I mean there are lots of ways to do it, since you specifically said you want the engraved portions to be black, let’s go with that.
Option # 1: Generally speaking you’d engrave the glass and fill in the dark areas with a black paint or something. This is a lot like painting tiles, I’d suggest searching the forum for tile projects.
Option # 2: mask the glass, score and weed (or engrave) the masking away, then paint the entire surface. Peel away the masking you left behind and you get a nice crisp painted image. This was recently discussed in an acrylic dice tower thread. Dice Tower of... ...the Damned ...the Dead ...Rolling ...Madness
Option # 3: Get a vinyl cutout (not with your laser) of the image in question, and transfer that to the acrylic or glass. This would be very sharp, but the laser can’t cut PVC, which is what most vinyl films are made of. You’d use something like a cricut or silhouette to do that yourself, or perhaps farm it out to a custom vinyl cutter like a sign shop or some online service.
Anyway, these are just a few of the possibilities, there are lots of ways to get this done, each with their own tradeoffs.