Edward W. Hagley

Four-wave mixing with matter waves

The advent of the laser as an intense source of coherent light gave rise to nonlinear optics, which now plays an important role in many areas of science and technology. One of the first applications of nonlinear optics was the multi-wave mixing, of several optical fields in a nonlinear medium (one in which the refractive index depends on the intensity of the field) to produce coherent light of a new frequency. The recent experimental realization of the matter-wave ‘laser’,—based on the extraction of coherent atoms from a Bose–Einstein condensate—opens the way for analogous experiments with intense sources of matter waves: nonlinear atom optics. Here we report coherent four-wave mixing in which three sodium matter waves of differing momenta mix to produce, by means of nonlinear atom–atom interactions, a fourth wave with new momentum. We find a clear signature of a four-wave mixing process in the dependence of the generated matter wave on the densities of the input waves. Our results may ultimately facilitate the production and investigation of quantum correlations between matter waves.

Quantum key distribution with 1.25 Gbps clock synchronization

Clock recovery techniques at 1.25 Gbps enable continuous quantum key distribution at demonstrated sifted-key rates up to 1.0 Mbps. This rate is two orders of magnitude faster than has been reported previously

Efficient multiwave mixing in the ultraslow propagation regime and the role of multiphoton quantum destructive interference

We analyze a lifetime-broadened four-state four-wave-mixing (FWM) scheme in the ultraslow propagation regime and show that the generated FWM field can acquire the same group velocity and pulse shape as those of an ultraslow pump field. We show that a new type of induced transparency resulted from multiphoton destructive interference that significantly reduced the pump field loss. Such induced transparency based on multphoton destructive interference may have important applications in other nonlinear optical processes.

Imaging the phase of an evolving bose-einstein condensate wave function

We demonstrate a spatially resolved autocorrelation measurement with a Bose-Einstein condensate and measure the evolution of the spatial profile of its quantum mechanical phase. Upon release of the condensate from the magnetic trap, its phase develops a form that we measure to be quadratic in the spatial coordinate. Our experiments also reveal the effects of the repulsive interaction between two overlapping condensate wave packets and we measure the small momentum they impart to each other.

Mach-Zehnder Bragg interferometer for a Bose-Einstein condensate

We construct a Mach-Zehnder interferometer using Bose-Einstein condensed rubidium atoms and optical Bragg diffraction. In contrast to interferometers based on normal diffraction, where only a small percentage of the atoms contribute to the signal, our Bragg diffraction interferometer uses all the condensate atoms. The condensate coherence properties and high phase-space density result in an interference pattern of nearly 100% contrast. The two arms of the interferometer may be completely separated in space, making it an ideal tool that can be used to detect vortices or other topological condensate phases.

The Atom Laser

Figure 1.Atom laser beams as produced in various laboratories.

Observation of a red-blue detuning asymmetry in matter-wave superradiance

We report the first experimental observation of strong suppression of matter-wave superradiance using blue-detuned pump light and demonstrate a pump-laser detuning asymmetry in the collective atomic recoil motion. In contrast to all previous theoretical frameworks, which predict that the process should be symmetric with respect to the sign of the detuning of the pump laser from the one-photon resonance, we find that for condensates the symmetry is broken. With high condensate densities and red-detuned pump light the distinctive multi-order, matter-wave scattering pattern is clearly visible, whereas with blue detuned pump light superradiance is strongly suppressed. However, in the limit of a dilute atomic gas symmetry is restored.

Propagation of light pulse in an ultra-cold atomic vapor: mechanism for the loss of the probe field

We examine the role of nearby hyper-fine levels in a three-level transparency driven system in which a slow group velocity of light propagation is anticipated. In addition to accounting for the significant (>80%) probe field loss, our theory can accurately model the significant (near 30%) pulse broadening found in two recent experiments. Other excitation schemes for reducing the absorption from nearby levels are discussed.

Observation of Collective Atomic Recoil Motion in a Degenerate Fermion Gas

We demonstrate collective atomic recoil motion with a dilute, ultracold, degenerate fermion gas in a single spin state. By utilizing an adiabatically decompressed magnetic trap with an aspect ratio different from that of the initial trap, a momentum-squeezed fermion cloud is achieved. With a single pump pulse of the proper polarization, we observe, for the first time, multiple wave-mixing processes that result in distinct collective atomic recoil motion modes in a degenerate fermion cloud. Contrary to the case with Bose condensates, no pump-laser detuning asymmetry is present.

Synchrotron ultraviolet radiation facility SURF III

The National Institute of Standards and Technology (NIST) has operated the Synchrotron Ultraviolet Radiation Facility (SURF) continuously since the early 1960s. The original accelerator was converted into a storage ring, called SURF II, in 1974. Then in 1998, motivated mainly by limitations in the accuracy of radiometric calibrations and the wish to extend the spectrum of the emitted synchrotron radiation to shorter wavelengths, a second major upgrade was performed. This time the whole magnet system was replaced to improve the calculability and allow for higher magnetic fields. Since the recommissioning of SURF III we have been working to improve the stability of the stored electron beam through modifications of the radio-frequency system, leading to operations with unprecedented stability and new record injection currents topping 700 mA.