Yes, most cops use laser or radar "instant-on" detection nowadays. Back in the old days, the radar gun was always on. Radar detectors worked by picking up the residual radiation in advance, while the cop was targeting other cars before he targeted your car specifically. Now, even with radar, the guns have a narrow beam that the cop can pull the trigger and focus on one specific car, and they can get a speed reading in a split second (this is called "instant-on") with little to no residual radiation for other cars with detectors to pick up. He's writing the ticket before you can slam the brakes.
If you want a real way to cut down on tickets, that is free, take off your front license plate. This is illegal in most areas and can get you a ~$100 ticket (that won't show on your driving record). BUT, modern front license plates are specifically designed to make a perfect target to reflect police radar and laser guns. Otherwise, modern cars are generally too rounded and have too few reflective surfaces for the cop to get an accurate reading on. Oddly enough, the company that contracts to most states to make license plate materials and paints is the same company that makes most photo radar and red-light cameras and makes most police radar/laser guns (answer: Lockheed).