Aidan S. Arnold

A simple extended-cavity diode laser

Operating a laser diode in an extended cavity which provides frequency-selective feedback is a very effective method of reducing the laser’s linewidth and improving its tunability. We have developed an extremely simple laser of this type, built from inexpensive commercial components with only a few minor modifications. A 780 nm laser built to this design has an output power of 80 mW, a linewidth of 350 kHz, and it has been continuously locked to a Doppler-free rubidium transition for several days.

Optical ferris wheel for ultracold atoms

We propose a versatile optical ring lattice suitable for trapping cold and quantum degenerate atomic samples. We demonstrate the realisation of intensity patterns from pairs of Laguerre-Gauss (exp(i??) modes with different ? indices. These patterns can be rotated by introducing a frequency shift between the modes. We can generate bright ring lattices for trapping atoms in red-detuned light, and dark ring lattices suitable for trapping atoms with minimal heating in the optical vortices of blue-detuned light. The lattice sites can be joined to form a uniform ring trap, making it ideal for studying persistent currents and the Mott insulator transition in a ring geometry.

Trans-spectral orbital angular momentum transfer via four-wave mixing in Rb vapor

We report the transfer of phase structure and, in particular, of orbital angular momentum from near-infrared pump light to blue light generated in a four-wave-mixing process in 85Rb vapor. The intensity and phase profile of the two pump lasers at 780 and 776 nm, shaped by a spatial light modulator, influences the phase and intensity profile of light at 420 nm, which is generated in a subsequent coherent cascade. In particular, we observe that the phase profile associated with orbital angular momentum is transferred entirely from the pump light to the blue. Pumping with more complicated light profiles results in the excitation of spatial modes in the blue that depend strongly on phase matching, thus demonstrating the parametric nature of the mode transfer. These results have implications on the inscription and storage of phase information in atomic gases.

Enhanced frequency up-conversion in Rb vapor

We demonstrate highly efficient generation of coherent 420 nm light via up-conversion of near-infrared lasers in a hot rubidium vapor cell. By optimizing pump polarizations and frequencies we achieve a single-pass conversion efficiency of 260% per Watt, significantly higher than in previous experiments. A full exploration of the coherent light generation and fluorescence as a function of both pump frequencies reveals that coherent blue light is generated close to (85)Rb two-photon resonances, as predicted by theory, but at high vapor pressure is suppressed in spectral regions that do not support phase matching or exhibit single-photon Kerr refraction. Favorable scaling of our current 1 mW blue beam power with additional pump power is predicted.

Large magnetic storage ring for Bose-Einstein condensates

Cold atomic clouds and Bose-Einstein condensates have been stored in a 10cm diameter vertically oriented magnetic ring. An azimuthal magnetic field enables low-loss propagation of atomic clouds over a total distance of 2m, with a heating rate of less than 50nK/s. The vertical geometry was used to split an atomic cloud into two counter-rotating clouds which were recombined after one revolution. The system will be ideal for studying condensate collisions and ultimately Sagnac interferometry.

A surface-patterned chip as a strong source of ultracold atoms for quantum technologies

Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter-wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices.

NONLINEAR MODELS OF THE BUMP CEPHEID HV 905 AND THE DISTANCE MODULUS TO THE LARGE MAGELLANIC CLOUD

Nonlinear pulsation models have been used to simulate the light curve of the LMC bump Cepheid HV 905. In order to reproduce the light curve accurately, tight constraints on the input parameters M, L, and Teff are required. The results, combined with accurate existing V and I photometry, yield an LMC distance modulus of 18.51 ± 0.05, and they show that the luminosity of HV 905 is much higher than expected from the mass-luminosity relation of stellar evolution theory. If we assume that the pulsation models are accurate, this suggests that there is a larger amount of convective core overshoot during the main-sequence evolution of stars with M ~ 5 M☉ than is usually assumed.

Single-laser, one beam, tetrahedral magneto-optical trap

Shimizu et al. [1] demonstrated an alternative of the usual six beam magneto-optical trap (MOT), using four independent beams in a tetrahedral configuration. We demonstrate an novel version of the four beam MOT using a triplet of mirrors, as shown in Fig. 1, to split and steer an incoming beam into three parts such that all four beams cross in the correct configuration. The polarization of each reflected beam has a circular component along the local magnetic field that generates a position-dependent force. In addition, the perfect tetrahedral configuration offers a uniformly balanced radiation pressure area, and becomes suitable for efficient sub-Doppler cooling, benefiting also from the absence of retro-reflected beams. The beam overlap volume extends above the top of the mirrors, allowing scaling to smaller dimensions, as shifting the MOT center allows optical addressing from the side. In the usual pyramid configuration [2,3], the MOT forms below the top surface of the pyramid and the absence of optical access strongly reduces any manipulation of the cold atomic cloud. In addition, a micro-fabricated tetrahedral configuration offers an ideal tool for a high phase stability optical lattice, with the benefit of fixed lattice geometry.

Smooth inductively coupled ring trap for atoms

We propose and numerically investigate a scalable ring trap for cold atoms that surmounts problems of roughness of the potential and end effects of trap wires. A stable trapping potential is formed about an electrically isolated, conducting loop in an ac magnetic field by time averaging the superposition of the external and induced magnetic fields. We investigate the use of additional fields to eliminate Majorana spin-flip losses and to create a stable trapping geometry. The possibility of microfabrication of these ring traps offers the prospect of developing Sagnac atom interferometry in atom-chip devices.

Reproducible dynamic dark ring lattices for ultracold atoms

We demonstrate the generation of highly adaptable and reproducible dark optical ring lattices, which do not require Laguerre-Gauss beams or interferometric stability. In conjunction with a magnetic trap, these scanned 2D intensity distributions will enable low-decoherence trapping and straightforward dynamic manipulation of ultracold species in annular geometries using low-intensity regions of blue-detuned light. The technique is ideal for azimuthal ratchet, Mott insulator and persistent current experiments with quantum degenerate gases.We demonstrate the optical generation of dynamic dark optical ring lattices, which do not require Laguerre-Gauss beams, large optical coherence lengths or interferometric stability. S imple control signals lead to spatial modulation and reproducible rotation, offe ring manifold possibilities for complex dynamic ring lattices. In conjun ction with a magnetic trap, these scanned 2D intensity distributions fr om a single laser beam will enable precision trapping and manipulation of ult racold species using blue-detuned light. The technique is ideal for azimut hal ratchet, Mott insulator and persistent current experiments with quantum degenerate gases.