Optical waveguides were prepared by the incorporation of silver or copper ions using the classical staining. We used commercially available soda-lime silicate and borosilicate glasses as substrates. Silver or copper stain was applied on a side of the glass substrates. The substrates were heat-treated at elevated temperature for various times. The treated glasses were optically clear and almost colorless except for a few samples stained for longer time. This indicates that silver and copper metal nanoparticles and Cu2O nanoparticles causing coloration of glasses were not formed in the glass substrates. The ion-incorporation process was approximately controlled by the diffusion of ions. We observed the propagation of 633 nm laser radiation by a prism coupling method showing that the glass surface region plays a role of waveguide. Refractive index change more than 0.01 at 633 nm was achieved in the waveguide layers.
We have been developing a technique of coloration and decoloration of glasses by photo-irradiation and heat-treatment for application to easily recyclable colored glass products. The mechanisms of the photo-induced coloration of glasses used in this research are a) the photo-induced defects (color centers) formation, b) the photo-induced change in oxidation state of ions, and c) the photo-induced formation of nanoparticles in glasses. The subjects for application of these phenomena to recyclable colored-glass products are presented. The research examples for each mechanism are presented in this paper as follows: 1) the effect of the doped Fe ions on the optical density and stability of coloration due to color centers, 2) the coloration by the change in oxidation state, (formula available in paper) and 3) the reversible coloration and decoloration for an Ag single-doped glass.
Decay curves of 1.5 micrometers (4I13/2) and 980 nm (4I11/2) emissions from Er3+ ions in Ga2S3-GeS2-La2S3 glasses were measured by the excitation of 1.5 micrometers laser diode pump. The decay curves were simulated using rate equations for a model consisting of four levels (4I15/2, 4I13/2, 4I11/2, and 4I9/2) of Er3+. A pair of unknown parameters, i.e., an excited state absorption coefficients for 4I13/2 yields 4I9/2, (sigma) esa, and a cooperative upconversion coefficient for (4I13/2, 4I13/2) yields (4I9/2, 4I15/2), C, were included in the rate equations. They were estimated by fitting the simulated curves to the measured ones. The obtained values were 3 X 10-21 cm2 and 1 or 3 X 10-21 cm3/s for the (sigma) esa and C, respectively.
Optical transition properties of Er3+ ions in ZnCl2-KCl-BaCl2 glass were studied and were discussed on the comparison with those in the other glass systems, i.e., ZrF4-based and Ga2S3-based glasses. Judd-Ofelt analysis was performed using eight absorption bands of Er3+ in the ZnCl2-based glass. Among the Judd- Ofelt intensity parameters, the (Omega) 2 was larger than that of the ZrF4-based glass. This is probably due to the covalency of the bonds of the rare-earth and ligand ions in comparison with those of the ZrF4-based glass. Decay curves of the emission from the 4F5/2, 4F7/2, 4S3/2, and 4F9/2 levels were measured. From the lifetime data and the radiative transition probabilities calculated using the Judd-Ofelt intensity parameters, multiphonon relaxation rates are estimated for the four excited levels. The multiphonon relaxation rates of the 4F5/2, 4F7/2, and 4F9/2 were much smaller than those in the ZrF4- based and Ga2S3-based glasses. This is the consequence of the extremely low-phonon-energy property of the ZnCl2-based glass. The multiphonon relaxation rates were inversely proportional to the exponential of the energy gap between the emission and the next-lower levels (a so- called `energy-gap low') as well as the other glass systems.
Glasses containing Er3+ ions of 0.3 to 7 cation mol percent were prepared in the system of Ga2S3-GeS2-LaS3. Frequency upconversion spectra of Er3+ in the glasses were measured under the excitation at 800 nm and 980 nm. Green emissions at 533 nm (2H11/2yields4I15/2) and 552 nm (4S3/2yields4I15/2), and red emission at 665 nm (4F9/2yields4I15/2) were observed.In addition to these emission bands, 497 nm emission assigned to the 4F7/2yields4I15/2 transition was observed. The spectral properties are analyzed from the view points of low phonon energy property and high refractive index.