Laminated Safety glass
Comes in all different types. The most popular for doors is 6.4 Laminated or toughened glass. 6.4 laminated is 6.4mm thick and if it was going to be put into a door then the rebate would need to be able to take this size glass. However, both clear and obscured glass can be toughened. These come in a 4mm range which fits into almost all doors and is perfectly safe.