M.G. Boshier

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.

Two-Wire Waveguide and Interferometer for Cold Atoms

A versatile miniature de Broglie waveguide is formed by two parallel current-carrying wires in the presence of a uniform bias field. We derive a variety of analytical expressions to describe the guide and present a quantum theory to show that it offers a remarkable range of possibilities for atom manipulation on the submicron scale. These include controlled and coherent splitting of the wave function as well as cooling, trapping, and guiding. In particular, we discuss a novel microscopic atom interferometer with the potential to be exceedingly sensitive.

External-cavity frequency-stabilization of visible and infrared semiconductor lasers for high resolution spectroscopy

Abstract We have shown that the external cavity stabilization can be a straightforward and powerful technique for converting diode lasers of poor spectral quality into useful tools for high precision laser spectroscopy. The method requires an anti-reflection coating on one facet of the diode laser but, contrary to popular belief, this is not difficult and does not require any specialized equipment. We describe a coating procedure which can be used with standard commercial diode lasers. We have demonstrated the external cavity method using diodes at a variety of visible and infrared wavelengths. Details are given for a visible laser centered at 670 nm.

Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems

We present a general discussion of the techniques of destabilizing dark states in laser-driven atoms with either a magnetic field or modulated laser polarization. We show that the photon-scattering rate is maximized at a particular evolution rate of the dark state. We also find that the atomic-resonance curve is significantly broadened when the evolution rate is far from this optimum value. These results are illustrated with detailed examples of destabilizing dark states in some commonly trapped ions and supported by insights derived from numerical calculations and simple theoretical models.

Measurement of the 1s-2s energy interval in muonium

The 1s-2s interval has been measured in the muonium (&mgr;(+)e(-)) atom by Doppler-free two-photon pulsed laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz, in good agreement with quantum electrodynamics. The result may be interpreted as a measurement of the muon-electron charge ratio as -1-1.1(2.1)x10(-9). We expect significantly higher accuracy at future high flux muon sources and from cw laser technology.

Self-focussing in a vapour of two-state atoms

Abstract Self-focussing in a vapour of two-state homogeneously broadened atoms is examined by numerical solution of the nonlinear wave equation describing propagation of a single frequency linearly polarized CW laser field. Close to resonance, effects due to saturation of the absorption (as well as saturation of the refractive index) are found to be important. A new phenomenon is predicted: focussing of a CW laser beam tuned to exact resonance. This is explained as being due to reshaping of the beam by the saturable absorber, followed by Fresnel diffraction.

A MEASUREMENT OF THE 1S-2S TRANSITION FREQUENCY IN MUONIUM

Doppler-free two-photon laser spectroscopy has been employed to measure the 12S12−22S12 transition in the muonium atom (μ+e−). A value of 2 455 529 002(33) (46) MHz has been obtained, which agrees with QED calculations within two standard deviations. The Lamb shift contributions are tested to the level 8×10−3. The corresponding measurements in hydrogen and deuterium using the same apparatus and laser system provide a test of the applied systematic corrections and have verified the systematic error of 46 MHz quoted. The mass of the positive muon has been derived from the isotope shift in this transition and yields a value of 105.65880(29)(43) MeVc2.

Adaptive inelastic magnetic mirror for Bose-Einstein condensates

We report the reflection and focusing of a Bose-Einstein condensate by a pulsed magnetic mirror. The mirror is adaptive, inelastic, and has extremely high optical quality. Deviations from specularity are below 1 mrad rms - almost an order of magnitude better than other atomic mirrors. The mirror has been used to realize the atom-optical analog of a beam expander, producing an ultracold collimated fountain of matter waves. The results of these experiments are in good agreement with simple theoretical models.

Precise measurement of the Stark shift of the cesium D1 line

Abstract The dc Stark shift of the cesium D1 line has been observed using two 894 nm cavity-stabilized diode lasers locked to resonance signals from an atomic beam and a saturated absorption cell. The heterodyne signal obtained from the two lasers and optical measurement of the electrode spacing allow well calibrated high precision measurements to be made. The observed scalar shift is found to be 115.219 (15) kHz (kV/cm) -2 . We believe this result to be the most precise Stark shift measurement ever reported.

THERMAL MUONIUM IN VACUO FROM SILICA AEROGELS

Muonium atoms have been observed emerging into vacuum from silica aerogel surfaces with a thermal velocity distribution corresponding to a temperature of 298(10) K after stopping positive muons from a subsurface muon beam. Yields up to 2.3(3)% could be achieved for aerogel samples of 160 mg/cm3 density. They represent an interesting alternative to the SiO2 powders previously used for muonium production in vacuum.