What are laser diode drivers used for
Some important features of many laser drivers:


Constant current output
Input voltage transient protection
ESD protection
Controlled turn-on ramp rate


Many will also have a control loop taking feedback from a monitor photodiode to provide constant optical power output rather than constant current output (which will result in varying output power over temperature and laser aging).


  can this be done directly from a PCB circuit board.


Laser drivers are normally implemented on circuit boards, so yes.


  And I am wanting to pulse it at 1ns or faster.


Pulsing a 5 mW laser at 1 ns is not an entirely simple problem to solve. You will need to carefully control the parasitics in the connection from your driver circuit to the laser to avoid ringing that could damage the laser.

You'll also have to account for the laser's internal capacitance, which will likely prevent switching it so quickly without at least using some kind of pulse shaping on the driver output.