View source for Physics:Laser cooling

{{Short description|Class of methods for cooling atoms to very low temperatures}}
[[File:Doppler laser cooling.svg|thumb|upright|200px|Simplified principle of Doppler laser cooling:
{|
!valign="top"|1
|A stationary atom sees the laser neither red- nor blue-shifted and does not absorb the photon.
|-
!valign="top"|2
|An atom moving away from the laser sees it red-shifted and does not absorb the photon.
|-
!valign="top"|31
|An atom moving towards the laser sees it blue-shifted and absorbs the photon, slowing the atom.
|--
!valign="top"|32
|The photon excites the atom, moving an electron to a higher quantum state.
|--
!valign="top"|33
|The atom re-emits a photon but in a random direction. The atom momentum vectors would add to the original if they were in the same direction but they are not so the atom has lost energy and, therefore, cooled.
|}]]

'''Laser cooling''' includes a number of techniques where [[Physics:Atom|atom]]s, [[Physics:Molecule|molecule]]s, and small mechanical systems are cooled with laser light.  The directed energy of lasers is often associated with heating materials, e.g. [[Physics:Laser cutting|laser cutting]], so it can be counterintuitive that laser cooling often results in sample [[Physics:Temperature|temperature]]s approaching  [[Physics:Absolute zero|absolute zero]]. [[Physics:Laser|Laser]] cooling relies on the change in momentum when an object, such as an atom, absorbs and re-emits a [[Physics:Photon|photon]] (a particle of light).  For example, if laser light illuminates a warm cloud of atoms from all directions and the laser's frequency is tuned below an atomic resonance, the atoms will be cooled.  This common type of laser cooling relies on the [[Physics:Doppler effect|Doppler effect]] where individual atoms will preferentially absorb laser light from the direction opposite to the atom's motion.  The absorbed light is re-emitted by the atom in a random direction. After repeated emission and absorption of light the net effect on the cloud of atoms is that they will expand more slowly.  The slower expansion reflects a decrease in the velocity distribution of the atoms, which corresponds to a lower temperature and therefore the atoms have been cooled.  For an ensemble of particles, their [[Physics:Thermodynamic temperature|thermodynamic temperature]] is proportional to the [[Variance|variance]] in their velocity. More homogeneous velocities between particles corresponds to a lower temperature. Laser cooling techniques combine [[Physics:Atomic spectroscopy|atomic spectroscopy]] with the aforementioned mechanical effect of light to compress the velocity distribution of an ensemble of particles, thereby cooling the particles.

The 1997 Nobel Prize in Physics was awarded to [[Biography:Claude Cohen-Tannoudji|Claude Cohen-Tannoudji]], [[Biography:Steven Chu|Steven Chu]], and [[Biography:William Daniel Phillips|William Daniel Phillips]] "for development of methods to cool and trap atoms with laser light".<ref>{{cite web | title = The Nobel Prize in Physics 1997 | publisher = Nobel Foundation | url = http://nobelprize.org/nobel_prizes/physics/laureates/1997/index.html | access-date = 9 October 2008 | archive-url = https://web.archive.org/web/20081007171154/http://nobelprize.org/nobel_prizes/physics/laureates/1997/index.html | archive-date = 7 October 2008 | url-status = live }}</ref>

