The last board I made is a filter for the power supply feeding the previous boards. As with any electrical project it's vital that we have a clean power supply, and in particular we want to avoid burning our lasers.

I'm using mostly big through hole components here, following this schematic:

And here is the finished board:

The big question of course now is whether it actually filters and how much. I don't have access to a network analyzer that goes to very low frequencies, so here's what we're going to do instead:
Make a function generator send a 1V peak-to-peak sine wave with a 1V offset (so we don't annoy the electrolytic capacitors too much) into port P1. Then look at the output at P2 with a scope reading off Vpp at the frequency we set on the function generator.

OK, so our filter blocks pretty much everything above a few tens of Hz with the -3dB point at around 10Hz! Promising!