Fumio Koyama

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To investigate the role of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) type glutamate receptors in epileptic seizures, we examined the antiepileptogenic and anticonvulsant effects of YM90K [6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride], a potent and selective new AMPA receptor antagonist, in the rat(More)
We present a theoretical analysis of lasing action in photonic crystal surface-emitting lasers (PCSELs). The semiclassical laser equations for such structures are simulated with three different theoretical techniques: exact finite-difference time-domain calculations, an steady-state ab-initio laser theory and a semi-analytical coupled-mode formalism. Our(More)
We demonstrate an electrically pumped high contrast grating (HCG) VCSEL operating at 1550 nm incorporating a proton implant-defined aperture. Output powers of >1 mW are obtained at room temperature under continuous wave operation. Devices operate continuous wave at temperatures exceeding 60° C. The novel device design, which is grown in a single epitaxy(More)
We propose a novel design for multi-wavelength arrays of vertical cavity surface-emitting lasers (VCSELs) using high-contrast gratings (HCGs) as top mirrors. A range of VCSEL cavity wavelengths in excess of 100 nm is predicted by modifying only the period and duty-cycle of the high-contrast gratings, while leaving the epitaxial layer thickness unchanged.(More)
We introduce a compact submicron structure consisting of multiple optical microcavities at both the entrance and exit sides of a subwavelength plasmonic slit filled with an absorbing material. We show that such microcavity structures at the entrance side of the slit can greatly enhance the coupling of the incident light into the slit, by improving the(More)
We use finite-difference time-domain (FDTD) simulations to demonstrate enhanced infrared absorption in a photodetector covered with a microstructured metal film consisting of a metal-plasmon grating collec-tor/concentrator and sub-wavelength detector well; for circular gratings we use radial FDTD, and for linear gratings we use two-dimensional FDTD. We(More)
—A tunable bandpass filter is constructed using pat-terned mirrors and a diffraction grating to serve as an optical equalizer. The frequency response of an intensity-modulated light source can be tailored by the passband profile of the equalizer to achieve a larger 3-dB bandwidth. We demonstrate that the 3-dB bandwidth of two LiNO 3 modulators is increased(More)
We report a high speed 8x8 optical phased array using tunable 1550 nm all-pass filters with ultrathin high contrast gratings (HCGs) as the microelectromechanical-actuated top reflectors. The all-pass filter design enables a highly efficient phase tuning (1.7 π) with a small actuation voltage (10 V) and actuation displacement of the HCG (50 nm). The(More)