== History ==

=== Radiation pressure ===
[[Astronomy:Radiation pressure|Radiation pressure]] is the force that electromagnetic radiation exerts on matter.  In 1873 Maxwell published his treatise on [[Physics:Electromagnetism|electromagnetism]] in which he predicted radiation pressure.<ref name="Maxwell1873">
{{cite book| title=A Treatise on Electricity and Magnetism (1st edition), II.| first=J.C.| last=Maxwell| year=1873| location=Oxford| pages=391}}
</ref>  The force was experimentally demonstrated for the first time by [[Biography:Pyotr Lebedev|Lebedev]] and reported at a conference in Paris in 1900,<ref name="Lebedev1900">
{{cite conference| url=https://www.europhysicsnews.org/articles/epn/pdf/2019/04/epn2019504p15.pdf| title=Les forces de Maxwell-Bartoli dues à la pression de la lumière| first=Pyotr| last=Lebedew| year=1900| conference=Rapports présentés au Congrès International de Physique | volume=2| location=Paris| pages=133}}
</ref> and later published in more detail in 1901.<ref name="Lebedew1901">
{{cite journal
 |last=Lebedew |first=P.
 |year=1901
 |title=Untersuchungen über die Druckkräfte des Lichtes
 |journal=[[Physics:Annalen der Physik|Annalen der Physik]]
 |volume=311 |issue=11 |pages=433–458
 |bibcode=1901AnP...311..433L
 |doi=10.1002/andp.19013111102
|url=https://zenodo.org/record/1424005
 }}</ref>   Following Lebedev's measurements Nichols and [[Biography:Gordon Ferrie Hull|Hull]] also demonstrated the force of radiation pressure in 1901,<ref name="Nichols1901">
{{Cite journal|last1=Nichols |first1=E.F. |last2=Hull |first2=G.F. |title=A Preliminary Communication on the Pressure of Heat and Light Radiation|url=https://link.aps.org/doi/10.1103/PhysRevSeriesI.13.307|journal=Physical Review |series=Series I |doi=10.1103/PhysRevSeriesI.13.307 |year=1901|volume=13 |issue=5 |pages=307–320 |bibcode=1901PhRvI..13..307N }}
</ref> with a refined measurement reported in 1903.<ref name="Nichols1">
{{Cite journal|last=Nichols and Hull|first=E.F. and G.F.|title=The Pressure Due To Radiation . (Second Paper.) <!--DUPLICATE|url=http://massey.dur.ac.uk/articles/newoptics.pdf--> | year=1903 | pages=26–50| volume=17 | url=https://journals.aps.org/pri/abstract/10.1103/PhysRevSeriesI.17.26| journal=Physical Review|issue=1 |doi=10.1103/PhysRevSeriesI.17.26 |bibcode=1903PhRvI..17...26N }}
</ref>
<ref name="Nichols2">
{{Cite journal|last=Nichols and Hull|first=E.F. and G.F.|title=The Pressure Due To Radiation. (Second Paper.) <!--DUPLICATE|url=http://massey.dur.ac.uk/articles/newoptics.pdf--> | year=1903 | pages=91–104| volume=17 | url=https://journals.aps.org/pri/abstract/10.1103/PhysRevSeriesI.17.91| journal=Physical Review|issue=2 |doi=10.1103/PhysRevSeriesI.17.91 |bibcode=1903PhRvI..17...91N }}
</ref> 

In 1933, Otto Frisch deflected an atomic beam of sodium atoms with light.  
<ref name="Frisch">
{{Cite journal|last=Frisch|first=R. |title= Experimenteller Nachweis des Einsteinschen Strahlungsrückstoßes |url=https://link.springer.com/article/10.1007/BF01340182| year=1933 | pages=42–48| volume=86 | journal=Zeitschrift für Physik|issue=1–2 |doi=10.1007/BF01340182 |bibcode=1933ZPhy...86...42F |s2cid=123038196 }}
</ref> 
This was the first realization of radiation pressure acting on a resonant absorber.

