Copper Ion-exchange Glass Planar Waveguides And Their Blue-green Luminescence Propetries

Ion exchange technique is a very important method for fabricating glasswaveguides. The alkali ions are replaced by other cations （typically Ag⁺, K⁺, Li⁺,Copper ions etc.） through immersing the glass substrates in a molten salt bath duringthe ion exchange process in glasses. It has been extensively researched in the case ofsilver and potassium ion-exchange. In recent years, copper-containing glasswaveguides have attracted much attention, owing to its blue-green luminescence.These characteristics of copper-containing glass waveguides make it possible tointegrate both the passive and active waveguide components on one single substrate,which is of great significance in integrated optics structures and laser devices.Glass planar optical waveguides were fabricated by copper ion-exchangetechnique. Refractive index （RI） profiles of waveguides were reconstructed by prismcoupling method and Inverse WKB method. Cu⁺and Cu²⁺ion concentrations werecalculated by solving diffusion equation, and the mechanism of RI changes wasanalyzed as well. The model between the RI and ion concentrations was proposed bytaking both Cu⁺and Cu²⁺into account according to polarizability changes among Cu⁺,Cu²⁺and Na+. The results show the contribution of Cu²⁺can’t be negligible, and thereason for the RI change is both Cu⁺and Cu²⁺. With exchange time increasing, theredox process between Cu⁺and Cu²⁺will play an important role on RI profiles.Then the prepared samples were annealed in air for1h at various temperatures.The RI profiles and the photoluminescence spectra of the annealed were discussed,comparing with the samples without annealing. The RI changes were decreased afterthe annealing process. The annealing process gives rise to a re-diffusion for thecopper ions，which changes the RI of the waveguides. The photoluminescence spectraof the samples were measured at room temperature. All the prepared samples andannealed samples exhibit a strong blue green photoluminescence centered at510nm atan excitation wavelength286nm. It is observed than both the fabrication conditionand the annealing process influence the photoluminescence properties, suggesting a correlation between the Cu⁺/Cu²⁺ratio in the glass and the photoluminescenceintensity level. The photoluminescence intensity will increase first and then decreasewith the ion-exchange time increasing. Annealing will increase the intensity. Theincrease will be more obvious at higher annealing temperatures.