think this is because of the duty cycle:
No it is not.
The problem is :-
I thought I could put a resistor to get those 3.3V.
Using a single resistor to reduce a voltage is wrong. It will only give you a consistent voltage drop if the current from the device is constant, which it rarely is.
Driving a Laser is not easy, it is not simply of shoving a voltage at it, you normally need a special driver. You also need to know what current the Laser would normally take giving it 3V3. This page has a lot of good advice about driving a Laser.
http://www.repairfaq.org/sam/laserdps.htm