Yosuke Minowa

Hokkaido University, Sapporo, Hokkaidō, Japan

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Publications (91)165.21 Total impact

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    ABSTRACT: We demonstrated an achromatic wave plate based on parallel metal plate waveguides in the high THz frequency region. The metal plates have periodic rough structures on the surface, which allow slow transverse magnetic wave propagation and fast transverse electric wave propagation. A numerical simulation showed that the height of the periodic roughness is important for optimizing the birefringence. We fabricated stacked metal plates containing two types of structures by chemical etching. An array of small pillars on the metal plates allows higher frequency optimization. We experimentally demonstrated an achromatic quarter-wave plate in the frequency region from 2.0 to 3.1 THz.
    Optics Express 02/2015; 23(4). DOI:10.1364/OE.23.004641 · 3.53 Impact Factor
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    Yosuke Minowa, Ryoichi Kawai, Masaaki Ashida
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    ABSTRACT: Semiconductor nanocrystals, also known as quantum dots (QDs), are key ingredients in current quantum optics experiments. They serve as quantum emitters and memories and have tunable energy levels that depend not only on the material but also, through the quantum confinement effect, on the size. The resulting strongly confined electron and hole wave functions lead to large transition dipole moments, which opens a path to ultra strong coupling and even deep strong coupling between light and matter. Such efficient coupling requires the precise positioning of the QD in an optical cavity with a high quality factor and small mode volume, such as micro-Fabry--Perot cavity, whispering-gallery-mode microcavity, or photonic-crystal cavity. However, the absence of a technique for free-space positioning has limited the further research on QD-based cavity quantum electrodynamics. In this paper, we present a technique to overcome this challenge by demonstrating the optical levitation or trapping in helium gas of a single QD within a liquid droplet. Bright single-photon emission from the levitated QD was observed for more than 200 s. To the best of our best knowledge, this study provides the first proof-of-principle demonstration of an optically levitated solid-state quantum emitter.
    Optics Letters 08/2014; 40(6). DOI:10.1364/OL.40.000906 · 3.39 Impact Factor
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    ABSTRACT: Current AO observations rely heavily on the AO188 instrument, a 188-elements system that can operate in natural or laser guide star (LGS) mode, and delivers diffraction-limited images in near-IR. In its LGS mode, laser light is transported from the solid state laser to the launch telescope by a single mode fiber. AO188 can feed several instruments: the infrared camera and spectrograph (IRCS), a high contrast imaging instrument (HiCIAO) or an optical integral field spectrograph (Kyoto-3DII). Adaptive optics development in support of exoplanet observations has been and continues to be very active. The Subaru Coronagraphic Extreme-AO (SCExAO) system, which combines extreme-AO correction with advanced coronagraphy, is in the commissioning phase, and will greatly increase Subaru Telescope’s ability to image and study exoplanets. SCExAO currently feeds light to HiCIAO, and will soon be combined with the CHARIS integral field spectrograph and the fast frame MKIDs exoplanet camera, which have both been specifically designed for high contrast imaging. SCExAO also feeds two visible-light single pupil interferometers: VAMPIRES and FIRST. In parallel to these direct imaging activities, a near-IR high precision spectrograph (IRD) is under development for observing exoplanets with the radial velocity technique. Wide-field adaptive optics techniques are also being pursued. The RAVEN multi-object adaptive optics instrument was installed on Subaru telescope in early 2014. Subaru Telescope is also planning wide field imaging with ground-layer AO with the ULTIMATE-Subaru project.
    SPIE Astronomical Telescopes + Instrumentation; 08/2014
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    ABSTRACT: A future plan for the next-generation Subaru adaptive optics, is a system based on an adaptive secondary mirror. A ground-layer adaptive optics combined with a new wide-field multi-object infrared camera and spectrograph will be a main application of the adaptive secondary mirror. A preliminary simulation results show that the resolution achieved by the ground-layer adaptive optics is expected to be better than 0.2 arcsecond in the K-band over 15 arcminutes field-of-view. In this paper, the performance simulation is updated taking dependence on observation conditions, the zenith angle and the season, into account.
