Publications

@article{SHvirus,

title = {Virus Detection using Second Harmonics of Magnetic Nanoparticles},

author = {Ryuichi Hirota and Toru Murayama and Ryota Katsumi and Tokuhisa Kawawaki and Shin Yabukami and Ryuji Igarashi and Yuichi Negishi and Moriaki Kusakabe and Masaki Sekino and Takashi Yatsui and Akihiro Kuwahata},

doi = {10.1002/tee.23613},

year  = {2022},

date = {2022-04-12},

urldate = {2022-04-12},

journal = {IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING},

volume = {17},

issue = {8},

pages = {1228-1230},

abstract = {Virus detection methods based on the nonlinear magnetic response of magnetic nanoparticles have been investigated, and magnetic detection methods using the third harmonic have been widely applied on account of their high sensitivity, short measurement-time, and low cost. In this letter, we propose a virus detection method using the second harmonics to improve the signal intensity. We find that the signal to noise ratio of the second harmonic is approximately three times higher than that of the third harmonic. A comparison of the ratio of the second harmonic to the fourth harmonic (R24) and the ratio of the third harmonic to the fifth harmonic (R35) shows that R24 is more sensitive to identifying changes in virus concentration. Our proposed method has the potential to be utilized for rapid screening on virus detection.},

keywords = {SHG, Virus Detection},

pubstate = {published},

tppubtype = {article}

}

@article{ag21,

title = {Synthesis of silver nanostructure on gold nanoparticle using near field assisted second harmonic generation},

author = {Takashi Yatsui and Felix Brandenburg and Benjamin Leuschel and Olivier Soppera},

doi = {10.1038/s41598-021-84944-w},

year  = {2021},

date = {2021-03-11},

urldate = {2021-03-11},

journal = {Scientific Reports},

volume = {11},

pages = {5642},

abstract = {By using gold (Au) nanoparticles (NPs) as an optical near-field source under far-field illumination in combination with a silver (Ag) ion solution containing a photoinitiator, we coated Ag on Au NPs using a near-field (NF)-assisted process. We evaluated the change in the size of the NPs using transmission electron microscopy. Evaluation of the synthesized Ag volume over illumination power confirmed the squared power dependence of the NP volume with illumination using 808 nm light, i.e., a wavelength longer than the absorption edge wavelength of the photoinitiator molecules. The rate of volume increase was much lower than the plasmonic field enhancement effect. Therefore, the squared power dependency of the volume increase using a wavelength longer than the absorption edge wavelength originated from NF-assisted second-harmonic generation and the resulting excitation.},

keywords = {First, Nanophotonic fabrication, Near-field effect, SHG},

pubstate = {published},

tppubtype = {article}

}

@article{YATSUI2017166,

title = {Nano-scale chemical reactions based on non-uniform optical near-fields and their applications},

author = {Takashi Yatsui and Maiku Yamaguchi and Katsuyuki Nobusada},

doi = {10.1016/j.pquantelec.2017.06.001},

issn = {0079-6727},

year  = {2017},

date = {2017-09-01},

journal = {Progress in Quantum Electronics},

volume = {55},

pages = {166 - 194},

abstract = {Interaction between light and materials is essential in the physics underlying all optical devices, including light emitting devices such as light emitting diodes and lasers, photo-voltaic devices, and photo-synthesis systems. The demand for higher light utilization efficiency is becoming increasingly important for advanced optical devices. This is because, when feature size is smaller than the incident light wavelength, photons cannot couple with devices efficiently. In this paper, we review recent progress regarding a unique phenomenon at the nano scale and its applications. First, we summarize the development of light–matter interactions at the nano-scale. Second, we review recent theoretical works focusing on optical near fields in which unique phenomena arise from non-uniform optical fields. We then review several recent developments based on the near-field effect, including artificial photosynthesis and near-field etching for realization of angstrom-scale fattened surfaces. Finally, we discuss the future outlook for these technologies.},

note = {review article},

keywords = {Artificial photosynthesis, First, Near-field etching, Non-uniform optical near field, Photodissociation path with two-step excitation, Review, Selected, SHG},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.92.043809,

title = {Nonlinear optical response induced by a second-harmonic electric-field component concomitant with optical near-field excitation},

author = {Maiku Yamaguchi and Katsuyuki Nobusada and Takashi Yatsui},

doi = {10.1103/PhysRevA.92.043809},

year  = {2015},

date = {2015-10-01},

journal = {Phys. Rev. A},

volume = {92},

number = {4},

pages = {043809},

publisher = {American Physical Society},

abstract = {Electron dynamics excited by an optical near field (ONF) in a two-dimensional quantum dot model was investigated by solving a time-dependent Schrödinger equation. It was found that the ONF excitation of the electron caused two characteristic phenomena: a two-photon absorption and an induction of a magnetic dipole moment with a strong third-harmonic component. By analyzing the interaction dynamics of the ONF and the electron, we explained that the physical mechanism underlying these phenomena was the second-harmonic electric-field component concomitant with the near-field excitation originating from the nonuniformity of the ONF. Despite a y-polarized ONF source, the second-harmonic component of an 

