition base. If a new molten material is deposited on this extra-hot base, solidification might take time, during which the shape can collapse. To prevent such heat problems, Mitsubishi Electric ensured adequate cooling time by combining unique laser and CNC (computerized numerical control) technologies: a pulsed laser and minimized heat input. Shape accuracy is 70% more precise with new dot-forming technology that synchronously controls the supply of wires and shield gas as well as the position and moving speed of the laser irradiation point. Since high temperatures are limited to a point-like narrow area, the antioxidant action of the shield gas spreads over the entire high-heat area to suppress oxidation.View full abstractDownload PDF (847K) -
Muneaki HASE2020 Volume 48 Issue 8 Pages 436-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSNitrogen-vacancy (NV) center in diamond crystals offers high spatial-resolution quantum sensing based on controllable photo-luminescence under microwave irradiation. In order to explore possible development of NV centers toward nonlinear quantum sensing, we investigate the effect of NV centers in single crystal diamond on nonlinear optical effects using 40 fs femtosecond laser pulses. The near-infrared femtosecond pulses allow us to study purely nonlinear optical effects, such as optical Kerr effect (OKE) and two-photon absorption (TPA). We found that both nonlinear optical effects are significantly enhanced by the introduction of NV centers. In particular, our data demonstrate that the OKE signal is strongly enhanced for the heavily implanted type-IIa diamond, being possibly originated from cascading OKE, where the high-density NV centers break the spatial inversion symmetry near the surface region of diamond.View full abstractDownload PDF (1429K) -
Hisayoshi YURIMOTO, Ken-ichi BAJO2020 Volume 48 Issue 8 Pages 441-
Published: 2020
Released on J-STAGE: October 25, 2022
JOURNAL FREE ACCESSAn isotope nanoscope analyzing He in solid materials has been developed, applying secondary neutral mass spectrometry combined with tunneling post-ionization by femto-second laser. The isotope nanoscope achieved spatial resolutions of 10 nm for all trace elements including He in solids. NASA Genesis spacecraft collected solar wind into high-purity solid materials and returned it to the Earth. Depth profiling of Genesis solar wind collector by the isotope nanoscope firstly analyzed speed distribution of solar wind He in the laboratory. From the depth profiling, we found that solar wind of CME in October, 2003 reached the speed of 2500 km s- 1, which has not ever recorded by satellite observations.View full abstractDownload PDF (1504K)
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