    SPIE Astronomical Telescopes + Instrumentation; 08/2014
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    ABSTRACT: We present the result of Subaru Telescope multi-band adaptive optics observations of the complex gravitationally lensed quasar SDSS J1405+0959, which is produced by two lensing galaxies. These observations reveal dramatically enhanced morphological detail, leading to the discovery of an additional object 0. 26'' from the secondary lensing galaxy, as well as three collinear clumps located in between the two lensing galaxies. The new object is likely to be the third quasar image, although the possibility that it is a galaxy cannot be entirely excluded. If confirmed via future observations, it would be the first three image lensed quasar produced by two galaxy lenses. In either case, we show based on gravitational lensing models and photometric redshift that the collinear clumps represent merging images of a portion of the quasar host galaxy, with a magnification factor of 15 - 20, depending on the model.
    Monthly Notices of the Royal Astronomical Society 08/2014; 444(3). DOI:10.1093/mnras/stu1621 · 5.23 Impact Factor
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    ABSTRACT: The project, "ULTIMATE- SUBARU", stands for "Ultra-wide Laser Tomographic Imager and MOS with AO for Transcendent Exploration at SUBARU Telescope." ULTIMATE-SUBARU provides a wide-field near infrared instrument at Cassegrain focus with GLAO. Performance simulation of GLAO at Subaru Telescope indicates that uniform PSFs can be obtained across the field of view up to 20 arcmin in diameter. This paper describes a current status of ULTIMATE-SUBARU project, science objectives, performance simulation update, system overview, feasibility of adaptive secondary mirror, and laser system.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is one of a handful of extreme adaptive optics systems set to come online in 2014. The extreme adaptive optics correction is realized by a combination of precise wavefront sensing via a non-modulated pyramid wavefront sensor and a 2000 element deformable mirror. This system has recently begun on-sky commissioning and was operated in closed loop for several minutes at a time with a loop speed of 800 Hz, on ~150 modes. Further suppression of quasi-static speckles is possible via a process called "speckle nulling" which can create a dark hole in a portion of the frame allowing for an enhancement in contrast, and has been successfully tested on-sky. In addition to the wavefront correction there are a suite of coronagraphs on board to null out the host star which include the phase induced amplitude apodization (PIAA), the vector vortex, 8 octant phase mask, 4 quadrant phase mask and shaped pupil versions which operate in the NIR (y-K bands). The PIAA and vector vortex will allow for high contrast imaging down to an angular separation of 1 λ/D to be reached; a factor of 3 closer in than other extreme AO systems. Making use of the left over visible light not used by the wavefront sensor is VAMPIRES and FIRST. These modules are based on aperture masking interferometry and allow for sub-diffraction limited imaging with moderate contrasts of ~100-1000:1. Both modules have undergone initial testing on-sky and are set to be fully commissioned by the end of 2014.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: We have discovered that Europa, Ganymede and Callisto are bright around 1.5 {\mu}m even when not directly lit by sunlight, based on observations from the Hubble Space Telescope and the Subaru Telescope. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was $10^{-6}$-$10^{-7}$ of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was <1/10 of the others at 1.5 {\mu}m, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 {\mu}m by the Spitzer Space Telescope but it was not detected, suggesting a significant wavelength dependence. The reason why they are luminous even when in the Jovian shadow is still unknown, but forward-scattered sunlight by haze in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us a new technique to investigate Jovian atmospheric composition, and investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.
    The Astrophysical Journal 05/2014; 789(2). DOI:10.1088/0004-637X/789/2/122 · 6.28 Impact Factor
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    ABSTRACT: We searched for star formation activity associated with high-z damped Lyα systems (DLAs) with the Subaru telescope. We used a set of narrow-band (NB) filters whose central wavelengths correspond to the redshifted Lyα emission lines of targeted DLA absorbers at 3 < z < 4.5. We detected one apparent NB-excess object located 3.80 arcsec ({\sim }28\ h_{70}^{-1} kpc) away from the quasar SDSS J031036.84+005521.7. Follow-up spectroscopy revealed an asymmetric Lyα emission at z em = 3.115 ± 0.003, which perfectly matches the sub-DLA trough at z abs = 3.1150 with logN(H I)/cm–2 = 20.05. The Lyα luminosity is estimated to be L Lyα = 1.07 × 1042 erg s–1, which corresponds to a star formation rate of 0.97 M ☉ yr–1. Interestingly, the detected Lyα emission is spatially extended with a sharp peak. The large extent of the Lyα emission is remarkably one-sided toward the quasar line-of-sight and is redshifted. The observed spatially asymmetric surface brightness profile can be qualitatively explained by a model of a DLA host galaxy, assuming a galactic outflow and a clumpy distribution of H I clouds in the circumgalactic medium. This large Lyα extension, which is similar to those found in Rauch et al., could be the result of complicated anisotropic radiative transfer through the surrounding neutral gas embedded in the DLA. Based on data collected at the Subaru telescope, which is operated by the National Astronomical Observatory of Japan.
