A petabit is equal to 128 terabytes

I don’t really feel like I’m much the wiser, having read this, on how exactly this works. It’s storing data in 3 dimensions in layers and uses 2 lasers in both write and the read process. Why multiple layers in 3 dimensions over a single layer as in traditional optical media would yield better storage density is intuitive but the way they’re able to do this is not that well explained. I don’t understand the relationship between having 2 lasers and being able to store data in many layers. The fact that one laser disables the effect of the other both in read and in write is confusing, one would think “switching off” the writing process done by… not writing anymore, rather than having a second laser which somehow disables the first but in any case the effect of this is said to allow “spots” (are they like pits?) smaller than the wavelength of the light used to create them which is presumably very small and again makes intuitive sense as to how that would allow increased density and thus storage capacity but doesn’t help explain the 3 dimensionality. Also, how does firing a laser at a material presumably burn it away to produce a “spot” (pit?) but firing a second laser at it stops this from happening? Similarly, with reading, how does firing a laser at a spot cause it to fluoresce, yet firing a second laser at it somehow causes it to stop doing that? How bizarre.

On an even more basic level, how do layers work? How does the outer most layer of the readable surface of the disc not block or interfere with the ability to read or write the next layer beneath it and so on?