facebook get profile picture after user logins into website

FB.api('/me', {fields: 'id,name,email,picture'}, function (response) {
    var picture_url = picture.data.url;
});

FB.api("/me", {fields: "id,name,picture"}, function(response)
{

    FB.api(
            {
                method: 'fql.query',
                query: 'SELECT pid, src_big, src_big_height, src_big_width FROM photo WHERE aid IN ( SELECT aid FROM album WHERE owner="' + response.id + '" AND name = "Profile Pictures")'
            },
            function(data1) {
                alert( data1[0].src_big );
            }
    );

});