$.ajax calls are supposed to receive the response and do something, by sending it a 'success' function.
So I think the best to do in your case is return the full URL (with http://) and do this on your ajax request:
$.ajax({
type: 'POST',
url: '/resultat',
data:{
parametres : params,
success : function(response){
window.location.href = response;
}
});