Dark optical trap

An optical trap is a configuration of light fields which captures neutral atoms due to their interaction with light. Traps using light with a frequency slightly lower than one of the atom’s resonance frequencies are called red detuned optical traps. Traps using light with a frequency slightly higher than one of the atom’s resonance frequencies are called blue detuned optical traps. A blue detuned optical trap is called a dark optical trap. Since red detuned light attracts atoms, and blue detuned light repels atoms, trapped atoms in a red detuned trap are exposed to light within the whole trapping region whereas trapped atoms in a blue detuned trap, being surrounded by repulsive light fields, are captured in regions without light, which means in the dark. This explains the name dark optical trap. Dark optical traps are suitable for the investigation of the dynamics of trapped atoms, since they yield minimal interaction between the atoms and the trapping light.