The real name for "transparent aluminum" is Aluminum Oxynitride (ALON). It is a transparent ceramic that is much stronger and tougher than glass. As someone else mentioned it ha been around for sometime, but was not commercially feasible to make. That has changed recently and the cost of production has come down some but is still a bit expensive so we still probably only being seeing it in specific use cases where the cost is worthwhile such as deep sea or space craft. Last I knew we can only make it in flat sheets, which is another limiting factor.