    The Astrophysical Journal 01/2014; 780(2):116-. DOI:10.1088/0004-637X/780/2/116 · 6.28 Impact Factor
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    ABSTRACT: We successfully fabricated semiconductor microspheres of ZnO, ZnSe, etc., by laser ablation in superfluid helium and investigated their morphology and optical properties. Time-resolved photoluminescence spectroscopy in ultraviolet region of single ZnO microspheres shows luminescence spectra with mode structures and remarkable reduction of the luminescence decay time compared to that of polycrystals or non-spherical microparticles. This indicates strong light-matter interaction due to efficient light-confinement in the ZnO microspheres. In addition, the fabricated ZnSe microspheres also show the photoluminescence spectra with typical mode structures indicating their high sphericity.
    MRS Online Proceeding Library 01/2014; 1635. DOI:10.1557/opl.2014.100
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    ABSTRACT: We propose a simple achromatic terahertz wave plate composed of stacked parallel metal plates with a hole array. It consists of an ensemble of designed parallel plate waveguides; the high and low propagation speeds of waves in TE and TM waveguide modes with the same group velocity cause a constant phase difference over a wide frequency region. Using that wave plate, we obtained intense single- and multi-cycle THz pulses with circular polarization.
    Optics Letters 01/2014; 39(1):146-9. DOI:10.1364/OL.39.000146 · 3.39 Impact Factor
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    ABSTRACT: We searched for star formation activity associated with high-z Damped Lyman-alpha systems (DLAs) with Subaru telescope. We used a set of narrow-band (NB) filters whose central wavelengths correspond to the redshifted Lyman-alpha emission lines of targeted DLA absorbers at 3<z<4.5. We detected one apparent NB-excess object located 3.80 arcsec (~28kpc) away from the quasar SDSS J031036.84+005521.7. Follow-up spectroscopy revealed an asymmetric Lyman-alpha emission at z_em=3.115+/-0.003, which perfectly matches the sub-DLA trough at z_abs=3.1150 with logN(HI)/cm^-2=20.05. The Lyman-alpha luminosity is estimated to be L(LyA)=1.07x10^42 erg s^-1, which corresponds to a star formation rate of 0.97 M_\odot yr^-1. Interestingly, the detected Lyman-alpha emission is spatially extended with a sharp peak. The large extent of the Lyman-alpha emission is remarkably one-sided toward the quasar line-of-sight, and is redshifted. The observed spatially asymmetric surface brightness profile can be qualitatively explained by a model of a DLA host galaxy, assuming a galactic outflow and a clumpy distribution of HI clouds in the circumgalactic medium. This large Lyman-alpha extension, which is similar to those found in Rauch et al. (2008), could be the result of complicated anisotropic radiative transfer through the surrounding neutral gas embedded in the DLA.