=== Laser cooling proposals ===
The introduction of [[Physics:Laser|laser]]s in atomic manipulation experiments was the precursor to the laser cooling proposals in the mid 1970s. Laser cooling was proposed separately in 1975 by two different research groups: [[Biography:Theodor W. Hänsch|Hänsch]] and [[Biography:Arthur Leonard Schawlow|Schawlow]],
<ref name="Hänsch1975">{{cite journal |last1=Hänsch |first1=T. W. |last2=Schawlow |first2=A. L. |title=Cooling of gases by laser radiation |journal=Optics Communications |date=January 1975 |volume=13 |issue=1 |pages=68–69 |doi=10.1016/0030-4018(75)90159-5|doi-access=free }}</ref> and Wineland and [[Biography:Hans Georg Dehmelt|Dehmelt]].<ref>{{cite journal |last1=Wineland |first1=David |last2=Dehmelt |first2=Hans |title=Proposed 1014 delta upsilon less than upsilon laser fluorescence spectroscopy on t1+ mono-ion oscillator iii |journal=Bulletin of the American Physical Society |date=January 1, 1975 |volume=20 |issue=4 |page=637}}</ref> Both proposals outlined the simplest laser cooling process, known as [[Physics:Doppler cooling|Doppler cooling]], where laser light below an atom's resonant frequency is repeatedly absorbed and the velocity distribution of the atoms is reduced.<ref name=":0">{{Cite journal|last=Phillips|first=William D.|title=Nobel Lecture: Laser cooling and trapping of neutral atoms|journal=Reviews of Modern Physics|volume=70|issue=3|pages=721–741|doi=10.1103/revmodphys.70.721|bibcode=1998RvMP...70..721P|year=1998|doi-access=free}}</ref> 

In 1977  [[Biography:Arthur Ashkin|Ashkin]] submitted a paper which describes how Doppler cooling could be used to provide the necessary damping to load atoms into an optical trap.<ref>{{cite journal |last1=Ashkin |first1=A. |title=Trapping of Atoms by Resonance Radiation Pressure |journal=Physical Review Letters |date=20 March 1978 |volume=40 |issue=12 |pages=729–732 |doi=10.1103/PhysRevLett.40.729}}</ref>  In this work he emphasized how this process could allow for long [[Physics:Spectroscopy|spectroscopic]] measurements without the atoms escaping the trap and proposed the overlapping of [[Physics:Optics|optical]] traps in order to study interactions between different atoms.

=== Initial realizations ===
Following the laser cooling proposals, in 1978 two research groups that Wineland, Drullinger and Walls of NIST, and Neuhauser, Hohenstatt, Toscheck and Dehmelt of the University of Washington succeeded in laser cooling atoms. The NIST group wanted to reduce the effect of Doppler broadening on spectroscopy. They cooled magnesium ions in a Penning trap to < 40 Kelvin.  The Washington group cooled barium ions. 
The research from both groups served to illustrate the mechanical properties of light.<ref name=":0" /> Around this time, laser cooling techniques had allowed for temperatures lowered to around 40 [[Kelvin|kelvin]]s.

Influenced by the Wineland's work on laser cooling ions, [[Biography:William Daniel Phillips|William Phillips]] applied the same principles to laser cool neutral atoms. In 1982, he published the first paper where neutral atoms were laser cooled.<ref>{{cite journal |last1=Phillips |first1=William |title=Laser Deceleration of an Atomic Beam |journal=Physical Review Letters |date=1 March 1982 |volume=48 |issue=9 |pages=596–599 |doi=10.1103/PhysRevLett.48.596 |bibcode=1982PhRvL..48..596P |doi-access=free }}</ref> The process used is now known as the [[Physics:Zeeman slower|Zeeman slower]] and is a standard technique for slowing an atomic beam.

=== Modern advances ===

==== Atoms ====
[[File:First Laser Cooling.png|thumbnail|left|Cumulative number of unique atoms/isotopes laser cooled vs year.]]

