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The concept of laser detuning emerged in tandem with formative experiments in laser physics. One of the earliest examples of high-impact work demonstrating the practical uses of laser detuning was Arthur Ashkin’s research in the 1970s, resulting in the first optical trapping demonstrations for which he was awarded the 2018 Nobel Prize in Physics. [3]
By detuning a laser beam to a frequency less than the resonant frequency (also known as red detuning), laser light is only absorbed if the light is frequency up-shifted by the Doppler effect, which occurs whenever the atom is moving towards the laser source. This applies a friction force to the atom whenever it moves towards a laser source.
Detuning can refer to: Musical tuning, the act of tuning an instrument or voice; Engine tuning, detuning one aspect, such as power, in favor of another aspect such as economy; Laser detuning, the difference between a laser frequency and a resonant frequency
Negative detuning (red detuning of the laser from the cavity resonance) by an amount equal to the mechanical mode frequency favors the anti-Stokes sideband and leads to a net cooling of the resonator. Laser photons absorb energy from the mechanical oscillator by annihilating phonons in order to become resonant with the cavity.
Optical molasses schematic. Optical molasses is a laser cooling technique that can cool neutral atoms to as low as a few microkelvins, depending on the atomic species. An optical molasses consists of 3 pairs of counter-propagating orthogonally polarized laser beams intersecting in the region where the atoms are present.
Ray optics explanation (focused laser). In addition to keeping the bead in the center of the laser, a focused laser also keeps the bead in a fixed axial position: The momentum change of the focused rays causes a force towards the laser focus, both when the bead is in front (left image) or behind (right image) the laser focus.
Doppler cooling involves light with frequency tuned slightly below an electronic transition in an atom.Because the light is detuned to the "red" (i.e. at lower frequency) of the transition, the atoms will absorb more photons if they move towards the light source, due to the Doppler effect.
Resolved sideband cooling is a laser-cooling technique that can be used to cool strongly trapped atoms to the quantum ground state of their motion. The atoms are usually precooled using the Doppler laser cooling. Subsequently, the resolved sideband cooling is used to cool the atoms beyond the Doppler cooling limit.