Laser is a very thin beam of light which makes it very hard to detect. Generally speaking, your radar detector’s built-in laser detector will only alert when you’re being targeted. Except for very rare instances, it won’t go off if the officer is targeting someone else. (Additionally, given that laser is aimed at your grill and your radar detector is up on your windshield, it may not even alert when you’re the one being targeted. ) For this reason, you can’t reliably depend on getting any advanced warning and thus protection against laser the way you can with radar.
Instead of relying on a laser detector, a better tool is a laser jammer. This is a custom installed piece of hardware that not only detects when you’re being shot, but it also actively fires jamming pulses back at the police officer, preventing him from getting a reading until you slow down and disable your jammers.