Local gravity measurement with the combination of atom interferometry and Bloch oscillations

We present a local measurement of gravity combining Bloch oscillations and atom interferometry. With a falling distance of 0.8 mm, we achieve a sensitivity of $2\times {10}^{-7}\text{g}$ with an integration time of 300 s. No bias associated with the Bloch oscillations has been measured. A contrast decay with Bloch oscillations has been observed and attributed to the spatial quality of the laser beams. A simple experimental configuration has been adopted where a single retroreflected laser beam performs atom launches, stimulated Raman transitions, and Bloch oscillations. The combination of Bloch oscillations and atom interferometry can thus be accomplished with an apparatus no more complex than a standard atomic gravimeter.

Figure 1

Gravimeter scheme combining Ramsey-Bordé interferometer and Bloch oscillations.

Figure 2

Scheme of Raman or Bloch laser (PM, phase modulator; Det, fast photodiode; DFB, DFB laser diode; EDFA, erbium-doped fiber amplifier; AOM, acousto-optic modulator; PPLN, periodically poled lithium niobate crystal; c, fiber coupler).

Figure 3

Launch of atoms with Bloch laser. Top: Temporal characteristics of the moving optical lattice during the launch. Bottom: Fluorescence of the atomic cloud passing through a 0.5 mm light sheet situated 32 cm below the magneto-optical trap.

Figure 4

Proportion of atoms in the state $F=2$ versus the frequency chirp $\alpha$ applied to the Raman frequency ${\omega }_R$ ($T=6$ ms, $T^{\prime }=103$ ms, 75 Bloch oscillations). The solid line is a fit with a sine function. The value of the central fringe given by the fit is ${\alpha }_0=25146575\pm 5\text{Hz}/\text{s}$.

Figure 5

Value of central fringe ${\alpha }_0=k_{\mathrm{eff}}g$ and contrast $C$ versus number of Bloch oscillations ($T=6\text{ms}$, $T^{\prime }=13\text{ms}+1.20N\text{ms}$). Each value has been obtained with a fit over $\sim$150 measurements. The solid line on the contrast graph is an exponential fit with a decay constant of $N_0=54$.

Figure 6

Contrast $C$ versus time $T$ (75 Bloch oscillations, $T^{\prime }=115\text{ms}-2T$). The solid line is an exponential fit with a decay constant of $\tau =5.4$ ms and an initial contrast value of 0.34.