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    ABSTRACT: Supernovae (SNe) have been proposed to be the main production sites of dust grains in the Universe. Our knowledge on their importance to dust production is, however, limited by observationally poor constraints on the nature and amount of dust particles produced by individual SNe. In this paper, we present a spectrum covering optical through near-Infrared (NIR) light of the luminous Type IIn supernova (SN IIn) 2010jl around one and half years after the explosion. This unique data set reveals multiple signatures of newly formed dust particles. The NIR portion of the spectrum provides a rare example where thermal emission from newly formed hot dust grains is clearly detected. We determine the main population of the dust species to be carbon grains at a temperature of ~1,350 - 1,450K at this epoch. The mass of the dust grains is derived to be ~(7.5 - 8.5) x 10^{-4} Msun. Hydrogen emission lines show wavelength-dependent absorption, which provides a good estimate on the typical size of the newly formed dust grains (~0.1 micron, and most likely <~0.01 micron). We attribute the dust grains to have been formed in a dense cooling shell as a result of a strong SN-circumstellar media (CSM) interaction. The dust grains occupy ~10% of the emitting volume, suggesting an inhomogeneous, clumpy structure. The average CSM density is required to be >~3 x 10^{7} cm^{-3}, corresponding to a mass loss rate of >~0.02 Msun yr^{-1} (for a mass loss wind velocity of ~100 km s^{-1}). This strongly supports a scenario that SN 2010jl and probably other luminous SNe IIn are powered by strong interactions within very dense CSM, perhaps created by Luminous Blue Variable (LBV)-like eruptions within the last century before the explosion.
    The Astrophysical Journal 08/2013; 776(1). DOI:10.1088/0004-637X/776/1/5 · 6.28 Impact Factor
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    ABSTRACT: Nonlinear transmission spectroscopy was performed on a doped Ge:Ga semiconductor using intense THz pulses with different cycle numbers. When single-cycle pulses were used, non-perturbative phenomena, such as the ionization of shallow impurities, competed with the conventional coherent transition, whereas the coherent transition was dominant when multi-cycle pulses were used.
    New Journal of Physics 06/2013; 15(6):065012. DOI:10.1088/1367-2630/15/6/065012 · 3.67 Impact Factor
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    ABSTRACT: To control the carrier envelope phase (CEP) is very important when we employ a few cycle electro-magnetic pulses for nonlinear phenomena such as higher-order harmonic generation [1], strong-field ionization and dissociation[2], and population transfer between two bound states [3]. Hence it should also be essential for nonlinear spectroscopy in the terahertz (THz) frequency region. Recently, the generation of extremely intense monocycle THz pulses has been established with the nonresonant optical rectification process and various THz nonlinear spectroscopies have been demonstrated [4]. The CEP of such THz pulses is originally locked in principle. However, to change the CEP arbitrarily has been impossible so far. To overcome the task, we focused our attention on the novel property of a series of parallel plate waveguides. For the TE mode in the waveguide [5], the phase velocity vp is larger than the light velocity c in the vacuum while the group velocity vg is smaller. If the chirp caused by the group velocity dispersion is negligible, the CEP of the THz pulse is changed during its propagation in the dispersive medium.The schematic of the dispersive medium, which we used for the CEP control is shown in Fig. 1 (a). It consists of tens of 50×10×0.1mm3 stainless plates aligned with an equal spacing of 3, 2, and 1mm. The cut-off frequencies of the media are c/2g =0.05, 0.07, and 0.15 THz, respectively. Figure 1(b) shows the temporal electric-field profile of the transmitted THz pulse with the polarization parallel (TE mode; bold) and perpendicular (TEM mode; thin) to the steel plates. In the case of g=1mm, the profile for the TE mode pulse is chirped due to the group velocity dispersion. The chirp is negligible for g≥2mm and we can clearly see the carrier phase of the pulse slightly shifts towards earlier time keeping the envelope phase stable. This means that the CEP of the THz pulse is obviously modulated; the shifted value- is ~π/2 CEP for g=2mm. Figure 1 (c) shows the complex transmission coefficient of these medium, and the transmissivity of this optics is above 50%. Such arbitrary-CEP-controlled THz pulses will give us a new field of phase-sensitive THz nonlinear spectroscopy.
    The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: We present a spatially resolved imaging analysis of a three-component gravitationally lensed quasar at z = 3.91, APM 08279+5255, in the L'- and M'-bands, and a narrow band centered at 3.05 μm using the 188-element adaptive optics system on the Subaru Telescope. The third, faintest quasar image, component C, has been clearly resolved in all of these bands for the first time. All of the three components are point sources in all three bands. No new component, neither a fourth quasar image nor a lens galaxy, was discovered. The observed bands correspond to the long-wavelength end of the optical power-law continuum of the source quasar in its rest frame, and are little contaminated by strong emission lines like Hα. The measured flux ratio of components C to B is shown to be constant in all of the observed bands, and its achromatic nature agrees well with preceding work done at short near-infrared wavelengths one decade ago. On the other hand, the flux ratio of components A to B shows an increase from that of past measurements. This could be ascribed to a microlensing event.
