Hi Vijay,
Unfortunately we have not built that feature yet. It is on our backlog of items to implement (pop-up auth) but it is not currently available. You can however do your own implementation of it by opening the target in a new window yourself. I have written
a blog post on it on our MSDN blog last year:
http://blogs.msdn.com/b/healthvault/archive/2012/01/31/healthvault-auth-in-a-popup-window.aspx