M.D. Hoogerland

A bright metastable atom source at 80 K

We describe a high flux source of cold (80 K) metastable helium atoms. The source employs a direct current nozzle discharge which produces in excess of 1015 atoms/steradian/s. Liquid nitrogen cooling of the discharge source yields atomic velocities below 900 ms−1. Such a source has practical applications for experiments concerned with laser cooling and trapping of metastable helium atoms.

Guiding of Metastable Helium Atoms through Hollow Optical Fibres

Atoms can be transported through hollow optical fibres using laser light blue-detuned from the atomic resonance, which propagates through the fibre to create a repulsive evanescent light field at the inner fibre wall. We report here the first transmission of metastable helium (2 3S1) atoms through such hollow optical fibres. Using fused silica capillaries with several different geometries, laser radiation that is blue-detuned from the 2 3S12 3P2 transition was focused into the body of the capillary via total internal reflection from a 45° bevel polished at one end. Laser fields were used with both co- and counter-propagating configurations to the atomic beam.

A practical direct current discharge helium absorption cell for laser frequency locking at 1083 nm

We report the construction of a low pressure (∼0.5 Torr) helium direct current discharge cell to lock a 1083 nm InGaAs diode laser to the 2u20093S–2u20093P transition in helium using saturated absorption spectroscopy. The direct current discharge cell has the advantage of being radio frequency noise free.

Improved spectral properties of diode lasers

We report on several complementary methods for improving the stability of a free running diode laser. We were primarily concerned with: (a) the construction of a stable power supply to reduce the main frequency and rf noise, and (b) long term drift of the laser frequency, for which we have developed a lock-in amplifier to be combined with a simple proportional-integrating circuit. While we have kept everything simple and inexpensive to construct, the stability is comparable with that of far more expensive, commercially available systems. Development and testing of our stabilization scheme was done on the distributed Bragg reflector diode lasers for use in a range of atomic collision and atom optics experiments, but it is applicable to all diode lasers, and can be used in a large range of atomic physics experiments.

Transverse laser cooling of a velocity-selected sodium atomic beam

The transverse velocity distribution of a sodium atomic beam, laser cooled in one dimension, has been measured with sub-recoil resolution. A velocity-selective detection system was employed to separate the longitudinal and transverse velocity components to provide a direct measure of the transverse velocity distribution. The effects of varying the cooling laser intensity and detuning on the derived transverse temperature are presented, and show a remarkable insensitivity to the laser intensity. Atomic velocities within a factor of two of the recoil velocity are

Mirror design for two-dimensional magneto-optic lenses and compressors

A novel mirror arrangement that enables large interaction lengths between atomic beams and laser fields by use of a small amount of laser power is presented. Its application to focusing and compression of neutral atomic beams is discussed.

Guiding of metastable helium atoms through hollow optical fibres

Summary form only given. Atom guiding through hollow optical fibres has been achieved previously using dipole light forces. Both blue and red detuned laser frequencies have been employed to create repulsive and attractive forces for light introduced into the fibre and the hole respectively. In the experiments described here, we report the first guiding of excited state helium atoms through hollow optical fibres. We employ helium atoms in the metastable 2/sup 3/S/sub 1/ state.

Electron scattering from laser-excited He atoms

Superelastic electron scattering has been observed, for the first time, from helium atoms in the state. The excited state has been prepared by optical pumping of a beam of metastable state atoms using a diode laser at , with the radiation directed in the scattering plane. The superelastic electron scattering intensity has been measured, at an incident energy of 9.2 eV and a scattering angle of , as a function of the linear polarization of the laser radiation. Comparison is made with a recent close-coupling calculation.

Hollow fibre guides for metastable helium atoms

Abstract The realisation of an atomic waveguide will be an important component for the development of future atom optic devices such as large angle atom interferometers. Hollow optical fibres that employ repulsive (blue detuned) evanescent light fields to guide the atoms are one approach to this technology. We report here on multimode guiding of metastable helium ( 2 3 S 1 ) atoms through hollow optical fibres that support multimode light fields. In order to produce efficient single-mode atom guiding, hollow fibres supporting single light mode propagation will be required to generate uniform evanescent light fields inside fibre wall. We have recently developed such a fibre and report on the suitability of its light transmission characteristics for atom waveguiding.

Single light mode hollow optical fibres for guiding metastable helium atoms

In previous experiments we have guided excited state helium atoms through hollow optical fibres. We employ helium atoms in the metastable 2/sup 3/S/sub 1/ state, and utilise the 1083 nm transition to the 2/sup 3/P/sub 2/ state to manipulate the atomic trajectories. For these atom guiding experiments, metastable helium has the inherent advantages of near unity detection efficiency and low background counts, since metastable helium de-excites on collision with the fibre wall. We have manufactured hollow fibres with a range of dimensions, some of which support single optical mode propagation. The fibres consist of a narrow (few /spl mu/m) light guiding region around the hole, surrounded by a 20-30 /spl mu/m thick region of lower refractive index. Propagation of the lowest order mode has been observed, thereby indicating that a uniform evanescent field can be created on the inside fibre wall. In addition, excitation of the two orthogonal modes has been observed under slightly different input coupling conditions. The resulting output from the fibre yields a hollow optical beam which has the potential to funnel atoms into the fibre. The results of atom guiding experiments using these fibres are presented.