Self-assembled growth of quantum dots by molecular-beam epitaxy is used to form the active region of a vertical-cavity surface-emitting laser (VCSEL). Ten layers of InGaAs quantum dots are stacked in order to increase the gain. This quantum-dot VCSEL has a continuous-wave operating current of 32 mA at room temperature. Emission spectra at various current injections demonstrate that the lasing action is associated with a higher-order transition in the quantum dots.

No abstract

No abstract

No abstract

Two kinds of naphtols, 2, 7-dihydroxynaphthalene (2,7-DHN) and 2-hydroxy naphthalene (2-HN), were reacted with formaldehyde to produce dimeric naphtols. One of the products, designated as DN-a, was prepared only from 2-DHN and thus possessed tetra-functionality. Two other kinds of dimeric naphtols, DN-b and DN-c were prepared from the mixture of 2-DHN and 2-HN in different ratios providing hydroxyl functionalities of 3.0 and 2.6 for DN-b and DN-c, respectively. The epoxy resins, E-a, E-b, and E-c, were prepared by the reaction of the corresponding dimeric naphtol with epichlorohydrine. The melt viscosity of E-a was comparable with that of cresol novolac type epoxy resin (ECN), and those of E-b and E-c were sufficiently lower so as to provide better flow-ability in comparison with ECN making them potentially more useful. The cured epoxy resins in this report showed higher T g values in comparison with that of ECN. In particular, the E-a cured resin showed a T g of 328 1 C, which is the highest T g for epoxy resins reported so far.