I really hate to post this, but first how many amps does that looks like a laptop 12 volt power supply put out? I had a laser diode project that looked just like yours except for the little circuit board.... the diode I had was rated at 5 watts and the power input was limited to either 3 or 4 amps. I wasted a Lot of time and extra money getting it to work. It kind of worked but was very disappointed. It was slow and the dot quality was very poor. Your PWM or TTL signal comes from your controller board as Mach 3 or whatever. PWM for grey scale never happened and but the TTL did work on mine.
There are people using a Arduino board and gerbil like > Grbl - A Quick CNC Wiki I might have some stuff still around I would sell for cheap,