Search

Hideaki Okawada, Yuta Saito, Shigehiro Iwabuchi, Shotaro Kosuge, Haruo Takahashi, Hidetoshi Onda, Masahiro Kito Department of Ophthalmology, Showa University, Tokyo, Japan Purpose: Vascular endothelial growth factor (VEGF) plays an important role in branch retinal vein occlusion (BRVO) with cystoid macular edema (CME). Monitoring changes in VEGF is crucial for evaluating treatment but requires vitreous or aqueous humor sampling, which hampers its clinical application. We investigated the correlation between VEGF and protein concentration in the aqueous humor (flare) and whether this could be used to monitor treatment-related VEGF changes. Design: This retrospective observational study involved 19 previously untreated patients with BRVO. Aqueous humor was obtained, and intravitreal ranibizumab (IVR) injection was administered to these patients. The correlation between VEGF and flare, central retinal thickness (CRT), and best-corrected visual acuity (BCVA) was investigated. Differences in these values were considered between pre-IVR and 1week and 1–3months post-IVR. Moreover, in patients with recurrence who received additional IVR, further changes in VEGF were examined. Main outcome measures: The end point of this study was BCVA, flare, and CRT at the fovea. Results: Significant improvement was seen in BCVA and CRT at all time points and in Flare at 1 vs 3months post-IVR; nevertheless, additional IVR was necessary in 94% of cases. In a patient with recurrence, CRT did not improve, even though VEGF decreased. Conclusion: Flare may be effective for estimating VEGF levels in aqueous humor pre-IVR. Inflammation-related molecules other than VEGF may be related to recurrence. Keywords: aqueous humor, branch retinal vein occlusion, flare, protein density, ranibizumab, vascular endothelial growth factor

Clarification of the degradation mechanism of photoluminescence (PL) charac-teristics of InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures on an InP substrate is studied to realize highly strained SL-MQW lasers with a large number of well layers. An unusual temperature-dependence of the PL peak wavelength is observed in the SL-MQW structure: the shift of the PL peak wavelength is reduced with change in measurement temperature. The degradation of PL characteristics is evaluated by the reduc-tion in the PL shift as well as an increase in PL linewidth and a decrease in PL peak intensity. The extent of the PL degradation increases with an increase in the number of well layers and an increase in strain. In the SL-MQW structure with degraded PL characteristics, the structure of CuPt-type atomic ordering is clearly observed for the first time in each barrier layer by high-resolution transmission electron microscope (HR-TEM) measurements. In the SL-MQW structure, neither dislocation nor three-dimensional nucleation is observed by TEM measurements. By increasing the growth temperature, elimination of the ordering structure as well as improvement in the PL characteristics have been confirmed even in the SL-MQW structure with a large amount of strain and a large number of well layers.

GaN films having distinct p-type conductivity, with hole concentration up to 4 × 10 16 cm 3 at RT, have been achieved for the first time. Samples were grown by MOVPE on a sapphire substrate using the AIN buffer layer. LEEBI treatment is found to be effective to lower the resistivity of the GaN:Mg, and to get the p-type GaN. The p-n junction LED, which emits UV light and violet-blue light at RT, is fabricated for the first time.

We achieved successful growth of a high quality undoped GaN film, in which photopumped stimulated emission at RT were observed for the first time. Different configuration measurements showed that stimulated emission occurred at about 83 meV lower than the peak photon energy of spontaneous emission, at RT.

High output-power and narrow spectral-linewidth operation of 1.3 /spl mu/m gain-coupled distributed feedback (DFB) lasers with InAsP buried absorptive grating are reported. In this report, we have investigated the effect of the thickness of separate-confinement-heterostructure (SCH) layer on the spectral linewidth. As a result, it was clarified that decreasing the thickness of SCH layer is effective to reduce the spectral linewidth. For the fabricated laser, a record high output-power of 230 mW and a minimum spectral-linewidth of 100 kHz was realized.

Characteristics of the InAsP layer formed on a corrugated InP substrate by a mass-transport mechanism have been investigated for use as the buried grating of distributed feedback (DFB) lasers, The size of the InAsP layer can be controlled by the height of the corrugation, and the arsenic composition in the InAsP layer can be controlled by the AsH/sub 3/ partial pressure. The results of TEM, EDS and PL show that InP is suitable as the buffer layer between the InAsP layer and MQW active layer. Fabricated 1.3 /spl mu/m DFB lasers which have an InAsP layer as an absorptive grating have shown low threshold current and high slope efficiency from -40-+85/spl deg/C, and high reliability has been demonstrated.

The dependence of photoluminescence (PL) characteristics on both SL-MQW structure and epitaxial growth condition is studied. The degradation of PL characteristics in the SL-MQW is confirmed as a broadening of PL linewidth and an unusual temperature-dependence of PL peak wavelength. By using a high-resolution transmission electron microscope (HRTEM), the structure of atomic ordering is demonstrated over entire barrier layers of the SL-MQW structure with degraded PL characteristics. By increasing growth temperature, elimination of the ordering structure as well as improvement of the PL characteristics have been confirmed even in a SL-MQW structure a with large amount of strain.

High output power and narrow spectral linewidth operation of 1.3 µm gain-coupled distributed feedback (DFB) lasers with InAsP buried absorptive grating is reported. In this study, we have investigated the effect of the thickness of a separate-confinement-heterostructure (SCH) layer on the single-mode stability and the spectral-linewidth property of 1.3 µm gain-coupled DFB lasers. As a result, we clarified that decreasing the thickness of the SCH layer led to stable single-mode operation at high output power and the reduction of the product of the spectral linewidth and the output power. For the fabricated gain-coupled DFB laser, a record high output power of 230 mW and a minimum spectral linewidth of 100 kHz at an output power of 150 mW were realized.

A new structure of 1.3 µm strained-layer multi-quantum well (MQW) complex-coupled distributed feedback lasers having an InAsP absorptive grating is demonstrated. In this structure, the InAsP absorptive grating and the strained-layer MQW active layer can be fabricated by a metalorganic vapor phase epitaxy process involving only one step. Furthermore, the fabricated laser has a low threshold current (16.8 mA) and a high efficiency (0.45 mW/mA).

A thin AlN buffer layer was proven to be effective on both sapphire A-face and sapphire C-face substrates for the preparation of high quality Zn-doped as well as undoped GaN. The nature of Zn-related luminescence centers and their density are strongly affected by growth conditions; especially by the substrate temperature, which must be lower than 950°C for the efficient formation of blue luminescence centers. Zn-doped GaN grown on a sapphire A-face was found to have a greater density of blue luminescence centers than that on a C-face, indicating that the A-face is superior to the C-face as a substrate.

Distinct p-type conduction is realized with Mg-doped GaN by the low-energy electron-beam irradiation (LEEBI) treatment, and the properties of the GaN p-n junction LED are reported for the first time. It was found that the LEEBI treatment drastically lowers the resistivity and remarkably enhances the PL efficiency of MOVPE-grown Mg-doped GaN. The Hall effect measurement of this Mg-doped GaN treated with LEEBI at room temperature showed that the hole concentration is ∼2·1016cm-3, the hole mobility is ∼8 cm2/V·s and the resistivity is ∼35 Ω·cm. The p-n junction LED using Mg-doped GaN treated with LEEBI as the p-type material showed strong near-band-edge emission due to the hole injection from the p-layer to the n-layer at room temperature.