Improve switching speed for a <50mW laser with an Arduino and Transistor
As mentioned in the comments, it sounds like your laser has a built in current regulator that may not be intended to switch that fast.

If so, you might want to remove the driver from the laser and add your own 300mA switched current regulator. Something like this should work.







simulate this circuit &ndash; Schematic created using CircuitLab

Though watch the power dissipation. A 2N2222 is going to be marginal depending on the forward voltage of the diode. If need be, switch to a pair of higher power transistors.