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Yuta Inose

Bio: Yuta Inose is an academic researcher from Sophia University. The author has contributed to research in topics: Anderson localization & Photoluminescence. The author has an hindex of 6, co-authored 20 publications receiving 155 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors reported observations of random laser action in self-organized GaN nanocolumns and measured three samples with different filling fractions and investigated the dependence of the lasing property on the random configuration of Nanocolumn.
Abstract: We report observations of random laser action in self-organized GaN nanocolumns. We have measured three samples with different filling fractions and investigated the dependence of the lasing property on the random configuration of nanocolumns. Numerical calculations based on a finite-difference time-domain method have also been performed and the comparison with the experimental results shows a clear relationship between the strength of light localization and the occurrence of random laser action.

82 citations

Journal ArticleDOI
TL;DR: In this paper, the spectral change and reduction of photoluminescence (PL) efficiency are explained by filling of the localized states and population into the extended states around the mobility edge density.
Abstract: We have measured and analyzed the carrier-density dependence of photoluminescence (PL) spectra and the PL efficiency of InGaN/GaN multiple quantum wells in nanocolumns and in a thin film over a wide excitation range. The localized states parameters, such as the tailing parameter, density and size of the localized states, and the mobility edge density are estimated. The spectral change and reduction of PL efficiency are explained by filling of the localized states and population into the extended states around the mobility edge density. We have also found that the nanocolumns have a narrower distribution of the localized states and a higher PL efficiency than those of the film sample although the In composition of the nanocolumns is higher than that of the film.

18 citations

Journal ArticleDOI
TL;DR: In this paper, the authors have simulated temporal diffusion of electromagnetic waves in a random system with a high filling fraction of the columns, using the finite-difference time-domain method.
Abstract: In the two-dimensional random system composed of a disordered array of dielectric cylindrical columns, Anderson localization of light occurs. To obtain frequency dependence of the light localization characteristics, we have simulated temporal diffusion of electromagnetic waves in such a random system adopting parameters of actual nanosized semiconductor samples with a high filling fraction of the columns, using the finite-difference time-domain method. We have investigated diffusion length, autocorrelation function of light energy density, and time variation in total energy within the system at several frequencies. We obtain universal behavior of light localization phenomenon as a function of the light localization length and system size, from which we estimate frequency dependence of the localization length. In addition, we show that the frequency dependence of the localization effect depends on the degree of wave interference due to Bragg-like diffraction, rather than on the magnitude of the light scattering cross section of a single scatterer.

15 citations

Journal ArticleDOI
TL;DR: In this article, the first near-field optical imaging of light localization in a GaN nanocolumn system was performed, using an aperture-type scanning near field optical microscope.
Abstract: The first near-field optical imaging of light localization in a GaN nanocolumn system was performed. The sample used was a randomly arranged GaN nanocolumn with high aspect ratio. We attached an InGaN single quantum well at the apex of each GaN nanocolumn as an illuminant antenna and observed luminescence from the illuminant using an aperture-type scanning near-field optical microscope. By this technique, we directly obtained optical images of luminescence and its spatial distribution for the GaN nanocolumn system. These images, along with histogram analysis, excitation wavelength dependence, and numerical calculations, offer evidence of Anderson localization of light.

14 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured photoluminescence (PL) from excitons and biexcitons in GaN nanocolumns at low temperature and found that the PL spectra depended on the diameter of the nanocolumin diameter.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors present a review of the current state of the art in the field of random distributed feedback feedback laser (RDFL) generation, and discuss existing and future applications of random fiber laser, including telecommunication and distributed long reach sensor systems.

410 citations

Journal ArticleDOI
K. H. Li1, Xianhe Liu1, Qingxiao Wang1, Songrui Zhao1, Zetian Mi1 
TL;DR: It is reported that defect-free disordered AlGaN core-shell nanowire arrays, formed directly on a Si substrate, can be used to achieve highly stable, electrically pumped lasers across the entire ultraviolet AII (UV-AII) band (∼320-340 nm) at low temperatures.
Abstract: Anderson localization of light in AlGaN–GaN nanowires is exploited to fabricate ultraviolet laser arrays with a lasing threshold of only a few tens of amperes per centimetre squared at cryogenic temperature.

264 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis.

189 citations

Journal ArticleDOI
TL;DR: Through the monolithic integration of p- GaN up and p-GaN down nanowire LED structures on the same substrate, it is demonstrated, for the first time, AC operated LEDs on a Si platform, which can operate efficiently in both polarities of applied voltage.
Abstract: The current LED lighting technology relies on the use of a driver to convert alternating current (AC) to low-voltage direct current (DC) power, a resistive p-GaN contact layer to inject positive charge carriers (holes) for blue light emission, and rare-earth doped phosphors to down-convert blue photons into green/red light, which have been identified as some of the major factors limiting the device efficiency, light quality, and cost. Here, we show that multiple-active region phosphor-free InGaN nanowire white LEDs connected through a polarization engineered tunnel junction can fundamentally address the afore-described challenges. Such a p-GaN contact-free LED offers the benefit of carrier regeneration, leading to enhanced light intensity and reduced efficiency droop. Moreover, through the monolithic integration of p-GaN up and p-GaN down nanowire LED structures on the same substrate, we have demonstrated, for the first time, AC operated LEDs on a Si platform, which can operate efficiently in both polarit...

83 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported observations of random laser action in self-organized GaN nanocolumns and measured three samples with different filling fractions and investigated the dependence of the lasing property on the random configuration of Nanocolumn.
Abstract: We report observations of random laser action in self-organized GaN nanocolumns. We have measured three samples with different filling fractions and investigated the dependence of the lasing property on the random configuration of nanocolumns. Numerical calculations based on a finite-difference time-domain method have also been performed and the comparison with the experimental results shows a clear relationship between the strength of light localization and the occurrence of random laser action.

82 citations