x-polarized electric field was inherently generated. The effect of the second-harmonic electric-field component is not due to usual second-order nonlinear response but appears only when we explicitly consider the electron dynamics interacting with the ONF beyond the conventional optical response assuming the dipole approximation.},

keywords = {Non-uniform optical near field, Selected, SHG},

pubstate = {published},

tppubtype = {article}

}

@article{2015SHG,

title = {Two-photon absorption induced by electric field gradient of optical near-field and its application to photolithography},

author = {Maiku Yamaguchi and Katsuyuki Nobusada and Tadashi Kawazoe and Takashi Yatsui},

doi = {10.1063/1.4921005},

year  = {2015},

date = {2015-05-01},

urldate = {2015-05-01},

journal = {Applied Physics Letters},

volume = {106},

number = {19},

pages = {191103},

abstract = {An electric field gradient is an inherent property of the optical near-field (ONF). We investigated its effect on electron excitation in a quantum dot via model calculations combining a density matrix formalism and a classical Lorentz model. The electric field gradient of the ONF was found to cause two-photon absorption by an unusual mechanism. Furthermore, the absorption exhibits a nonmonotonic dependence on the spatial arrangement of the nanosystem, completely different from that of conventional two-photon absorption induced by an intense electric field. The present two-photon absorption process was verified in a previous experimental observation by reinterpreting the results of ONF photolithography.},

keywords = {Nanophotonic fabrication, Non-uniform optical near field, SHG},

pubstate = {published},

tppubtype = {article}

}

@article{2012NatPhoton,

title = {Observing the localization of light in space and time by ultrafast second-harmonic microscopy},

author = {Manfred Mascheck and Stephen Schmidt and Martin Silies and Takashi Yatsui and Kokoro Kitamura and Motoichi Ohtsu and David Leipold and Erich Runge and Christoph Lienau},

url = {https://www.altmetric.com/details/698801},

doi = {10.1038/nphoton.2012.69},

year  = {2012},

date = {2012-05-01},

journal = {Nature Photonics},

volume = {6},

number = {5},

pages = {293-298},

publisher = {Springer Nature},

abstract = {Multiple coherent scattering and the constructive interference of certain scattering paths form the common scheme of several remarkable localization phenomena of classical and quantum waves in randomly disordered media. Prominent examples are electron transport in disordered conductors, the localization of excitons in semiconductor nanostructures, surface plasmon polaritons at rough metallic films or light in disordered dielectrics and amplifying media. However, direct observation of the fundamental spatiotemporal dynamics of the localization process remains challenging. This holds true, in particular, for the localization of light occurring on exceedingly short femtosecond timescales and nanometre length scales. Here, we combine second harmonic microscopy with few-cycle time resolution to probe the spatiotemporal localization of light waves in a random dielectric medium. We find lifetimes of the photon modes of several femtoseconds and a broad distribution of the local optical density of states, revealing central hallmarks of the localization of light.},

keywords = {Near-field effect, Selected, SHG},

pubstate = {published},

tppubtype = {article}

}

@article{Schmidt:10,

title = {Distinguishing between ultrafast optical harmonic generation and multi-photon-induced luminescence from ZnO thin films by frequency-resolved interferometric autocorrelation microscopy},

author = {Stephen Schmidt and Manfred Mascheck and Martin Silies and Takashi Yatsui and Kokoro Kitamura and Motoichi Ohtsu and Christoph Lienau},

doi = {10.1364/OE.18.025016},

year  = {2010},

date = {2010-11-01},

journal = {Optics Express},

volume = {18},

number = {24},

pages = {25016--25028},

publisher = {OSA},

abstract = {The nonlinear optical properties of thin ZnO film are studied using interferometric autocorrelation (IFRAC) microscopy. Ultrafast, below-bandgap excitation with 6-fs laser pulses at 800 nm focused to a spot size of 1 textmum results in two emission bands in the blue and blue-green spectral region with distinctly different coherence properties. We show that an analysis of the wavelength-dependence of the interference fringes in the IFRAC signal allows for an unambiguous assignment of these bands as coherent second harmonic emission and incoherent, multiphoton-induced photoluminescence, respectively. More generally our analysis shows that IFRAC allows for a complete characterization of the coherence properties of the nonlinear optical emission from nanostructures in a single-beam experiment. Since this technique combines a very high temporal and spatial resolution we anticipate broad applications in nonlinear nano-optics.},

keywords = {SHG, ZnO},

pubstate = {published},

tppubtype = {article}

}