    Publications- Astronomical Society of Japan 02/2013; DOI:10.1093/pasj/65.1.9 · 2.01 Impact Factor
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    ABSTRACT: We investigated nonlinear THz response of a doped semiconductor using intense THz pulses with different cycle-number. Coherent transitions between impurity levels were observed using few-cycle pulses, while ionization of impunities was driven by monocycle pulses.
    Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2013 Conference on; 01/2013
  • N. Mukai, M. Nagai, Y. Minowa, M. Ashida
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    ABSTRACT: We propose a simple THz wave plate based on the structured parallel metal plates. The fast and slow propagation properties for TE and TM waveguide modes bring in the controllable birefringence in wide frequency region. Using this optics, we experimentally obtained intense single-cycle THz pulse with the circular polarization.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on; 01/2013
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    ABSTRACT: We present the near-infrared images and spectra of four silhouette disks in the Orion Nebula Cluster (ONC; M42) and M43 using the Subaru Adaptive Optics system. While d053-717 and d141-1952 show no water ice feature at 3.1 micron, a moderately deep (tau~0.7) water ice absorption is detected toward d132-1832 and d216-0939. Taking into account the water ice so far detected in the silhouette disks, the critical inclination angle to produce a water ice absorption feature is confirmed to be 65-75deg. As for d216-0939, the crystallized water ice profile is exactly the same as in the previous observations taken 3.63 years ago. If the water ice material is located at 30AU, then the observations suggest it is uniform at a scale of about 3.5AU.
    The Astronomical Journal 10/2012; 144(6). DOI:10.1088/0004-6256/144/6/175 · 4.97 Impact Factor
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    ABSTRACT: We performed multiband deep imaging of the field around GRB 050730 to identify the host galaxies of intervening absorbers, which consist of a damped Lyα absorption (DLA) system at z abs = 3.564, a sub-DLA system at z abs = 3.022, and strong Mg II absorption systems at z abs = 1.773 and 2.253. Our observations were performed after the gamma-ray burst afterglow had disappeared. Thus, our imaging survey has a higher sensitivity to the host galaxies of the intervening absorbers than the normal imaging surveys in the direction of QSOs, for which the QSO glare tends to hide the foreground galaxies. In this deep imaging survey, we could not detect any unambiguous candidates for the host galaxies of the intervening absorbers. Using the 3σ upper limit of the flux in the optical to mid-infrared observing bands, which corresponds to the UV to optical bands in the rest frame of the intervening absorbers, we constrained the star formation rates and stellar masses of the hosts. We estimated the star formation rates for the intervening absorbers to be 2.5 M ☉ yr–1 for z > 3 DLAs and 1.0 M ☉ yr–1 for z ~ 2 Mg II systems. Their stellar masses are estimated to be several times 109M ☉ or smaller for all intervening galaxies. These properties are comparable to dwarf galaxies, rather than the massive star-forming galaxies commonly seen in the z > 2 galaxy surveys based on emission-line selection or color selection.
    The Astronomical Journal 07/2012; 144(3):74. DOI:10.1088/0004-6256/144/3/74 · 4.97 Impact Factor

Publication Stats

508 Citations
165.21 Total Impact Points

Institutions

  • 2014
    • Hokkaido University
      • Department of Cosmosciences
      Sapporo, Hokkaidō, Japan
    • The Graduate University for Advanced Studies
      • Department of Astronomical Science
      Миура, Kanagawa, Japan
  • 2012–2014
    • Osaka University
      • Graduate School of Engineering Sciences
      Suika, Ōsaka, Japan
  • 2008–2011
    • Kyoto University
      • Department of Physics II
      Kioto, Kyōto, Japan
  • 2002–2010
    • National Astronomical Observatory of Japan
      • Division of Optical and Infrared Astronomy
      Edo, Tōkyō, Japan
  • 2003–2007
    • The University of Tokyo
      • Department of Astronomy
      Edo, Tōkyō, Japan