So I'm a sophmore in college working on a project, and I am stumped. The problem is this: I need to be able to control the opacity of some normally transparent material. So for example, I would have a transparent object sitting on the table, and when I shine a UV laser or an IR laser through it, the part that the laser is passing through of it becomes translucent, or any part of it becomes translucent. Another possibility would be if I applied a magnetic or electric field through the material, it would become translucent. The color it turns when it loses it's transparency would preferably be white or some light color. It must be able to change to translucent rapidly, to the degree of several nanoseconds, ~(10^-9 - 10^-7)s. And yes, it must be able to change back to transparent just as quickly. If anyone has any relevant information, including even the name of the property of material to adjust opacity, it would be greatly, greatly appreciated. Thank you for your time!