Arne Schwettmann

Atom Based Vector Microwave Electrometry Using Rubidium Rydberg Atoms in a Vapor Cell

It is clearly important to pursue atomic standards for quantities like electromagnetic fields, time, length, and gravity. We have recently shown using Rydberg states that Rb atoms in a vapor cell can serve as a practical, compact standard for microwave electric field strength. Here we demonstrate for the first time that Rb atoms excited in a vapor cell can also be used for vector microwave electrometry by using Rydberg-atom electromagnetically induced transparency. We describe the measurements necessary to obtain an arbitrary microwave electric field polarization at a resolution of 0.5°. We compare the experiments to theory and find them to be in excellent agreement.

Cold Cs Rydberg-gas interactions

We present calculations of potential curves for very high-n (89D) Cs Rydberg-atom pairs, including a background electric field. From these potentials, we show that energy transfer occurs at rates of {approx}30-70 MHz, background electric fields play an important role and dipole-dipole- and quadrupole-quadrupole-induced avoided curve crossings should lead to conversion of electronic to kinetic energy, n-changing collisions, and observable ultracold long-range Rydberg molecules.

Field-programmable gate array based locking circuit for external cavity diode laser frequency stabilization

We present a locking circuit for external cavity diode lasers implemented on a field-programmable gate array (FPGA). The main advantages over traditional non-FPGA-based locking circuits are rapid reconfigurability without any soldering and a friendly user interface. We characterize the lock quality by measuring the linewidth of a locked laser using electromagnetically induced transparency in a Rb vapor cell.

Effects of electric fields on ultracold Rydberg atom interactions

The behaviour of interacting ultracold Rydberg atoms in both constant electric fields and laser fields is important for designing experiments and constructing realistic models of them. In this paper, we briefly review our prior work and present new results on how electric fields affect interacting ultracold Rydberg atoms. Specifically, we address the topics of constant background electric fields on Rydberg atom pair excitation and laser-induced Stark shifts on pair excitation.

Multiple scattering and the density distribution of a Cs MOT

Multiple scattering is studied in a Cs magneto-optical trap (MOT). We use two Abel inversion algorithms to recover density distributions of the MOT from fluorescence images. Deviations of the density distribution from a Gaussian are attributed to multiple scattering.

Spinor dynamics in an antiferromagnetic spin-1 thermal bose gas

We present experimental observations of coherent spin-population oscillations in a cold thermal, Bose gas of spin-1 23Na atoms. The population oscillations in a multi-spatial-mode thermal gas have the same behavior as those observed in a single-spatial-mode antiferromagnetic spinor Bose-Einstein condensate. We demonstrate this by showing that the two situations are described by the same dynamical equations, with a factor of 2 change in the spin-dependent interaction coefficient, which results from the change to particles with distinguishable momentum states in the thermal gas. We compare this theory to the measured spin population evolution after times up to a few hundreds of ms, finding quantitative agreement with the amplitude and period. We also measure the damping time of the oscillations as a function of magnetic field.

Stark slowing asymmetric rotors: weak-field-seeking states and nonadiabatic transitions.

Stark deceleration is one of the few methods that can be used to slow polyatomic molecules. We present calculations of Stark shift energies, a quantitative analysis of nonadiabatic transition probabilities, and orientational distribution functions applicable to typical Stark slowing conditions for the two small asymmetric rotors nitromethane and acetaldehyde. We show that asymmetric polyatomic molecules are good candidates for Stark slowing.

Analysis of long-range Cs Rydberg potential wells

We analyse bound states at long-range (R∼5 μm) for pairs of Cs atoms in the 89D and neighbouring states. These wells are due solely to avoided crossings between the van der Waals pair interaction potentials. The depth of the wells is ∼40 MHz, and vibrational spectra consist of hundreds of bound states. We present detailed calculations of the properties of two of these wells at different electric fields (∼ mV cm− 1), since the electric field changes the well depth and shape. We estimate bound-state lifetimes μs, lineshapes, and two-photon excitation and detection rates ∼Hz from the 6P state at a temperature of T = 40 μK for these molecules.

Tunable four-pass narrow spectral bandwidth amplifier for use at ∼508 nm

We report the implementation of a tunable, narrow-spectral-bandwidth, pulsed, four-pass dye-laser amplifier with strongly reduced amplified spontaneous emission. We present temporal pulse profiles, pulse spectra, and gain measurements of the amplifier output for the case of Coumarin 307 dye as the gain medium, seeded at wavelengths of ∼508 nm and pumped at 355 nm.

Long Range Cs Rydberg Molecules

We present calculations of long range Cs Rydberg molecules. The molecules are formed by multipole interactions and can be controlled using an external electric field. Experimental progress on detecting these molecules will be reviewed.