Specified Nonprofit Corporation Nanophotonics Engineering Organization

Bunkyō-ku, Japan

Specified Nonprofit Corporation Nanophotonics Engineering Organization

Bunkyō-ku, Japan
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Nomura W.,University of Tokyo | Nomura W.,Kyushu University | Yatsui T.,University of Tokyo | Yatsui T.,Tokyo International University | And 7 more authors.
Applied Physics A: Materials Science and Processing | Year: 2015

Dressed-photon–phonon (DPP) etching is a non-contact flattening technology that realizes ultra-flat surfaces and has been reported to achieve an arithmetic mean surface roughness, Ra, on the order of 0.1 nm in various materials, such as fused silica, plastic films, and GaN crystal. In this study, we successfully flattened the surface of a crystallized glass substrate in several seconds using laser light with a higher power density than that used in previous studies. The target substrate had an initial appearance similar to frosted glass, with an Ra of 92.5 nm. We performed DPP etching under a Cl2 atmosphere using a CW laser with a wavelength of 532 nm, a power of 8 W, and a spot diameter of 0.2 mm. After 1 s of processing, we obtained a flat surface with an Ra of 5.00 nm. This surface roughness equaled or surpassed that of a substrate flattened by conventional chemical mechanical polishing, with an Ra of 5.77 nm. Through the detailed analysis of atomic force microscopic images, we found the DPP etching resulted in the smaller standard deviation of the height difference than CMP in the smaller lateral size than 50 nm. © 2015 Springer-Verlag Berlin Heidelberg


Kawazoe T.,University of Tokyo | Kawazoe T.,Specified Nonprofit Corporation Nanophotonics Engineering Organization | Nishioka K.,University of Tokyo | Ohtsu M.,University of Tokyo | And 2 more authors.
International Journal of Metalcasting | Year: 2015

This paper reports the fabrication of a polarization- controlled infrared LED fabricated by dressedphoton- phonon (DPP)-assisted annealing of a bulk Si crystal. For the DPP-assisted annealing, linearly polarized infrared light with a wavelength of 1.342 lm was made normally incident on the top surface of the crystal. The photon energy at the peak of the emitted light spectrum of the fabricated LED was close to that of the light irradiated during the DPP-assisted annealing. A degree of polarization of as large as 0.07 was obtained. The spatial distribution of the doped B atoms in the fabricated LED was measured, and the following findings were obtained: (1) B atoms formed pairs in which the separation between the two B atoms was three times the lattice constant of the Si crystal; and (2) the B atom pairs were apt to orient along the direction perpendicular to the propagation direction and to the polarization direction of the light irradiated during the DPP-assisted annealing. Based on these findings (1) and (2), photon breeding was confirmed with respect to photon energy and spin, respectively. © Springer-Verlag Berlin Heidelberg 2015.


Tanaka H.,University of Tokyo | Kawazoe T.,University of Tokyo | Kawazoe T.,Specified Nonprofit Corporation Nanophotonics Engineering Organization | Ohtsu M.,University of Tokyo | And 4 more authors.
International Journal of Metalcasting | Year: 2015

We fabricated an optical waveguide having a high optical confinement effect using a silicon-on-insulator substrate, and we eliminated the difficulty involved with optical alignment for making laser light pass through a p-n homojunction that is transparent to infrared light. Laser light was introduced via one of the cleaved edges of the optical waveguide and was guided to the transparent p-n homojunction, and the power of the light emitted from the other edge was measured. As a result, we successfully evaluated the optical amplification properties with high precision. For light with a wavelength of 1.31 lm, we obtained a differential gain coefficient of g = 2.6 9 10-2 cm/A, a transparency current density of Jtr = 1 mA/cm2, and a saturation optical power density of Psat = 30 kW/cm2. The observation of gain saturation due to the incident optical power shows that this measurement method was suitable for evaluating the optical amplification properties. © Springer-Verlag Berlin Heidelberg 2015.


Yamaguchi M.,University of Tokyo | Kawazoe T.,University of Tokyo | Kawazoe T.,Specified Nonprofit Corporation Nanophotonics Engineering Organization | Yatsui T.,University of Tokyo | And 4 more authors.
Applied Physics A: Materials Science and Processing | Year: 2015

We developed a visible silicon light-emitting diode (Si-LED) with a lateral p–n homojunction using dressed-photon–phonon (DPP)-assisted annealing. The lateral p–n homojunction was fabricated in order to decrease the absorption loss inherent in light emission with a photon energy higher than the band-gap energy of the material. The fabricated Si-LED emitted light in the entire visible range, including the three primary colors. The light extraction efficiency of the Si-LED was estimated to be 7.8 times higher than that of a conventional LED structure with a vertical p–n homojunction. Owing to the efficient light extraction, we clearly observed two novel features in the electroluminescence (EL) spectrum: a nonlinear increase in the EL intensity with the injected forward current, and an emission peak at 2.7 eV, at which there is no singular point in the electronic structure. From these features, we concluded that the EL from the Si-LED originated from the phonon-assisted radiative recombination of carriers with much higher energy than that of the bottom of the conduction band, via DPPs. © 2015 Springer-Verlag Berlin Heidelberg


Kim J.H.,University of Tokyo | Kawazoe T.,University of Tokyo | Kawazoe T.,Specified Nonprofit Corporation Nanophotonics Engineering Organization | Ohtsu M.,University of Tokyo | And 2 more authors.
Applied Physics A: Materials Science and Processing | Year: 2015

Using the two-level two-state model, we analyzed the characteristics of enhanced electroluminescence intensity from a GaP LED fabricated by dressed-photon–phonon-assisted annealing. In this model, we utilized the fact that the adiabatic potential barrier of the electronic excited level in configuration space is lower than that of the ground level. It was confirmed by experiments that, in an actual excited level, the barrier was reduced to 0.48 eV. From this finding, it was shown that the spatial distribution of Zn atoms can be changed by means of current injection and light irradiation even at room temperature. In addition, we showed that a structure that is suitable for light emission via DPPs is formed by means of a transition between a low-barrier excited level and a high-barrier ground level, due to stimulated emission. Also, regarding the optimized conditions for maximizing the effect of DPP-assisted annealing, it was found that the optimum ratio of the number of injected electrons to the number of irradiated photons is close to 1, and this was confirmed experimentally. © 2015 Springer-Verlag Berlin Heidelberg

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