Interesting thread.
The potential use of lasers for personal defense deserves some careful consideration (at least here in the US where criminals seem to be able to sue their victims for defending themselves against their unlawful actions, thus eventually robbing them of their rights and property "legally"!
But I digress.)
I like the idea of a "Personal Defense Laser".
In my opinion,
I think the use of brilliant light (at night especially) to distract or temporarily disable a criminal is a viable defense option. Lasers being the brightest sources are automatic contenders. Two advantages immediately come to mind. One being the ability to put the light right where one wants it - in the attacker's eyes (and not also in your own in the case of flashlamps or other flash devices), and another being that 100% of the delivered power is concentrated in a region of the spectrum (green/blue) that is
most effective for trashing night vision. The main problem lies with the coherency of unaltered laser light; if the beam enters the eye and is focused, very small images are formed at high energy density which can damage the retina. Severe blinding without damage is the goal here.
Perhaps an ideal "PDL" could be designed to reduce the coherency, by using a holographic grating similar to the ones used to generate patterns, at the same time producing a large diameter beam (or a very tight cone) of light. This would make hitting the attacker's eyes easier in a panic situation while maintaining the needed intensity, while greatly reducing or eliminating the potential for retinal damage (and possible subsequent lawsuits).
Thoughts?