Glasses for Novel Photonic Applications
허종 교수
포항공과대학교

Glasses have been used for building and automobile windows, substrates and covers for various displays because of its high transparency in the visible wavelength region. There are still a number of emergent technologies that heavily rely on the development of innovative optical materials and devices. Typical examples of these areas are fiber-optic communication, LEDs, night vision, Infrared lasers and light sources, to mention a few.
Chalcohalide glasses refer to glasses composed of both chalcogen and halogen components. They are being investigated for wide infrared windows as well as for hosts of many rare-earth ions. One of the major issues is to reduce the multiphonon relaxation from the emission level of rare-earth ions. Author’s group was able to control the multiphonon relaxation in Ge-Ga-S glasses by adding alkali halides. For example, intensity of the 1.31um emission from Dy3+ increased sharply at the expense of the 1.75um emission intensity when the appropriate amount of alkali halides was added. Alkali halides added to Ge-Ga-S glasses modified the phonon vibration through the formation of [GaS3/2Br]- subunits that directly affect the non-radiative transition in rare-earths.
Semiconductors nanocrystals, in particular lead chalcogenide quantum dots (QDs) also provide potentials for near-IR lasers, color convertor for light emitting diodes (LED) and fiber-optic amplifiers because of their size dependent optical and electronic properties. It is particularly important to control the sizes of QDs precisely since their optical characteristics are critically dependent on the diameters of QDs precipitated. In addition to the conventional heat treatment technique, various methods were proposed for the efficient and precise control of the sizes of QDs. By optimizing the concentration of Nd3+ ions in glasses, wavelengths of the photoluminescence from PbS QDs were controlled to 1~2 um range that match the fiber-optic telecommunication window. Irradiation of the green laser assisted the formation of CdSe/Cd1-xZnxSe core/shell structure inside the glass that significantly decreased the adverse emission at λ=620 nm associated with the surface defects. Presentation will review the several methods designed to control the size, shape and spatial distribution of quantum dots in inorganic glasses.