They use lasers in movies because it looks cool. Real beam-break detectors use regular light. Usually infrared so the source is invisible but it is still not a laser.
You don't even need especially fast sensors either. If the analog output reaches the low-light threshold hundreds of nanoseconds 'late' then it will be the same for both sensors and the speed calculation is unaffected.
Keep googling. This is a pretty common type of thing that the Arduino is good at.