That's too much info.
That makes me sad.
You can't be bothered to read this simplified web page. What ever makes you think you are going to understand what to do.
Why can't I buy some cheap, green laser from eBay and rapidly turn it on/off using a digi out pin
Well that page would have told you.
(assuming the voltage is not more than the required amount for the laser)?
Hint:- it is.