Push into the HTML header

What is the best way to ask the browser to prefetch a resource in an Ember.js application? The following code in the header of the HTML would do the trick:

<link rel="prefetch" href="http://ift.tt/1u6vnWS">

But I don't know what is the best way to push that code from within the Ember.js application to the HTML header.

I'm not talking about the boot time of an Ember.js application. I'm talking sometime during the usage. There are special scenarios where I know that the app will need a special resource after the next step. I'd like to preload that image/data/whatever at that time.