Laser detuning

In optical physics, laser detuning is the tuning of a laser to a frequency that is slightly off from a quantum system's resonant frequency. Lasers can be detuned in the lab frame so that they are Doppler shifted to the resonant frequency in a moving system, which allows lasers to affect only atoms moving at a specific speed or in a specific direction and makes laser detuning a central tool of laser cooling and magneto-optical traps. Lasers tuned to a frequency below the resonant frequency are called red-detuned, and lasers tuned above resonance are called blue-detuned.