Journal of Light
&
Visual Environment

Volume 29 Number 2, August, 2005

CONTENTS

Papers

Research Notes

Committee Report

English Abstracts

 Optical gain in as-grown SiO₂ thin film con-taining silicon (Si) and Germanium (Ge) nanocrystals, grown by rf-sputtering, is de-monstrated by applying variable stripe length (VSL) method. The Si and Ge nanocrystals were grown while depositing the thin film and no annealing was required to form the nanoc-rystals. The optical gain in the thin film is de-monstrated at 400 nm, at which the film shows photoluminescence peak. The analysis of the experimental data, based on one dimensional amplifier model, yields the gain value of 4.3 cm_-1 for a film of 738 nm thickness, when excited by a continuous wave 325 nm wavelength He-Cd laser.

KEYWORDS : optical gain, silicon, germanium, nanocrystals

Measurement of Complex Refractive Index of Tung-sten by Using Ellipsometry
— Study of the Accuracy of Ellipsometer —
A. SATO, S. SEKINE and M. OHKAWA

 Tungsten microcavity light sources and tungsten cluster light sources have interested us as light sources for next-generation having high luminous efficacy and long lifetime. The complex refractive index of tungsten requires the operating temperatures from 2000 K to 6500 K to evaluate the luminous efficacy and lifetime. Little is, known however, about the complex index of tungsten at such high tem-peratures. Since ellipsometry has a non-contact measurement technique, the complex refractive index of any metal can be measured even under extremely high temperature with high accu-racy. We consider that ellipsometry is an effec-tive measuring method. We thus designed and fabricated the ellipsometer to measure the complex refractive index of tungsten at room temperature. As the result, we established the ellipsometer improved from measurement of the complex refractive index of tungsten from 2000 K to 6500 K. In this paper, we report on the problems to measure the complex refractive in-dex of tungsten using the ellipsometry, and the achieved accuracy of measurement.

KEYWORDS : microcavity light source, cluster light source, tungsten, complex refractive index, ellipsometry

 This paper presents new circuit of the electronic ballast based on neutral-point-type back-boost in-verter for compact fluorescent lamps. Electronic ballasts for compact fluorescent lamps don’t need to satisfy the IEC standard Class C, and the regulation is looser than it. However, it is impor-tant to reduce the harmonics of input current, be-cause the compact fluorescent lamp seems to be used widely in future. This paper shows analyses of circuit operations and experimental results, and proves that the proposed circuit is effective for reduction of harmonics of input-current and also effective for improvement of input power factor.

KEYWORDS : electronic ballast, neutral point type inverter, compact fluorescent lamp, IEC class C

 This report summarizes the works of the Re-search Committee on “Optimum Facade Type Considering Light and Visual Environment” (from October, 2000 to March, 2003).
 The use of daylight to replace or supplement electric lighting in commercial buildings can re-sult in significant reductions in energy and de-mand. Façade design is one of the determinants for use of daylight. In order to assist designers who intend to use daylight in buildings, the com-mittee provides a brochure showing the effects of window conditions on light and heat introduced in buildings visually and plainly. Also, the commit-tee reviewed the level of technology of the tech-niques for utilizing daylight.

KEYWORDS : facade, simulation, solar gain, Ex-panded AmeDAS weather data