Well, there is a great book coping with that thought-provoking issue of Implied Author and Empirical Author. It's made up of six lectures held at Harvard University in 1992-1993.
The title is: "Six Walks in the Fictional Woods", by Umberto Eco.
It deals mainly with prose fiction, but the issues Eco tries to deal with are valid for poetry as well. He is a professor of Semiotics, anyway -- so he mainly talks about the processes involved, exploiting a huge amount of examples from prose fiction.
 
Sara