Do I need a driver for a single laser?
Looks like you don't need a driver.  You will, however, need to deal with the extra voltage.
From the first Q&amp;A on your link:
&quot;There is a 92 Ohm tiny resistor (I did measured 92 Ohm with my Ohmmeter) at the back of the Led, in series with the actual Led device. So with a 5V tension source connected on both wires, you get 20mA through the circuit, spliting as about 2V at the resistor and 3V at the led (2.7V is the expected value).
What this means is they are safe to connect directly to a 5V source as they are, as the included resistor will limit the current.&quot;
Since you want 20mA through the diode, and you have a 9 V source...
We will need to drop:
$$9\ V - 2.7\ V= 6.3\ V$$
With resistors.
Using Ohm's Law, we know R=V/I:
$$\frac{6.3\ V}{0.02\ A}= 315\ Ω$$
And we know we already have 92 Ω:
$$315\ Ω-92\ Ω=223\ Ω$$
So a 220 Ω resistor may work, but you might want to use a 270 Ω or even 330 Ω resistor to be safe.
This resistor should be in series with the diode.