Recoil-Free Spectroscopy of Neutral Sr Atoms in the Lamb-Dicke Regime

Abstract

We have demonstrated a recoil-free spectroscopy on the 1 S0 − 3 P1 transition of strontium atoms confined in a one-dimensional optical lattice. By investigating the wavelength and polarization dependence of the ac Stark shift acting on the 1 S0 and 3 P1(mJ = 0) states, we determined the magic wavelength where the Stark shifts for both states coincide. The Lamb-Dicke confinement provided by this Stark-free optical lattice enabled the measurement of the atomic spectrum free from Doppler as well as recoil shifts.PACS numbers: 32.80. Pj, 32.30.Jc, 32.60.+i, 32.70.Jz Recent dramatic advances in optical metrology have made it possible to directly link two optical frequencies with an uncertainty below 10 −18 [1] and to coherently divide an optical frequency down to a radio frequency defined by the SI second [2]. Owing to these techniques, a stringent comparison of the stability and accuracy among optical clocks becomes feasible [3] and leads to an improved definition of time and a test of the time variation of a fundamental constant [4]. Up to now, two sorts of absorbers, single ions in the Lamb-Dicke regime (LDR) [5] and neutral atoms in free space, have been extensively studied for optical clocks. Tightly confined single ions, enabling a long interaction time and the Doppler-as well as the recoil-free absorption [6], have, so far, led to the narrowest optical spectrum [7]. However, the stability was severely limited by the quantum projection noise (QPN) [8] of the single absorber. The ensemble of neutral atoms, in contrast, provides a far better QPN limit. The accuracy of the measurement is known to be affected by the atomic motion, as residual Doppler shifts are introduced through the imperfect wave front of the probe beam [9,10].These two approaches could merge if an ensemble of neutral atoms were separately prepared in the LDR. An optical lattice made by the interference pattern of a light field [11] confines atoms in a small volume, which satisfies the Lamb-Dicke condition [5]. However, an impediment for the precision measurement is the complete control over the perturbations caused by this container, since the Stark shift potential strongly depends on the electronic state, which is not the case for ion-trapping potential.The transition frequency between the states, |g and |e , subjected to the ac Stark shift of the trap laser with * Current address: JILA, University of Colorado, CO 80309-0440.† Author to whom correspondence should be addressed. E-mail address: katori@amo.t.u-tokyo.ac.jp an electric field of E(ω L ,ǫ), can be written as,Here, ω e −ω g (= ω 0 ) is the unperturbed atomic resonance frequency, anddenotes the differential dipole-polarizability. If the polarizabilities α e and α g coincide at a specific trapping laser frequency ω L and polarizationǫ, the second term of Eq. (1) vanishes. Therefore, the unperturbed atomic transition frequency, independent of the trapping laser intensity of I L ∝ | E| 2 , can be observed [12,13]. This Stark shift cancellation technique was first demonstrated by an impr...

Strong coupling on a forbidden transition in strontium and nondestructive atom counting

“…We estimate that inhomogeneous transition broadening from the magic wavelength lattice is at most 44 kHz rms [37]. Since the inhomogeneous broadening is much less than Ω, its impact on the dressed modes is negligible [38].…”

Line shapes of optical Feshbach resonances near the intercombination transition of bosonic ytterbium

“…It is mostly caused by a variety of new applications in the physics of ultra cold atoms: from laser cooling and trapping [1,2,3] to optical frequency standards [4,5,6,7].…”

<title>Laser sources for precision spectroscopy on atomic strontium</title>

“…The transfer efficiency of the MOT to the crossed trap was found to be 10% with a maximum number of 2 × 10 5 88 Sr atoms at 2 K. At this wavelength, setting the optical-field polarization orthogonal to the magnetic field, the differential Stark shift between the 1 S 0 and 3 P 1 levels is small with respect to the transition linewidth, allowing precision spectroscopy and laser cooling even on optically confined atoms [15]. At this point, the density is high enough that collision physics (two body, three body and light assisted collisions) become the dominant mechanism controlling temperature, density, trapping lifetimes, etc.…”