Photodiode robust enough for laser?
The photons from a red laser aren't any more energetic than those from a flashlight. Red light corresponds to a photon energy of 2 eV, which isn't much in the grand scheme of things.

Ultimately, the limiting factor with most photodiodes is simply thermal dissipation. In your case, you are dissipating &lt; 5 mW on an area that is perhaps 4 mm^2, and the temperature rise will be negligible. The photon energy doesn't much matter for visible (and IR/UV) light; all that matters is the power density and thermal dissipation of the target (the photodiode).