Here some updates:
Part of cabling soldered on the Nano. D13 Laser TTL, D12 Servo signal, 5V and ground
More stuff in the box. The small yellow board contains an 7805 voltage regulator to have 12V and 5V
Still waiting for the stepper and the dc motor to continue the work.
Additionally I am thinking about driving the DC motor through a PWN and transistor to regurlate the speed.
To calibrate the stepper mirror at startup I am thinking about an attached phototransistor on the side.