Laser Cooling without Spontaneous Emission

Corder, Christopher; Arnold, Brian; Metcalf, Harold

doi:10.1103/physrevlett.114.043002

Cited by 40 publications

(41 citation statements)

References 16 publications

(27 reference statements)

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“…2 we conclude that the full width at half maximum of the beam distribution is reduced from 10.6±0.2 mm to 9.3±0.2 mm. In earlier experiments, both longitudinal [40] and transverse [41] cooling of atomic beams have been previously observed, including in the ultimate limit of 1 scattered photon [51]. In combination with previous atomic experiments [41], our results indicate the possibility of creating optical molasses-like bichromatic field configurations characterized by rapid damping forces and wide velocity capture range using two sequential spatially separated regions with opposite φ.…”

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confidence: 82%

Coherent Bichromatic Force Deflection of Molecules

et al. 2018

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We demonstrate the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retro-reflected laser beam addressing theX 2 Σ + ↔Ã 2 Π 1/2 electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counter propagating laser beams we reverse the direction of the applied force. A momentum transfer of 70 k is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.Laser manipulation of atomic motion has revolutionized atomic, molecular and optical (AMO) physics [1,2]. The widely-used techniques of laser cooling and trapping made possible the creation of ultracold degenerate quantum gases [3], simulation of important condensed matter models [4] and development of new quantum sensors [5,6] and clocks [7]. Laser deceleration and cooling of atomic beams -a necessary part of the trap loading process -typically requires scattering tens of thousands of photons in order to bring room (or oven) temperature atoms to velocities where they can be confined by electromagnetic traps for further studies [8]. While beam deceleration employing the spontaneous radiation pressure force has been a standard for atomic experiments, its application to slowing molecular beams has been limited by the small change in kinetic energy per scattered photon and the myriad of internal molecular states, which inhibits photon cycling. At the same time, there is extreme interest in creating ultracold molecules for new physics applications [9].Neutral diatomic molecules are predicted to play an important role in diverse research areas of modern physics such as quantum simulation [10] and computation [11], as well as searches for new particles and fields beyond the Standard Model [12]. Larger polyatomic molecules will provide additional opportunities in physics and chemistry [13][14][15]. For example, exploring the origin of biomolecular homochirality [16] and understanding primordial chemistry leading to the development of organic life requires the use of large molecules [17]. However, these molecules' complexity presents significant challenges for direct laser slowing and cooling. Yet these are the key ingredients that allow for optical trapping, which, in turn, realizes long moleculelaser coherence times and high levels of quantum state control. Previously, the external motion of gas-phase polyatomic molecules has been manipulated with off-resonant laser fields [18] as well as electric [19], magnetic [20], and mechanical techniques [21]. Inspired by the success of...

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supporting

confidence: 82%

Coherent Bichromatic Force Deflection of Molecules

et al. 2018

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“…From a fundamental perspective, this work has important implications for the ongoing discussion of the role of spontaneous emission in dissipating entropy during laser cooling [15,16]. Our view is that spontaneous emission (or another form of dissipation) is necessary to achieve phase-space compression, but that the total number of spontaneously scattered photons required can be quite low (of order one).…”

mentioning

confidence: 96%

Narrow-line laser cooling by adiabatic transfer

et al. 2018

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We propose and demonstrate a novel laser cooling mechanism applicable to particles with narrowlinewidth optical transitions. By sweeping the frequency of counter-propagating laser beams in a sawtooth manner, we cause adiabatic transfer back and forth between the ground state and a longlived optically excited state. The time-ordering of these adiabatic transfers is determined by Doppler shifts, which ensures that the associated photon recoils are in the opposite direction to the particle's motion. This ultimately leads to a robust cooling mechanism capable of exerting large forces via a weak transition and with reduced reliance on spontaneous emission. We present a simple intuitive model for the resulting frictional force, and directly demonstrate its efficacy for increasing the total phase-space density of an atomic ensemble. We rely on both simulation and experimental studies using the 7.5 kHz linewidth 1 S 0 to 3 P 1 transition in 88 Sr. The reduced reliance on spontaneous emission may allow this adiabatic sweep method to be a useful tool for cooling particles that lack closed cycling transitions, such as molecules.

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“…However, standard Doppler cooling is limited in both final temperature and maximum force by the linewidth Γ and wavelength λ ≡ 2π/k of the available optical transitions -properties that are provided by nature and not under control of the experimentalist. Understanding methods and limitations for removing entropy from a system is of fundamental interest and continues to be widely explored [13][14][15][16][17][18][19].…”

Section: Introduction To Swap Coolingmentioning

confidence: 99%

“…After each photon absorption event, a molecule needs to return to the initial state via spontaneous emission for Doppler cooling to work, but it may be lost instead due to the abundance of accessible vibrational and rotational degrees of freedom [20,21]. This challenge has motivated the development of alternative techniques that rely on reducing the role of spontaneous emission relative to Doppler cooling, including Sisyphus cooling of molecules [18,23], bichromatic force slowing and cooling [16,24], and interferometric cooling [19].…”

Section: Introduction To Swap Coolingmentioning

confidence: 99%

Laser cooling with adiabatic transfer on a Raman transition

Greve

Thompson

2019

New J. Phys.

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Sawtooth Wave Adiabatic Passage (SWAP) laser cooling was recently demonstrated using a narrowlinewidth single-photon optical transition in atomic strontium and may prove useful for cooling other atoms and molecules. However, many atoms and molecules lack the appropriate narrow optical transition. Here we use such an atom, 87 Rb, to demonstrate that two-photon Raman transitions with arbitrarily-tunable linewidths can be used to achieve 1D SWAP cooling without significantly populating the intermediate excited state. Unlike SWAP cooling on a narrow transition, Raman SWAP cooling allows for a final 1D temperature well below the Doppler cooling limit (here, 25 times lower); and the effective excited state decay rate can be modified in time, presenting another degree of freedom during the cooling process. We also develop a generic model for Raman Landau-Zener transitions in the presence of small residual free-space scattering for future applications of SWAP cooling in other atoms or molecules.

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Laser Cooling without Spontaneous Emission

Cited by 40 publications

References 16 publications

Coherent Bichromatic Force Deflection of Molecules

Coherent Bichromatic Force Deflection of Molecules

Narrow-line laser cooling by adiabatic transfer

Laser cooling with adiabatic transfer on a Raman transition

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