What’s Laser Locking?

In many photonics labs, the optical experiment will involve using laser beams to energize atoms or ions. In order for this interaction to be achieved successfully, the laser beam must possess a specific amount of energy that corresponds to the energy gap associated with a particular atomic transition. This energy is related to the frequency (or wavelength) of the laser. A higher frequency (or shorter wavelength) laser will correspond to higher energy, and vice versa. For a laser to successfully interact with the atom, it should produce light at a desired frequency, and keep steadily producing this frequency throughout the timeframe of the experiment. However, the set desired frequency is only an average, which means that the actual frequency can vary a lot within a wide range. This is where laser locking proves invaluable. Laser locking provides a means to stabilize the frequency of the laser with the frequency closer to the set point. Various methods exist for laser locking, with some popular techniques including saturated spectroscopy, offset phase lock (OPL), and dichroic atomic vapor laser lock (DAVLL). Some of these may be more applicable than others depending on the nature of the atomic transition.