I don't think that there is any server side code that could help you with this. You cannot open a new browser window for the response from the server.
You can however get the response in a new window at the client side. In case of links and forms it is a simple matter of adding target='_blank'. Just one points here,
1. target attribute is Deprecated - so its a bad practice to use it.
Though this will work it is not the best way to do it - it is not valid HTML.
Why not - its still an legal HTML attribute right (Deprecated does not mean illegal)? I agree it bad but so is window.open() - putting in JavaSciprt inside a anchor tag so that its valid XHTML seems equally bad.
I was trying to look for it but could not find the reason why the 'target' tag is depreciated - anyone has an idea?