The problem with that being mirrors REFLECT radiation, not absorb or redirect it. Even if you carefully shape the mirrors to redirect it somehow, you'll still have made yourself more visible in at least one direction. Concerning shielding particles, there are two problems: The first is density. This being vacuum, maintaining a dense enough cloud would be difficult. Maybe use magnetic particles so they attract eachother? The other, bigger problem is laser ablation and it's usefulness as a thruster. The particles may absorb some energy, but a weapon's grade laser would start vaporizing the exposed sides, essentially acting as a tiny thruster. So a spacecraft cowering behind it's cloud-wall would receive a weakened laser, depending on the absorbing and radiating ability of the particles...and then a good portion of the rest of the laser's energy, in the form of "micrometeorites" being driven along by the laser. That being said, spreading out such a cloud would make good chaff. It wouldn't be stealthy, but you can keep the gunners guessing...