The Doppler cooling limit for electric dipole transitions is typically in the hundreds of microkelvins. In the 1980s this limit was seen as the lowest achievable temperature. It was a surprise then when sodium atoms were cooled to 43 microkelvin when their Doppler cooling limit is 240 microkelvin,<ref>{{cite journal |author1=Paul D. Lett |author2= Richard N. Watts |author3=Christoph I. Westbrook |author4= William D. Phillips |author5=A. Winnicki |author6= Phillip L. Gould |author7= Harold J. Metcalf | title=Observation of Atoms Laser Cooled below the Doppler Limit | journal= Physical Review Letters| year=1988 |volume= 61 |issue= 2 |pages= 169–172 | doi=10.1103/PhysRevLett.61.169|pmid= 10039050 |bibcode= 1988PhRvL..61..169L |s2cid= 8479501 |doi-access= free }}</ref> the new low was explained by the addition of more atomic states in combination to laser polarization. Previous conceptions of laser cooling were decided to have been too simplistic.<ref name=":1">{{Cite journal|last=Bardi|first=Jason Socrates|date=2008-04-02|title=Focus: Landmarks: Laser Cooling of Atoms|url=https://physics.aps.org/story/v21/st11|journal=Physics|language=en-US|volume=21|page=11 |doi=10.1103/physrevfocus.21.11}}</ref> The major laser cooling breakthroughs in the 70s and 80s led to several improvements to preexisting technology and new discoveries with temperatures just above [[Physics:Absolute zero|absolute zero]]. The cooling processes were utilized to make [[Engineering:Atomic clock|atomic clock]]s more accurate and to improve spectroscopic measurements, and led to the observation of a new [[Physics:State of matter|state of matter]] at ultracold temperatures.<ref name=":2">{{Cite journal|last=Adams and Riis|first=Charles S. and Erling|title=Laser Cooling and Manipulation of Neutral Particles|url=http://massey.dur.ac.uk/articles/newoptics.pdf|journal=New Optics|access-date=2017-05-06|archive-date=2017-11-15|archive-url=https://web.archive.org/web/20171115193505/http://massey.dur.ac.uk/articles/newoptics.pdf|url-status=dead}}</ref><ref name=":1" /> The new state of matter, the [[Physics:Bose–Einstein condensate|Bose–Einstein condensate]], was observed in 1995 by [[Biography:Eric Allin Cornell|Eric Cornell]], [[Biography:Carl Wieman|Carl Wieman]], and [[Biography:Wolfgang Ketterle|Wolfgang Ketterle]].<ref>{{cite journal |last1=Chin |first1=Cheng |title=Ultracold atomic gases going strong |journal=National Science Review |date=1 June 2016 |volume=3 |issue=2 |pages=168–170 |doi=10.1093/nsr/nwv073 |doi-access=free }}</ref>

Laser cooling was primarily used to create ultracold atoms. For example, the experiments in quantum physics need to perform near [[Physics:Absolute zero|absolute zero]] where unique quantum effects such as Bose–Einstein condensation can be observed.  Laser cooling is also a primary tool in optical clock experiments.

==== Molecules ====
In 2010, a team at Yale successfully laser-cooled a [[Chemistry:Diatomic molecule|diatomic molecule]].<ref>{{cite journal |author1=E. S. Shuman |author2=J. F. Barry |author3=D. DeMille | title=Laser cooling of a diatomic molecule | journal=Nature | year=2010 | volume=467 |issue=7317 | pages=820–823 | doi=10.1038/nature09443 | pmid=20852614|arxiv = 1103.6004 |bibcode = 2010Natur.467..820S |s2cid=4430586 }}</ref> In 2016, a group at MPQ successfully cooled [[Physics:Formaldehyde|formaldehyde]] to 420&nbsp;μK via optoelectric Sisyphus cooling.<ref>{{cite journal |last1=Prehn |first1=Alexander |last2=Ibrügger |first2=Martin |last3=Glöckner |first3=Rosa |last4=Rempe |first4=Gerhard |last5=Zeppenfeld |first5=Martin |title=Optoelectrical Cooling of Polar Molecules to Submillikelvin Temperatures |journal=Physical Review Letters |date=10 February 2016 |volume=116 |issue=6 |pages=063005 |doi=10.1103/PhysRevLett.116.063005 |url=https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.063005 |access-date=10 January 2024|arxiv=1511.09427 }}</ref> In 2022, a group at Harvard successfully laser cooled and trapped CaOH to 720(40)&nbsp;μK in a [[Physics:Magneto-optical trap|magneto-optical trap]].<ref>{{cite journal |author1=N. B. Vilas |author2= C. Hallas |author3=L. Anderegg |author4=P. Robichaud |author5=A. Winnicki |author6=D. Mitra |author7=J. M. Doyle | title=Magneto-optical trapping and sub-Doppler cooling of a polyatomic molecule | journal=Nature | year=2022 |volume= 606 |issue= 7912 |pages= 70–74 | doi=10.1038/s41586-022-04620-5 |pmid= 35650357 | arxiv = 2112.08349v1 |bibcode= 2022Natur.606...70V |s2cid= 245144894 }}</ref>

