Research In Preparation And Characterization Of Ion-exchanged Glass-based Double-layer Multimode Optical Waveguide

With the continuous development of computer and communication technology, the traditional electrical interconnect technology gradually cannot meet the requirements of high-speed transmission of information because of its inherent physical limitations. Instead, optical interconnect will replace the electrical interconnect for data transmission and processing. Glass has the properties of good thermal stability, high dielectric constant and high transparency in a wide wavelength range. The ion-exchange technology based on glass has several advantages, including simple technology, easy operation, matched with standard fibers, good environmental stability and reliable performance. Therefore, ion-exchange technology has been widely used in the production of optical waveguide devices.In this paper, a kind of double-layer multimode optical waveguide structure is proposed and is studied in experimental and theoretical aspects. First, for the change in temperature of glass substrate due to the Joule effect in the process of field-assisted ion diffusion, the ion diffusion depth model can be established under different voltage. This theoretical model plays an important theoretical guiding role in controlling optical waveguide depth accurately during the field-assisted ion-exchange process.This paper has reported the fabrication of double-layer multimode optical glass waveguide through thermal Ag+-Na+ion-exchange and field-assisted ion-diffusion technology. Then, the properties of double-layer multimode optical waveguide, the cross-sectional dimension, diffusing depth, propagation loss and numerical aperture are tested. The first step is the fabrication of single-layer multimode optical waveguide and the test result show that the average of waveguide depth is58μm. Then, on the basis of the single-layer multimode optical waveguide, the upper and lower waveguide is aligned to produce the double-layer optical waveguide by using the alignment technology. The results of measurement under microscope indicate that the upper and lower waveguide dimensions are relatively close, the average depth of upper waveguide is about54μm, the average depth of lower waveguide is110μm, the interval between the two waveguides is30μm, and the dimension of upper optical waveguide is approximately29μm×17μm, the dimension of lower optical waveguide is nearly32μm×21μm. The observation of output optical field of upper layer waveguide and lower layer waveguide suggests that both layers are multimode optical waveguide. The tested results show that the propagation loss of upper layer waveguide and lower layer waveguide is respectively1.45dB/cm and1.37dB/cm, and the coupling loss of every end face is estimated to be0.85dB and1.08dB, respectively. The numerical aperture (NA) of the optical waveguide has been tested, the effective NA of upper layer waveguide in the horizontal and vertical directions are0.053and0.052, the effective NA of lower layer waveguide in the horizontal and vertical directions are0.052and0.046. Finally, according to the major problems, such as the glass substrate breakdown and the "silver line", the analysis of these two issues is carried out and also the solution to the problems is proposed.The results indicate that double-layer multimode optical glass waveguide has great application prospects in the field of optical interconnection and has important significance to improve the integration of optical devices and data transmission capabilities. In addition, the double-layer multimode optical waveguide can also be combined with other devices and technologies, which would improve the level of integration and generate some multi-functional optical devices.