Current modulator for laser driver and analog audio signal modulation
You can analog modulate the laser diode as long as you do not saturate the MOSFET fully ON or OFF with too strong a signal, as this will disrupt the constant current loop and risk burning up the laser diode. Also the MOSFET will get hot due to being in a linear region during analog transmission.

You can use the circuit in the link but C2 should be 1uF with (+) side facing op-amp. Also change R5 to 20 ohms to get closer to your expected idle current for the laser diode. NOTE: If all resistors are 1% and capacitors are 5% quality Polypropylene or Mylar then results will be much closer to expectations. Do not increase C2 to get a deeper bass, as bass has a time constant longer than your servo loop can correct for. If it is unstable with C2 = 1uF then C2 can be no larger than 100nF.

Count on mounting the MOSFET to a medium heat-sink about 1"\$^{3}\$. If heat-sink gets too hot to touch add a small cooling fan about the same size as the heat-sink, or 2" sq at most, and make sure it can run on your local DC supply, plus or minus a couple of volts. It must blow cool air into the heat-sink.