content_image/335743.jpg
<img src='content_image/335743.jpg'>

is small because F is so large that Eq. (3) can be well approximated by S/S o = F η$_{a}$/η o . Since η$_{a}$ does not change much compared to F , it turns out that maximizing F and S/S o give similar values for b . This can also be inferred from the quantum efficiency η , which is shown by dashed curves in 3. η is close to η$_{a}$ , corresponding to the curve for η o = 100%, even when η o = 5%. For smaller Purcell factors, the difference between the optimal b for F and for S/S o would be larger and vary with η o . 

