another commenter melodic had this to say:

Laser diodes need constant current, so any extra voltage that the driver and laser diode don’t use gets turned into waste heat in the driver. That extra 5V times nearly the half an amp that the circuit is taking puts an extra 2.5W into the driver, which is unnecessary. 7V is enough to power the circuit/laser without causing overheating!

We hope you enjoyed this video and don’t try this at home without the supervision of a professional.  Lasers are cool and can be very dangerous so definitely consult and only work with safety pros when it comes to these types of experiments.

We look forward to posting more videos from this experimenter.