==== Mechanical systems ====
In 2007, an MIT team  successfully laser-cooled a macro-scale (1 gram) object to 0.8 K.<ref>{{cite news |title=Laser-cooling Brings Large Object Near Absolute Zero |url=https://www.sciencedaily.com/releases/2007/04/070406171036.htm |work=ScienceDaily }}</ref> In 2011, a team from the California Institute of Technology and the University of Vienna became the first to laser-cool a (10 μm x 1 μm) mechanical object to its quantum ground state.<ref>[https://www.caltech.edu/about/news/caltech-team-uses-laser-light-cool-object-quantum-ground-state-1726 Caltech Team Uses Laser Light to Cool Object to Quantum Ground State]. Caltech.edu. Retrieved June 27, 2013. Updated 10/05/2011</ref>

== Methods ==

The first example of laser cooling, and also still the most common method (so much so that it is still often referred to simply as 'laser cooling') is [[Physics:Doppler cooling|Doppler cooling]]. 

=== Doppler cooling ===
{{main|Physics:Doppler cooling}}
[[File:Rubidium85 laser cooling.png|thumbnail|left|The lasers needed for the magneto-optical trapping of rubidium-85: (a) & (b) show the absorption (red detuned to the dotted line) and spontaneous emission cycle, (c) & (d) are forbidden transitions, (e) shows that if a cooling laser excites an atom to the ''F''=3 state, it is allowed to decay to the "dark" lower hyperfine, ''F''=2 state, which would stop the cooling process, if it were not for the repumper laser (f).]]
Doppler cooling, which is usually accompanied by a magnetic trapping force to give a [[Physics:Magneto-optical trap|magneto-optical trap]], is by far the most common method of laser cooling. It is used to cool low density gases down to the [[Physics:Doppler cooling limit|Doppler cooling limit]], which for [[Chemistry:Rubidium|rubidium]]-85 is around 150 microkelvins.

In Doppler cooling, initially, the frequency of light is tuned slightly below an electronic transition in the [[Physics:Atom|atom]]. Because the light is [[Physics:Laser detuning|detuned]] to the "red" (i.e.,&nbsp;at lower frequency) of the transition, the atoms will absorb more [[Physics:Photon|photon]]s if they move towards the light source, due to the [[Physics:Doppler effect|Doppler effect]]. Thus if one applies light from two opposite directions, the atoms will always scatter more photons from the laser beam pointing opposite to their direction of motion. In each scattering event the atom loses a [[Physics:Momentum|momentum]] equal to the momentum of the photon. If the atom, which is now in the excited state, then emits a photon spontaneously, it will be kicked by the same amount of momentum, but in a random direction. Since the initial momentum change is a pure loss (opposing the direction of motion), while the subsequent change is random, the probable result of the absorption and emission process is to reduce the momentum of the atom, and therefore its [[Physics:Speed|speed]]&mdash;provided its initial speed was larger than the recoil speed from scattering a single photon. If the absorption and emission are repeated many times, the average speed, and therefore the [[Physics:Kinetic energy|kinetic energy]] of the atom, will be reduced. Since the [[Physics:Temperature|temperature]] of a group of atoms is a measure of the average random internal kinetic energy, this is equivalent to cooling the atoms.

