Publications

@article{OEA_RefItem:1,

title = {Recent improvement of silicon absorption in opto-electric devices},

author = {Takashi Yatsui},

doi = {10.29026/oea.2019.190023},

year  = {2019},

date = {2019-10-01},

urldate = {2019-10-01},

journal = {Opto-Electronic Advances},

volume = {2},

number = {10},

pages = {190023},

publisher = {OEA},

abstract = {Silicon dominates the contemporary electronic industry. However, being an indirect band-gap material, it is a poor absorber of light, which decreases the efficiency of Si-based photodetectors and photovoltaic devices. This review highlights recent studies performed towards improving the optical absorption of Si. A summary of recent theoretical approaches based on the first principle calculation has been provided. It is followed by an overview of recent experimental approaches including scattering, plasmon, hot electron, and near-field effects. The article concludes with a perspective on the future research direction of Si-based photodetectors and photovoltaic devices.},

note = {review article, selected as cover story},

keywords = {Direct wave-vector excitation, First, First principle calculation, Indirect band gap, Near-field effect, Plasmon, Review, Si},

pubstate = {published},

tppubtype = {article}

}

@article{2014Matsui,

title = {Coupling of Er light emissions to plasmon modes on In2O3: Sn nanoparticle sheets in the near-infrared range},

author = {Hiroaki Matsui and Wasanthamala Badalawa and Takayuki Hasebe and Shinya Furuta and Wataru Nomura and Takashi Yatsui and Motoichi Ohtsu and Hitoshi Tabata},

doi = {10.1063/1.4892004},

year  = {2014},

date = {2014-07-01},

journal = {Applied Physics Letters},

volume = {105},

number = {4},

pages = {041903},

abstract = {Near-infrared Er photoluminescence (PL) is markedly modified using a plasmonic In2O3: Sn nanoparticle (NP) sheet. Modeling and optical measurements reveal the presence of different electric fields (E-field) in the NP sheet. The local E-field excited at the interface between the NP sheet and Er-emitting layer of ZnO contributes significantly towards the spectral modifications of Er PL due to matching with the photon energy of Er PL. We also determine the critical temperature for Er PL modifications, which is related to the energy transfer efficiency between Er transition dipoles in ZnO and the plasmon modes on the NP sheet.},

keywords = {In2O3: Sn, Plasmon, ZnO},

pubstate = {published},

tppubtype = {article}

}

@article{Matsui:11,

title = {Optical dynamics of energy-transfer from a CdZnO quantum well to a proximal Ag nanostructure},

author = {Hiroaki Matsui and Wataru Nomura and Takashi Yatsui and Motoichi Ohtsu and Hitoshi Tabata},

doi = {10.1364/OL.36.003735},

year  = {2011},

date = {2011-10-01},

journal = {Optics Letters},

volume = {36},

number = {19},

pages = {3735--3737},

publisher = {OSA},

abstract = {We studied photoluminescence (PL) and energy-transfer dynamics in a hybrid structure comprising a Cd0.08Zn0.92O quantum well (QW) and an Ag nanostructure. The observed PL quenching was dependent on the electronic states in the QW. Quenching occurred at low temperature where excited carriers recombined radiatively because of excitonic localization, which disappeared with increasing temperature due to delocalization of excitons. Furthermore, nanostructured Ag surfaces produced local surface plasmon (LSP) absorption that was resonant with the PL peak energy of the QW emission. These results indicate that the recombination energy of excitons transfers nonradiatively to induce LSP excitation, which was revealed using time-resolved PL measurements.},

keywords = {Energy-transfer, Plasmon, QW},

pubstate = {published},

tppubtype = {article}

}

@article{2006nomuraAPB,

title = {Efficient optical near-field energy transfer along an Au nanodot coupler with size-dependent resonance},

author = {Wataru Nomura and Motoichi Ohtsu and Takashi Yatsui},

doi = {10.1007/s00340-006-2165-6},

year  = {2006},

date = {2006-07-01},

journal = {Applied Physics B},

volume = {84},

number = {1-2},

pages = {257-259},

publisher = {Springer Nature},

abstract = {We confirmed that the light intensity (wavelength of 785 nm) scattered from an isolated hemispherical Au nanoparticle was resonantly enhanced at a diameter of 200 nm and a height of 50 nm, as observed experimentally using a collection-mode near-field optical microscope. The experimental results agreed with the calculated results using Mie's theory. Furthermore, we observed resonant energy transfer of the optical near-field energy along a chain of Au nanoparticles. The magnitude of the transferred energy increased resonantly at the size of resonant light scattering for an isolated Au nanoparticle (200 nm diameter with 240 nm center-to-center separation).},

