Laser transmits an invisible light beam at a frequency (actually it transmits a "Wavelength") of 905 nanometers. A nanometer is how a light wavelength is measured. Same idea applies to a TV signal or radio signal. These signals are measured in hertz - megahertz to be precise.
Since laser guns use a specific light frequency or wavelength, it is possible to detect a laser's signature light pulse rates. Different laser guns operate at different light pulse rates. Some competitors call them "bands". All Whistler radar/laser detectors receive all current laser guns in use.
Keep in mind that laser detectors act differently than radar detectors. Since the narrow laser beam produces very little "scatter"- random bits of electromagnetic energy bouncing down the road -it is much harder to detect than a powerful radar gun that blankets the countryside with easily detectable microwave signals. Laser guns operate exclusively in instant-on mode and usually target vehicles at short range. Similar to instant on radar, if you are the target vehicle don't expect much warning. The result is your laser detector usually will offer less advance warning because at 1000 feet the beam is only 3 feet wide and that the officer aims at your license plate or headlights. The distance from where your detector is mounted to the license plate can be greater than 3 feet. This will be outside of the laser beam. If the officer is not steady while targeting vehicles, scatter laser signals can result, giving a possible signal to detect.