=== Anti-Stokes cooling ===

The idea for anti-Stokes cooling was first advanced by Pringsheim in 1929.<ref>P. Pringsheim (1929). {{cite news |title=Zwei Bemerkungen über den Unterschied von Lumineszenz- und Temperaturstrahlung |url=https://link.springer.com/article/10.1007/BF01340652 |work=Zeitschrift für Physik |year=1929 |doi=10.1007/BF01340652 |last1=Pringsheim |first1=Peter |volume=57 |issue=11–12 |pages=739–746 }}</ref>  While Doppler cooling lowers the translational temperature of a sample, anti-Stokes cooling decreases the vibrational or phonon excitation of a medium.  This is accomplished by pumping a substance with a laser beam from a low-lying energy state to a higher one with subsequent emission to an even lower-lying energy state.  The principal condition for efficient cooling is that the anti-Stokes emission rate to the final state be significantly larger than that to other states as well as the nonradiative relaxation rate.  Because vibrational or phonon energy can be many orders of magnitude larger than the energy associated with Doppler broadening, the efficiency of heat removal per laser photon expended for anti-Stokes cooling can be correspondingly larger than that for Doppler cooling.  The anti-Stokes cooling effect was first demonstrated by Djeu and Whitney in CO<sub>2</sub> gas.<ref>N. Djeu and W.T. Whitney (1981) {{cite news |title=Laser cooling by spontaneous anti-Stokes scattering |url=https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.46.236 |work=Physical Review Letters|year=1981 |doi=10.1103/PhysRevLett.46.236 |last1=Djeu |first1=N. |last2=Whitney |first2=W. T. |volume=46 |issue=4 |pages=236–239 }}</ref> The first anti-Stokes cooling in a solid was demonstrated by Epstein et al. in 1980, in a ytterbium doped fluoride glass sample.<ref>R.I. Epstein, M.I. Buchwald, B.C. Edwards, T.R. Gosnell, and C.E. Mungan (1995) {{cite news |title=Observation of laser-induced fluorescent cooling of a solid |url=https://www.nature.com/articles/377500a0 |work=Nature }}</ref>

Potential practical applications for anti-Stokes cooling of solids include radiation balanced solid state lasers and vibration-free optical refrigeration.<ref>S.R. Bowman (1999) {{cite news |title=Lasers without internal heat generation |url=https://ieeexplore.ieee.org/document/737628 |work=IEEE Journal of Quantum Elect |year=1999 |doi=10.1109/3.737628 |last1=Bowman |first1=S.R. |volume=35 |pages=115–122 }}</ref><ref>D.V. Seletskiy, R. Epstein, and M. Sheik-Bahae (2016) {{cite news |title=Laser cooling in solids: advances and prospects |url=https://iopscience.iop.org/article/10.1088/0034-4885/79/9/096401/meta |work=Reports on Progress in Physics |year=2016 |doi=10.1088/0034-4885/79/9/096401 |last1=Seletskiy |first1=Denis V. |last2=Epstein |first2=Richard |last3=Sheik-Bahae |first3=Mansoor |volume=79 |issue=9 |page=096401 }}</ref>

