Effects of Adhesive on Coupling Efficiency of Planar Light Waveguide Packaging

Problem statement: Advanced optoelectronic devices are a kind of key and basic components for next generation communication, untouched sensor, medical testing. They have lots of advantages including greater communication performance, larger capacity, and more fixable form. But light coupling and package structure seriously affects performance of optoelectronic devices. So a lot of attaching methods were proposed to package optoelectronic devices. A popular method which was widely used is a UV epoxy adhesive which can solidify the coupling interface with high mechanical strength and submicron displacement. In order to obtain high coupling efficiency, coupling approximation after adhesive is needed. Approach: In this study, firstly, the light coupling model was introduced. Then light beam propagation mode after adhesive with the same refractive index as that of light path was presented and the function modeling of couple model was derived. Finally, a slanted-plane structure of interface was considered and coupling approximation after adhesive was calculated. Results: Simulations and experimental results indicate that theoretical coupling efficiency and measured coupling efficiency agree with very well and the couple loss decrease about 0.4dB after adhesive. Conclusion: The matching adhesive could obviously increase the coupling efficiency and the approximation function could realize to predict the variation of coupling efficiency before or after adhesive accurately.