A novel technology for formation of a narrow active layer in buried heterostructure lasers by single-step MOCVD

A new technology of fabricating a buried heterostructure laser with a narrow active layer in a single-step MOCVD process other than the conventional two-step process is proposed. The technology is based on the separate growth on the undercut ridge. The anisotropic growth has been found to be very useful for formation of a very narrow active region in a self-aligned manner. The novel RBH laser implemented by the single-step MOCVD process has been proposed. The RBH laser has exhibited CW lasing oscillation with a threshold current as low as 30 mA at room temperature and with the circular beam spot.     

Monitoring of laser processing using induced current under applied electric field on laser produced-plasma

A new electrode circuit for measuring the induced current from laser plasma produced during laser material processing has been devised. The new electrode circuit has greatly increased the possible separation between the electrodes and the workable probing distance of the electrodes from the processed sample surface, namely 38 and 22 mm, respectively, sufficing the requirements of actual industrial laser material processing, avoiding direct contact of the electrodes with the big plasmas and profound sputtering. Several possible electrode configurations were investigated to accommodate the specific needs of the actual laser processing. It was shown that this technique is a very effective tool for accurately determining the moment of completion of penetration, as required in the laser piercing process. In contrast to this, the optical method currently in use cannot accurately determine the piercing completion moment due mainly to the disturbance from smoke arising at the processing point. A preliminary work using a CW CO₂ laser normally used in the actual industrial material processing was also made, resulting in a strong induced current signal corresponding to the laser pulse duration and frequency. The signal was successfully used for monitoring the penetration completion in a stainless steel plate drilling process. This reveals that this technique can be used for monitoring actual industrial material processing using high power lasers.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

A competitive evaluation of urban energy systems from viewpoints of energy conservation and mitigating environmental impact

Although various energy system alternatives for business, commercial, and residential customers have recently been developed in order to reduce energy consumption and CO₂ emission, it is important to evaluate competitive characteristics among such new energy system alternatives quantitatively, in consideration of tradeoff relations among economic cost, energy consumption, and CO₂ emission. In this paper, using multiobjective optimization model for urban energy system planning, two competitive evaluations are performed. One is the break‐even cost analysis for introducing more efficient, but more expensive energy equipment, such as photovoltaic system and fuel cell system. The other is that we evaluate the competitiveness of a certain energy system from the viewpoint of a whole urban area because there are multiple alternatives for attaining the same target of reducing CO₂ emission of energy consumption. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 71–79, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20421