=== Other methods ===
Other methods of laser cooling include:
* [[Physics:Sisyphus cooling|Sisyphus cooling]]<ref>[https://www.nobelprize.org/uploads/2018/06/phillips-lecture.pdf Laser cooling and trapping of neutral atoms] Nobel Lecture by [[Biography:William Daniel Phillips|William D. Phillips]], Dec 8, 1997: {{cite journal | doi = 10.1103/RevModPhys.70.721 | bibcode=1998RvMP...70..721P | volume=70 | title=Nobel Lecture: Laser cooling and trapping of neutral atoms | year=1998 | journal=Reviews of Modern Physics | pages=721–741 | last1 = Phillips | first1 = William D.| issue=3 | doi-access=free }}</ref>
* [[Physics:Resolved sideband cooling|Resolved sideband cooling]]
* [[Physics:Raman cooling|Raman sideband cooling]]
* Velocity selective coherent population trapping (VSCPT)<ref>{{cite journal |author1=A. Aspect |author2=E. Arimondo |author3=R. Kaiser |author4=N. Vansteenkiste |author5=C. Cohen-Tannoudji | title=Laser Cooling below the One-Photon Recoil Energy by Velocity-Selective Coherent Population Trapping | journal=Physical Review Letters | year=1988 | volume=61 |issue=7 | pages=826–829 | doi=10.1103/PhysRevLett.61.826 |pmid=10039440 | bibcode=1988PhRvL..61..826A|doi-access=free }}</ref>
* [[Physics:Gray molasses|Gray molasses]]
* [[Physics:Optical molasses|Optical molasses]]
* Cavity-mediated cooling<ref>{{cite journal |author1=Peter Horak |author2=Gerald Hechenblaikner |author3=Klaus M. Gheri |author4=Herwig Stecher |author5=Helmut Ritsch | title=Cavity-Induced Atom Cooling in the Strong Coupling Regime | journal=Physical Review Letters | year=1988 | volume=79 |issue=25 | pages=4974–4977 | doi=10.1103/PhysRevLett.79.4974 | bibcode=1997PhRvL..79.4974H}}</ref>
* Use of a [[Physics:Zeeman slower|Zeeman slower]]
* [[Physics:Electromagnetically induced transparency|Electromagnetically induced transparency (EIT)]] cooling<ref>{{Cite journal|title = Single-atom imaging of fermions in a quantum-gas microscope|journal = Nature Physics|pages = 738–742|volume = 11|issue = 9|doi = 10.1038/nphys3403|first1 = Elmar|last1 = Haller|first2 = James|last2 = Hudson|first3 = Andrew|last3 = Kelly|first4 = Dylan A.|last4 = Cotta|first5 = Bruno|last5 = Peaudecerf|first6 = Graham D.|last6 = Bruce|first7 = Stefan|last7 = Kuhr|arxiv = 1503.02005 |bibcode = 2015NatPh..11..738H |year = 2015|s2cid = 51991496}}</ref>
* Anti-Stokes cooling in solids
* [[Physics:Polarization gradient cooling|Polarization gradient cooling]]

==See also==
* {{annotated link|Physics:List of laser articles}}
* {{annotated link|Biology:Optical tweezers}}
* {{annotated link|Physics:Zeeman slower|Zeeman Slower}}
* {{annotated link|Physics:Mössbauer effect}}
* {{annotated link|Mössbauer spectroscopy}}
* {{annotated link|Engineering:Timeline of low-temperature technology}}
* [[Physics:Particle beam cooling|Particle beam cooling]]

==References==
{{Reflist}}

==Additional sources==
* {{cite book |last1=Foot |first1=C. J. |title=Atomic Physics |date=2005 |publisher=Oxford University Press |isbn=978-0-19-850695-9 }}
* {{cite book |doi=10.1142/6631 |title=Advances in Atomic Physics |year=2011 |last1=Cohen-Tannoudji |first1=Claude |last2=Guéry-Odelin |first2=David |isbn=978-981-277-496-5 }}
* {{cite web|last=Bowley|first=Roger|title=Laser Cooling|url=http://www.sixtysymbols.com/videos/lasercooling.htm|work=Sixty Symbols|publisher=[[Biography:Brady Haran|Brady Haran]] for the [[Organization:University of Nottingham|University of Nottingham]]|author2=Copeland, Ed |year=2010}}
* [http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lascool.html Laser Cooling] HyperPhysics
* PhysicsWorld series of articles by [[Biography:Chad Orzel|Chad Orzel]]:
** [https://physicsworld.com/a/cold-how-physicists-learned-to-manipulate-and-move-particles-with-laser-cooling/ Cold: how physicists learned to manipulate and move particles with laser cooling]
** [https://physicsworld.com/a/colder-how-physicists-beat-the-theoretical-limit-for-laser-cooling-and-laid-the-foundations-for-a-quantum-revolution/ Colder: how physicists beat the theoretical limit for laser cooling and laid the foundations for a quantum revolution]
** [https://physicsworld.com/a/coldest-how-a-letter-to-einstein-and-advances-in-laser-cooling-technology-led-physicists-to-new-quantum-states-of-matter/ Coldest: how a letter to Einstein and advances in laser-cooling technology led physicists to new quantum states of matter]

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