I had an idea to modify my previous multipass test to see if we could get a sense of the maximum depth you can cut when taking multiple passes on a piece.  Previously I had cut part of a line at 100% power in one pass, the next at 50% power in 2 passes, and so on.  This time I left the power unchanged and just increased the number of passes.  In this case I settled on 200 mm/min, 40% power, and a 0.25 mm stepover using my NEJE A40640 laser module cutting into a 19mm thick piece of basswood.

After letting it run for 12 passes and cleaning up the edge a bit we get the cut above.  You can see there is a thinning of the cut with depth.  I think this is highly dependent on the density of the wood, with the laser taking the path of least resistance rather than always cutting straight down as you would expect.

It is difficult to measure the last cut reliably since it has gotten quite thin.  I suspect if I re-ran the same test with 10 passes we would see that depth cutting as well as the ones above it, with the extra space provided by the additional passes.

Anyway you can see from the rough measurements above that the change in depth is fairly linear although we steadily loose a bit of depth with each pass.  I had run this same test at 80% power and 150 mm/min but it was burning completely through the wood in only 3 or so passes.  This laser is quite capable of cutting soft woods like basswood.  I need to get out some thicker Baltic birch plywood and see how well it performs with that.