keywords = {Plasmon},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/nl051898z,

title = {Self-Assembly of Size- and Position-Controlled Ultralong Nanodot Chains using Near-Field Optical Desorption},

author = {Takashi Yatsui and Wataru Nomura and Motoichi Ohtsu},

doi = {10.1021/nl051898z},

year  = {2005},

date = {2005-12-01},

journal = {Nano Letters},

volume = {5},

number = {12},

pages = {2548-2551},

abstract = {We report the self-assembly of a size- and position-controlled ultralong nanodot chain using a novel effect of near-field optical desorption. A sub-100-nm dot chain with a deviation of 5 nm forms at a size based on plasmon resonance, depending on the photon energy; the resulting structure forms a high-transmission-efficiency nanoscale waveguide. Using this method with simple lithographically patterned substrates allows one to increase the throughput of the production of nanoscale structures dramatically at all scales.},

note = {PMID: 16351213},

keywords = {First, Nanophotonic fabrication, Plasmon, Selected, Self-assembly},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.1920419,

title = {Nanodot coupler with a surface plasmon polariton condenser for optical far/near-field conversion},

author = {Wataru Nomura and Motoichi Ohtsu and Takashi Yatsui},

doi = {10.1063/1.1920419},

year  = {2005},

date = {2005-05-01},

journal = {Applied Physics Letters},

volume = {86},

number = {18},

pages = {181108},

abstract = {To transmit an optical signal to a nanophotonic device, a nanodot coupler was fabricated from a linear array of closely spaced metallic nanoparticles. To increase the optical far- to near-field conversion efficiency for transmission, a surface plasmon polariton (SPP) condenser was also fabricated from hemispherical metallic nanoparticles so that it worked as a “phased array”. The SPP was focused with a spot size as small as 400 nm at λ=785nm. When the focused SPP was incident into the nanodot coupler, its transmission length through the nanodot coupler was confirmed to be 4.0 μm, which is three times longer than that of a metallic core waveguide owing to the efficient near-field coupling between the localized surface plasmon of neighboring nanoparticles. Furthermore, the transmission length through a zigzag-shaped nanodot coupler was as long as that through a linear one.},

keywords = {Plasmon, Selected},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.1465520,

title = {Metallized pyramidal silicon probe with extremely high throughput and resolution capability for optical near-field technology},

author = {Takashi Yatsui and Kazutaka Itsumi and Motonobu Kourogi and Motoichi Ohtsu},

doi = {10.1063/1.1465520},

year  = {2002},

date = {2002-04-01},

journal = {Applied Physics Letters},

volume = {80},

number = {13},

pages = {2257-2259},

abstract = {An optical near-field probe with extremely high throughput and resolution capability was fabricated with a metallized pyramidal silicon structure. Using a finite-difference time-domain method, we found the tip parameters that are required for localized surface plasmon resonance at the probe tip. The optical near-field energy distribution on the metallized pyramidal silicon probe was observed by scanning a fiber probe that had an aperture diameter of 50 nm. The spatial distribution profile observed was in good agreement with the numerical results. The throughput and spot size were determined to be 2.3% and 85 nm, respectively.},

keywords = {First, near-field optical recording, Plasmon},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.1428405,

title = {Plasmon waveguide for optical far/near-field conversion},

author = {Takashi Yatsui and Motonobu Kourogi and Motoichi Ohtsu},

doi = {10.1063/1.1428405},

year  = {2001},

date = {2001-12-01},

journal = {Applied Physics Letters},

volume = {79},

number = {27},

pages = {4583-4585},

abstract = {A plasmon waveguide was designed and fabricated using a metal-coated silicon wedge structure that converts propagating far-field light to the near field. Illumination (λ=830 nm) of the waveguide (plateau width 150 nm) caused transverse magnetic plasmon-mode excitation. Use of a near-field microscope allowed us to determine its beam width and propagation length as 150 nm and 2.5 μm, respectively.},

