deletions | additions       diff --git a/Liu_et_al_reports_on__.tex b/Liu_et_al_reports_on__.tex  index c08c960..3c14bfc 100644  --- a/Liu_et_al_reports_on__.tex  +++ b/Liu_et_al_reports_on__.tex 
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Liu et al reports on waveguide integrated Ge p-i-n photodetectors using a silicon-on-insulator platform. A question that needs to be answered in how to be able to couple light into the intrinsic layer. Specifically they use butt-coupling and a vertical coupling scheme. Butt-coupling using a Silicon waveguide to couple light directly into the Germanium and vertical coupling using evanescent waves(surface waves) to couple to Germanium. Figure 14 shows the setup used to measure the responsivity of the photodetector. Responsivity is measured from the equation \[R=\frac{I_{ph}}{10^{\frac{\gamma L}{10}}P_{out,ref}}\]