If this is your first laser build here is a great place to start.
Diodes are current hungry and as they heat up their internal resistance is lowered causing them to want to draw more current. Don't attempt to connect the diode directly to a fixed voltage source like a battery. You must use a "constant current" power source like a current limiting driver or variable current power supply with the current limited to no more than 1.8A or you diode will suffer thermal runaway and die. For more info on the reason for a constant current driver see this thread.
Laser Driver - It Can Be Done!