Described in this article and in this wiki.. This works by irradiating the surface layer of human skin so that intense heat based pain is generated. It’s basically cooking you.
As a battlefield weapon maybe, but crowd control? Really? The potential for permanent harm looms huge. Little kids get in the way? Cooking your eyeballs? If you fall and can’t move and it continues to cook you? You have piercings and you will get charred at the point where they touch flesh? The liability would seem to be insane.
What kind of liability insurance would a police dept have to have to implement this?
Most crowd/riot control options have a potential for harm - tear gas and pepper spray, for example, can trigger asthmatic reactions with the usual risks of harm and death for severe cases. Rubber bullets can blind and sometimes kill. And so on.
It sounds like you didn’t read your own link. The beam appears to be painful, but doesn’t penetrate the skin deep enough to actually “cook” you.
Although it would also appear to make tinfoil hats an actual practical countermeasure.
I read the link - if you keep the beam on a person long enough it seems like it could cause at least second degree burns (pea-sized blisters were mentioned) and people who physically can’t move out of the way, like infants, the disabled, etc. are at risk of such a thing.
So… the actions of the operator are a factor. If you had a sadist or an incompetent I could see people getting burned.