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Blue up-conversion fluorescence from the Tm 3+ : 1 G 4 → 3 H 6 (480 nm) transition has been observed from calcium aluminate glass codoped with Tm 3+ /Nd 3+ , The mechanism for the up-conversion process consists of a two-photon process. An excitation beam with a wavelength of 791 nm first excites Tm 3+ to the 3 H 4 level, where Tm 3+ again absorbs the 1060 nm emission from Nd 3+ : 4 F 3/2 → 4 I 11/2 to attain the Tm 3+ : 1 G 4 level. Lifetime and intensity variations with compositions suggest the presence of an efficient energy transfer from Nd 3+ to Tm 3+ , The highest 480 nm emission intensity has been obtained from the glass with 0.1 mol% of Nd 2 O 3 and 0.2 mol % of Tm 2 O 3 .

Emission properties of 2.0 μm fluorescence and the energy transfer between Ho3+ and Tm3+ in 57PbO·25Bi2O3·18Ga2O3 (mol%) glass codoped with Ho3+ and Tm3+ were investigated. Cross-relaxation rates in Tm3+ increased approximately 5 times when the Tm2O3 concentration was increased from 1.0 to 1.5 wt%. Coefficients of the forward Tm3+→ Ho3+ energy transfer were about 15 times larger than those of the Tm3+← Ho3+ backward transfer. Analysis of the energy transfer and gain spectra indicated that the highest gain at the 2.0 μm wavelength region could be achieved from the glass with 1.5 wt% of Tm2O3 and 0.3 wt% of Ho2O3.

Ge–Ga–As–S glasses were investigated to develop efficient host materials for the Er 3+ :2.7 μm fiber lasers. Ge30Ga1As9S60 and Ge30Ga2As6S62 (all in at.%) glasses show good thermal stability and high rare-earth solubility up to 0.3 mol%. Mid-infrared emission with a peak wavelength of 2.76 μm and bandwidth of ∼120 nm was observed in Er3+- and Er3+/Tm3+-doped Ge30Ga2As6S62 glasses. Codoping of Tm3+ significantly reduced the lifetime of the Er 3+ : 4 I 13/2 level due to the energy transfer of Er 3+ : 4 I 13/2 → Tm 3+ : 3 F 4 . Thus, the population inversion between the 4 I 11/2 and 4 I 13/2 levels in Er3+ became possible. In Er3+-doped glasses, the rate of cross-relaxation for the 4 I 11/2 level was approximately 11 times faster than that for the 4 I 13/2 level.

The 1.48-μm emission properties and electron population densities of the excited levels were investigated for Ge–As–Ga–S glasses doped with Tm3+ or Tm3+/Tb3+. Electron population inversion between the 3H4 and 3F4 levels in Tm3+ cannot be achieved without Tb3+ addition due to the strong cross-relaxation in Tm3+. Co-doping of Tb3+ resulted in the large decrease in the population density of the Tm3+:3F4 level via the energy transfer of Tm3+:3F4→Tb3+:7F0,1,2. Calculated population densities of the two levels in Tm3+ using the rate equations showed that the population inversion became possible through the addition of Tb3+.

It is well known that the imperfections in thin film optical devices would cause absorption, radiation, and scattering loss of the guiding beam, and such losses are mostly unavoidable. To reduce the propagation loss, the conditions for film deposition should therefore be optimized. Yttria (Y2O3) thin film was chosen for the study. Yttria thin film waveguide was deposited on silicon and thermally oxidized silicon wafers by reactive sputtering in a rare gas–oxygen discharge. The deposition process was controlled by the substrate temperature, total gas pressure, oxygen flow rate, and rare gases (Ar, Ne). The yttria thin films were characterized for the optical losses based upon the film structures. Relationships between deposition parameters and the propagation losses were discussed.

