Fringes of total atomic density produced in an atom interferometer consisting of two off-resonant standing wave pulses were directly imaged using an ldquooptical maskrdquo technique. Fringe periods with integer fractions of the standing-wave period were observed.
We have demonstrated direct imaging of interference fringes of total atomic density with periods $\ensuremath{\lambda}∕4$ and $\ensuremath{\lambda}∕2$ for optical wavelength $\ensuremath{\lambda}$ that have been produced in a de Broglie wave atom interferometer. The imaging was done by means of an ``optical mask'' technique, which allowed us to observe subwavelength periodic patterns with a resolution of up to $\ensuremath{\lambda}∕16$. In addition, the dependence of the fringe pattern on the recoil phase and pulse area reveals quantum dynamics in the atomic center-of-mass motion. The behavior of the fringe patterns near the interference times distinguishes the effects of phase gratings from those of amplitude gratings.
We have studied sub-optical wavelength atomic gratings generated by the interference of atomic de Broglie waves in a time-domain interferometer. Three short optical standing- wave pulses, detuned from resonance with a cloud of approximately 100 (mu) K 85Rb atoms, act as phase gratings for atomic matter waves. Shortly after the first pulse, a modulation in the atomic density containing spatial harmonics of period (lambda) /2N appears ((lambda) is the optical wavelength, and N is any integer) and then rapidly vanishes due to the atomic thermal motion. The cloud maintains phase memory of this modulation, however, and the second pulse (applied at time T after the first one) results in a temporal sequence of atomic density gratings of periods (lambda) /2N. The appearance of a grating is referred to as an echo. The third pulse (and a subsequent traveling wave pulse) is used to detect these gratings. By this technique, we have created and detected in real time a grating with period (lambda) /4 at time 1.5T after the first pulse and observed new types of `echoes' caused by interaction of the de Broglie waves with all three phase gratings. This ability to produce sub-wavelength structures makes our techniques applicable to atomic beam lithography.
We have studied suboptical wavelength atomic gratings, generated by the interference of atomic de Broglie waves in a time-domain interferometer. Three short optical standing- wave pulses, detuned from resonance with a cloud of approximately 100 (mu) K85 Rb atoms, act as phase gratings for atomic matter waves. The first two standing- wave pulses, separated by time T, produce a sequence of atomic density gratings of periods $lamda/4 at time 1.5T after the first pulse. The dependence of our signals on the time separation of the pulses is in good agreement with our theoretical predictions. As far as we know, this is the first time when the formation of a high order matter-wave diffraction grating was observed in real time. This demonstrated ability to produce sub-wavelength structures makes our techniques applicable to atomic beam lithography.
An optical mask is a standing wave of light in resonance with an open atomic transition. The mask depletes the population of the initial internal state everywhere except in a narrow vicinity of the nodes. We have experimentally explored the optical mask as a tool for creating a periodic pattern in the density of cold rubidium atoms (in a particular hyperfine ground state) and also as an instrument for imaging the density in situ. The instrumental width of the imaging technique is a small fraction of the optical wavelength and is limited due to an effect of the dipole force rather than the initial velocity spread.
We have constructed an atom interferometer by Bragg deflecting a collimated beam of metastable neon atoms from three parallel standing waves. Interference fringes have been observed using atoms Bragg scattered at up to the third order, giving a maximum of $6\ensuremath{\Elzxh}k$ transverse momentum difference between the two arms of the interferometer. In the first order case we have achieved a fringe contrast of 62% and a peak to peak signal of 1700 atoms/s. We believe this to be the highest fringe contrast that has been achieved in atom interferometers.
Summary form only given.Recent developments in atom optics have led to different approaches to lithographic techniques with neutral atoms. One of these is the use of diffraction from free-standing masks, which is sometimes called atom holography. There, narrow structures arise due to matter-wave interference in the Fresnel regime. In the presented experiment, we demonstrate that the wave nature of atoms can be used to produce periodic structures with small periodicities. We used the Talbot effect in the Fresnel diffraction regime behind a microfabricated transmission grating. The Talbot effect is the self-imaging of a grating of periodicity d illuminated with plane coherent waves.