Beyond jamming, I imagine some kind of autonomous laser system could also be pretty effective at downing large numbers of drones within a given radius.
Lasers aren't effective. Most of the drone is just an empty frame. The control board is pretty tiny, as is the ordnance. Targeting those or the propulsion systems is quite difficult. Sure, you can punch holes in the chassis but it takes a lot of guesswork to hit something vital. It's the wrong weapon. Something with an area of effect, like a shotgun or a net is much better suited to stopping drones.
Having a laser that spreads out to e.g. 30cm radius at 500m is not hard to do if you need an area of effect weapon & can push enough power (ie. your laser is powerful enough, but not so intense that it ionizes the air & blocks itself). Reflections seem like a bigger problem: If the most effective defense includes guys with shotguns &/or there are a lot of unprotected personnel in the area, how do you make sure stray reflections don't end up blinding them?