Ge 25 Ga 5 S 70 (at.%) glasses doped with Tm 3+ and Ho 3+ were prepared and their emission characteristics were evaluated with an emphasis on the 2.02 μm fluorescence from Ho 3+ : 5 I 7 5 I → 8 transition. With constant Ho 3+ concentration, intensities of 2.02 μm emission through the excitation of Tm 3+ at 798 nm increased with Tm 3+ content which indicates efficient energy transfer from Tm 3+ to Ho 3+ . Rates of energy transfer also increased with Ho 3+ concentration but competed against the upconversion phenomenon both in Tm 3+ and Ho 3+ .

XPS Ols spectra were recorded for glasses in the binary PbO-Ga2O3 and ternary PbO-Bi2O3-Ga2O3 systems. Large shoulders with chemical shifts of 1.4 to 1.9 eV were observed in the Ols spectra recorded from PbO-Ga2O3 glasses. These shoulders were attributed to the presence of nonbridging oxygens in the structure. The shoulders indicated that, contrary to previous results, PbO was a network modifier as well as a charge compensator and network former. The addition of Bi2O3 reduced the number of nonbridging oxygens and, therefore, it was classified as an intermediate. Ga2O3 seemed to form GaO4− tetrahedra, constituting the backbone of the network structure. Glasses in the PbOBi2O3-Ga2O3 system had their IR cutoff edges located at 7 μm with glass transition temperatures in the range of 320° to 400°C.

(CdAs2−xGex)0.8I0.2 (where x = 0.0–0.4) infrared transmitting glasses were prepared and the effect of Ge on their properties was investigated. The glass-transition temperature, Tg, of these iodide glasses is as high as 300°C which is considerably higher than that of existing iodide glasses. These glasses exhibited a relatively good chemical durability against water and nitric acid. The density and crystallization phenomenon indirectly suggested that the maximum Ge solubility is less than x = 0.2. These new thermally stable glasses show infrared transmittance up to 17 μm which offers a potential for future mid-infrared applications.

Research and development on materials has emerged globally from the urgency for advanced materials to meet the challenges of the 21st century. Research activities have been continuously intensified in both academic and research institutes around the world and Korea has been no exception. MRS-Korea has been recently formed with the support of MRS-Japan and -USA. The global efforts in MR activities have been intensive, and paved the way for the MRS-international campaign. Current materials research in Korea encompasses mainly advanced materials (bulk, single crystals and thin film oxides, metals, and composites) as opposed to traditional materials (clay, metals, less refined materials). This article outlines the MR activities in Korea, for the benefit of MRS-international, and gives a brief history with emphasis on scientific programs. In the research community, the recent trend of MR activities has been moving towards cooperative research such as through industry-university, industry-institute, university-institute, and triads, industry-institute-university. Such types of activities are often referred to as consortium approaches, and are currently very popular throughout the world. Examples of such activities are given and the pros and cons of each system are discussed.

Chalcogenide and heavy metal oxide (HMO) glasses doped with various rare-earth elements have beenstudied for the possibility of developing new solid state laser materials to operate in the mid-infrared. Thisstudy investigates the synthesis and optical characterization of As2S3 and BiO3-PbO-G;O3 glasses doped with rare-earth elements Nd, Er, Ho, Dy, Pr and Tm. Absorption and fluorescence spectra of glasses doped with rare-earths confirmed the presence of trivalent rare-earth ions in the amorphous mathx. As2S3glasses doped with 0.4wt% Nd showed strong fluorescence at 1 .09 and 1 .38.tm, while glasses dopedwith 2.Owt% Dy exhibited fluorescence at 2.98 and 4.40p.m. Further, doping of Ho up to approximately2.Owt% showed fluorescence at 2.01 and 3.92gm. 1 . INTRODUCTION Doping of rare-earth elements into the low-loss silica-based optical fibers has attracted an increasinginterest for the purpose of developing active optical devices. These devices can generate, modulate oramplify the optical signal as opposed to the passive components which simply transmit the optical signals