Continuous tuning of an electrically tunable external-cavity semiconductor laser

We propose and demonstrate a novel approach to achieving rapid and phase-coherent continuous broadband tuning of a single-mode external-cavity semiconductor laser. Two internal acousto-optic devices control the angle of incident light on a diffraction grating and the effective round-trip phase electronically. Although the present implementation derives the phase from a long delay line and is not yet mode-hop free, the new approach lends itself to fully electronic control.     

Vector-meson-dominance model for radiative decays involving light scalar mesons

We study a vector-dominance model which predicts quite a large number of currently interesting decay amplitudes of the types S-->gammagamma, V-->Sgamma, and S-->Vgamma, where S and V denote scalar and vector mesons, in terms of three parameters. As an application, the model makes it easy to study in detail a recent proposal to boost the ratio Gamma(phi-->f(0)gamma)/Gamma(phi-->a(0)(0)gamma) by including the isospin violating a(0)(0)-f(0) mixing. However, we find that this effect is actually small in our model.     

Second-harmonic generation in a near-field optical-fiber probe

Second-harmonic generation (SHG) in a near-field optical-fiber probe was observed. The tip of the probe consists of a triple-tapered fiber with an aluminum coating. For a fiber probe with an aperture size of 100 nm, the SHG conversion factor was 2.0 x 10(-11)cm(2)/W , which is as large as that of a 5-mm KDP crystal. In a probe-to-probe experiment, we demonstrated that SHG took place at the aluminum coating on the fiber probe.     

A stochastic modeling of morphology formation by optical near-field processes

We previously reported (S. Yukutake et al. in Appl. Phys. B 99:415, 2010) that by depositing Ag particles on the electrode of a photovoltaic device composed of poly(3-hexylthiophene) (P3HT) and ZnO under light illumination (wavelength λ=660 nm) while reversely biasing the P3HT/ZnO p–n junction, a unique granular Ag film was formed. The resultant device generated a photocurrent at wavelengths as long as 670 nm, which is longer than the long-wavelength cutoff λ _c (=570 nm) of P3HT. Such an effect originates from a phonon-assisted process induced by an optical near field. In this paper, we analyze the morphological character of the Ag clusters and build a stochastic model in order to understand the principles behind the self-organized pattern formation process. The modeling includes the geometrical character of the material, its associated optical near fields, and the materials that flow in and out of the system. The model demonstrates behavior consistent with that observed in the experiment. We can see these phenomena as a new kind of self-organized criticality taking account of near-field effects, which will provide an insight into the analysis and design of future nanophotonic devices.     

Bulk crystal SiC blue LED with p–n homojunction structure fabricated by dressed-photon-phonon–assisted annealing

To fabricate a high-efficiency light emitting diode using indirect-transition-type bulk crystal SiC having a p–n homojunction structure, annealing was performed using stimulated emission via dressed photons generated at the inhomogeneous domain boundaries of Al dopant sites. This device emitted electroluminescence (EL) due to a two-step transition process via dressed-photon–phonons generated at the inhomogeneous domain boundaries of the Al dopant sites. The EL emission peak wavelength was 480–515 nm when the device was driven by a direct current and 390 nm when driven by a pulsed current. The external quantum efficiency of the EL emission was 1 %, and the internal quantum efficiency was as high as 10 %.     

Fabrication of a bulk silicon p–n homojunction-structured light-emitting diode showing visible electroluminescence at room temperature

We have developed a novel dressed-photon-assisted annealing process, in which the distribution of dopant (boron) domains is modified in a self-organized manner based on the absorption of light having a photon energy higher than the band gap and subsequent stimulated emission. Using this process, we were able to fabricate a bulk silicon p–n homojunction-structured light-emitting diode that showed electroluminescence emission in the visible region at room temperature. A broadband spectrum with three emission peaks at 400 nm, 590 nm, and 620 nm was clearly observed.     

Construction of a functional IgG-binding luciferase fusion protein for the rapid detection of specific bacterial strains

A fusion protein consisting of two IgG-binding domains of streptococcal protein G and firefly luciferase was constructed, and a simple and specific bioluminescent immunodetection system for bacterial strains was developed.     

2-Acyl-tetrahydroisoquinoline-3-carboxylic acids: lead compounds with triple actions, peroxisome proliferator-activated receptor α/γ agonist and protein-tyrosine phosphatase 1B inhibitory activities

2-Acyl-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and biologically evaluated. (S)-2-(2,4-Hexadienoyl)-7-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14) showed peroxisome proliferator-activated receptor γ (PPARγ) and PPARα agonist activities and protein-tyrosine phosphatase 1B (PTP-1B) inhibitory activities. PPARγ agonist activity of 14 was comparable to that of rosiglitazone, and PTP-1B inhibitory activity was about 10-fold weaker than that of ertiprotafib, a PTP-1B inhibitor. Compound 14 showed high oral absorption in rats and potent hypoglycemic effects in KK-A(y) mice. In conclusion, 14 would be an excellent lead compound for a new type of anti-diabetic drug with triple actions.