keywords = {First, Plasmon, Selected},

pubstate = {published},

tppubtype = {article}

}

@article{Yatsui:00,

title = {High-density-speed optical near-field recording--reading with a pyramidal silicon probe on a contact slider},

author = {Takashi Yatsui and Motonobu Kourogi and Kazuo Tsutsui and Motoichi Ohtsu and Jun-ichi Takahashi},

doi = {10.1364/OL.25.001279},

year  = {2000},

date = {2000-09-01},

journal = {Optics Letters},

volume = {25},

number = {17},

pages = {1279-1281},

publisher = {OSA},

abstract = {We demonstrate high-density-speed phase-change recording-reading by use of a pyramidal silicon structure. The contact slider, which has a pyramidal silicon probe array with height dispersion of less than 10 nm, is fabricated by use of a silicon-on-insulator wafer. By illumination with a laser beam λ=830 nm of one element of the probe array, we find the shortest phase-change mark length and the carrier-to-noise ratio to be 110 nm and 10 dB, respectively, corresponding to a data transmission rate of 2.0 MHz. This rate can be increased to 200 MHz by use of all elements of the probe array.},

keywords = {First, near-field optical recording, Plasmon},

pubstate = {published},

tppubtype = {article}

}

@article{1998matsumoto,

title = {Fabrication of a Near-Field Optical Fiber Probe with a Nanometric Metallized Protrusion},

author = {Takuya Matsumoto and Tutomu Ichimura and Takashi Yatsui and Motonobu Kourogi and Toshiharu Saiki and Motoichi Ohtsu},

doi = {10.1007/s10043-998-0369-1},

year  = {1998},

date = {1998-12-01},

journal = {Optical Review},

volume = {5},

number = {6},

pages = {369-373},

publisher = {Springer Nature},

abstract = {We have developed a novel probe with a nanometric metallized protrusion extending through a subwavelength aperture to increase optical near-field excitation and collection efficiencies. The apex diameter of the fabricated metallized protrusion was 35 nm. The Intensity distribution of the optical near-field at the apex of the probe was measured by scanning another probe across the apex, and it was observed that strong optical near-field was generated at the apex of the metallized protrusion. The width of the intensity distribution was 150 nm including instrumental resolution. Probes with spherical and ellipsoidal metallized protrusion were also fabricated, by which enhancement of the optical near-field is expected due to localized plasmon excitation.},

keywords = {Plasmon},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.122387,

title = {Increasing throughput of a near-field optical fiber probe over 1000 times by the use of a triple-tapered structure},

author = {Takashi Yatsui and Motonobu Kourogi and Motoichi Ohtsu},

doi = {10.1063/1.122387},

year  = {1998},

date = {1998-10-01},

journal = {Applied Physics Letters},

volume = {73},

number = {15},

pages = {2090-2092},

abstract = {We fabricated a new probe with extremely high throughput introducing a triple-tapered structure to reduce the loss in a tapered core, to focus the light, and to excite effectively the HE11 mode. A focused ion beam and selective chemical etching were used for fabrication. Over a 1000-fold increase in the throughput of the triple-tapered probe with the aperture diameter D<100 nm was realized in comparison with the conventional single-tapered probe. Furthermore, due to the third taper with a small cone angle, the localized optical near field on the triple-tapered apertured probe with D=60 nm has been confirmed.},

keywords = {First, Plasmon, Selected},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.119390,

title = {Highly efficient excitation of optical near-field on an apertured fiber probe with an asymmetric structure},

author = {Takashi Yatsui and Motonobu Kourogi and Motoichi Ohtsu},

doi = {10.1063/1.119390},

year  = {1997},

date = {1997-09-01},

journal = {Applied Physics Letters},

volume = {71},

number = {13},

pages = {1756-1758},

abstract = {We propose and demonstrate a novel method to enhance the near-field optical intensity on the apertured probe with its foot removed asymmetrically by using a focused ion beam. The spatial distribution of the near-field optical intensity on the asymmetric probe was observed by scanning another sharpened symmetric probe over the aperture. The observed spatial distribution profile was in good agreement with a numerical result corresponding to the HE11 mode. Furthermore, compared with the symmetric apertured probe, a 10 times enhancement of the near-field optical intensity on the asymmetric apertured probe was observed.},

keywords = {First, Plasmon},

pubstate = {published},

tppubtype = {article}

}