Time-Domain de Broglie Wave Interferometry

Abstract

We report the development of an atom interferometer that uses optical standing waves as phase gratings and operates in the time domain. The observed signal is entirely caused by the wave nature of the atomic center-of-mass motion. The opportunities to measure recoil frequency and gravity acceleration are demonstrated. [S0031-9007(97) PACS numbers: 03.75. Dg, 06.20.Jr, 32.80.Pj, 42.50.Md Atom optics and interferometry is a field that has undergone considerable development in recent years [1]. Atom interferometric techniques have been used to make a number of new and high precision measurements. Examples are measurements of the atomic index of refraction of a gas [2], the loss of atomic coherence in spontaneous emission [3], the Earth's gravitational acceleration g [4],h͞m [5], and precise values of atomic level spacings [6,7]. Atom interferometers (AI) fall into two classes, "microfabricated structure AI" [8-10], which use microfabricated structures as beam splitters, and "optical field AI" [4][5][6][7][11][12][13][14], which use optical fields as beam splitters. The atoms in different arms of microfabricated structure AI are in the same internal state, while in optical field AI they can be in different [4][5][6][7]11], or the same [12 -14] internal states.In this paper we report the development of an optical field atom interferometer in which pulsed standing wave optical fields act as phase gratings on an "uncollimated" cloud of cold atoms. As in Refs. [8-10,12 -14] this interferometer is a "de Broglie wave" interferometer in that the beam splitters do not alter the atomic internal state; the interference occurs between different paths of the atomic center-of-mass. In contrast to optical field AI using atomic beams [12,13], all the atoms in our interferometer interact with the light fields for the same amount of time, eliminating broadening effects due to velocity dispersion, and the time delay between the standing wave fields can easily be varied. The operation of the interferometer depends critically on a mechanism similar to that occurring in photon echo formation. As in other echolike interferometers [6,7,10,11], collimation of the transverse atomic velocity distribution to better than a photon recoil momentum is not necessary. As is discussed below, a time-domain atom interferometer of this type offers a unique combination of features that are well suited to high precision measurements and complement those of other atom interferometers. We have used this interferometer to measure the recoil frequency of a 85 Rb atom and the acceleration due to gravity ("little g").In our experiments two off-resonant standing wave pulses separated by a time T are applied to a sample of cold (150 mK) 85 Rb atoms [15]. The first laser pulse imposes a spatial phase modulation on the initial atomic state, which, due to the dispersion of de Broglie waves in free space, evolves into an amplitude modulation (representing an atomic population grating). For short times this population grating can be explained as the focusing of ...

Diffraction of a Released Bose-Einstein Condensate by a Pulsed Standing Light Wave

“…Periodic collapses of the momentum splitting of the diffracted atoms were observed. The general technique of temporal atom optics of supercold BEC atoms used in our experiment is very promising for further studies of other phenomena, such as atomic beam splitters [13] and temporal atom interferometers [14]. This method permits investigation of the limiting resolution of atom lithography in the absence of chromatic aberrations and surface diffusion of deposited atoms [8].…”

Matter-wave interference using two-level atoms and resonant optical fields

“…One could have equally well ionized all the excited state atoms immediately following the pulse. The Fourier components, ρ gg (s, t) , and total density, ρ gg (r, t) = s ρ gg (s, t) e isq·r , are periodic functions having period equal to 2π/ω q and can be used to measure recoil frequency [23,35], but, in contrast to scattering by phase gratings, there is no time for which the density is uniform when ω d t ≫ 1. When all Fourier components are taken into account, and for large pulse areas (but not so large as to violate the Raman-Nath approximation),…”

“…Atom interferometers can be constructed using two or more field interaction zones [22][23][24]. In the transient echo experiment of Cahn et al [23], the vanishing of spatial modulation at the echo times t = 2T and t = 3T (but not in the immediate vicinity of the echo times) is consistent with MWAI theory [25]. Cahn et al also found that the spatial modulation vanished in the classical scattering region, ω q T ≪ 1, as it must for any MWAI.…”

Two-dimensional grating magneto-optical trap

“…Matter wave interferometry has demonstrated orders of magnitude improvement over a wide range of precision measurements [1][2][3][4][5][6][7][8]. These successes have spurred interest in transitioning cold atom devices from the lab to more demanding environments [9][10][11][12][13][14][15][16][17].…”