Research Of Refractive Index Profiles Of Single Mode Ag-Na Ion-exchange Planar Waveguides And Photoluminescence Of Copper Ion-exchange Waveguides

In this work, we are concerned about the refractive index profiles of single mode Ag-Na ion-exchange glass planar waveguides and the change of refractive index and photoluminescence in copper ion-exchange glass planar waveguides. The history of ion-exchange is introduced. Then, we analysis the theory of ion-exchange and diffusion equation, and introduce the method for describing waveguides. The detail is as follows:1) Determination of refractive index profiles of single mode Ag-Na ion-exchange glass planar waveguidesThe Inverse-WKB method is mostly used for the determination of refractive index profiles of planar ion-exchange waveguides. In Inverse-WKB method, there must be no less than three modes, and the method is not useful for single mode planar waveguides. However, there are disadvantage in the existing methods for single mode planar waveguides. Some destroy the waveguides; some use light interferometry method which is complex; some use complex method of double-wavelength which need the difference of refractive index in different wavelength, though we can get the difference; some use multi-wavelength method in which the tunable lasers are expensive.First, we designed a new method for determination of refractive index profiles of single mode ion-exchange glass planar waveguides, and proved the veracity. In experiment, glass planar waveguides were prepared by Ag-Na ion-exchange technique. The profiles of refractive index were measured by means of prism-coupled and Inverse-WKB method. Using a polynomial method for the simulation of the relationship between the refractive index change and the concentration of silver ions,we got the refractive index profile of the single mode planar waveguides. The refractive index profiles obtained by this methodΔn = kΔc are consistent with Gaussian distribution by using variance of depth of adjacent refractive index. Without destroying waveguides, the conditions of the experiment are easy and the calculation is understandable in this method.2) Photoluminescence in copper ion-exchange glass planar waveguidesThe copper ion-exchange process is widely used to fabricate planar, channel and buried waveguides and copper-containing waveguides have blue-green luminescence, so copper-containing waveguides have recently attracted much attention. In this work, we fabricated planar waveguides on soda-lime glass substrate by Cu-Na ion-exchange technique. Then, we measured refractive index profiles and excitation and emission spectra of the waveguides. With the time increasing, we found that the number of the modes increased, and then decreased, at last disappeared. The intensity of emission was the same, which didn't monotonous increase with time increasing. The increase of refractive index and blue-green luminescence are related with Cu~+. The reason for the change of the number of modes and photoluminescence is the transformation from Cu~+ to Cu~2. Therefore, we should choose a suitable time if we want to get a suitable waveguide. The number of modes and the intensity of photoluminescence can not be increased by only increasing exchange times.