Calcium Atomic Beam Research Articles

The setup for laser cooling and trapping of calcium atoms

We have assembled the experimental setup for laser cooling and trapping of calcium atoms in a magneto-optical trap. As a part of this setup on air-cooled Zeeman slower for calcium atomic beam was developed. By using the atomic beam we recorded the resonance of fluorescence. The spectral width of the resonance 58.6 MHz is comparable with the natural width of cooling transition 4s21S0−4s4p1P1.

Three-level atom interferometer with bichromatic laser fields

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the visibility were derived and calculated for several types of the three-level atom interferometers with bichromatic fields. Optimum excitation conditions were evaluated. Next, several types of three-level atom interferometers were demonstrated experimentally using a thermal calcium atomic beam with two Zeeman substates of $m=1$ and $m=\ensuremath{-}1$ in the long-lived excited state coupled with bichromatic resonant fields between the ground state and the excited states. The behaviors of the interference fringes were compared among them along with the calculated results. The three-level atom interferometer excited by two bichromatic laser beams separated in space was found to produce the largest visibility among them when the excitation power of each frequency component was the same.

Deceleration of a calcium atomic beam with a frequency-doubled diode laser

A calcium atomic beam has been decelerated by a single extended-cavity diode laser, frequency doubled to 423 nm. A potassium niobate crystal is placed in an external power buildup cavity, and the second-harmonic laser beam, counterpropagating with the atomic beam, is tuned into resonance with the strong 1S0-1P1 transition of calcium. For input power of 78 mW at 846 nm, we generate 22 mW at 423 nm after correction for the reflectivity of our cavity output coupler. To keep the atoms always in resonance during the deceleration process, the Zeeman tuning technique was used.

Interference fringes of the atom interferometer comprised of four copropagating traveling laser beams

An atom interferometer comprised of four copropagating traveling laser beams has been developed using a thermal calcium atomic beam and the performance of the interference fringes was investigated experimentally. The interference fringes with a visibility of 0.2 were observed at an excitation power of 0.6 mW. The signal-to-noise ratio was about 100 at an integration time of 5 ms. The equations for the interference signal were derived from the evolution matrices of spinors and the visibility was calculated in consideration of the divergent thermal atomic beam. The experimental results were described well by the present calculation.

Calcium-atom interferometer comprised of four copropagating traveling laser beams.

Four laser beams traveling in the same direction that split and reflect a thermal calcium atomic beam compose an atomic interferometer like the Mach-Zehnder optical interferometer. The interference performance of the atomic interferometer was examined by changing the phase of the induced dipole moment in the atomic wave due to the laser beams, or the phase of atomic ``wavepacket'' in an atomic trajectory due to the ac Stark effect. An interference signal with a visibility of more than 15% was obtained. This interferometer will be useful in the detection of weak signals that require a long integration time, since it is less sensitive to the fluctuation of the laser frequency compared with the optical Ramsey atomic interferometer.

Strong-field effects in coherent saturation spectroscopy of atomic beams.

We have investigated both theoretically and experimentally saturated absorption of a long-lifetime transition in a calcium atomic beam excited either by a standing wave or by two counterpropagating traveling waves. For standing-wave excitation the usual saturation dip is turned into a peak and then evolves into a triplet as the laser intensity is increased. A theoretical framework has been developed to account for the interaction of atoms with multiple-wave excitation based on a combination of free propagators and S matrices, also applicable to atomic interferometry. The shapes of the wave packets prepared by optical beam splitters are derived. The experimental size and shape of the absorption signal are reproduced by theory only when the actual laser profile is accurately represented and if the recoil physics is introduced because of multiple momentum exchanges between atoms and light in strong laser fields.

Laser cooling and deflection of a calcium atomic beam

The thermal velocity distribution of a calcium atomic beam was compressed into a narrow velocity distribution with selectable velocities. Subsequently these slow atoms were deflected by an angle of 30° by a one-dimensional optical molasses. In the deflected beam we obtained an estimated flux of several 1010 atoms/s at mean longitudinal velocities near 35 m/s and a velocity width of approximately 13 m/s. The transverse velocities of the deflected atoms were close to the one-dimensional Doppler limit. We have observed saturated absorption signals in the deflected laser-cooled beam. The reduced transit time broadening allowed us to resolve the recoil splitting in saturated absorption.

Interferometry with Ca atoms

Separated field excitation of a calcium atomic beam using four traveling laser fields represents two distinct atom interferometers utilizing the internal degrees of freedom of the atoms. Phase shifts between the atomic partial waves have been realized by phase shifts of the laser wave fields, by the ac-Stark shift, and by rotation of the interferometer (Sagnac effect). One particular interferometer can be selected by interaction of the atomic waves with extra laser fields. We furthermore report on the preparation of a laser cooled and deflected calcium atomic beam that can be utilized to largely increase the sensitivity of the interferometer.

Interferometry with Atoms

Physics and experimental results of atom interferometry are reviewed and several realizations of atom interferometers are summarized. As a typical example of an atom interferometer utilizing the internal degrees of freedom of the atom, we discuss the separated field excitation of a calcium atomic beam using four traveling laser fields and demonstrate the Sagnac effect in a rotating interferometer. The sensitivity of this interferometer can be largely increased by use of slow atoms with narrow velocity distribution. We therefore furthermore report on the preparation of a laser cooled and deflected calcium atomic beam.

Optical Ramsey spectroscopy in a rotating frame: Sagnac effect in a matter-wave interferometer.

A calcium atomic beam excited in an optical Ramsey geometry was rotated about an axis perpendicular to the plane defined by the laser beams and the atomic beam. A frequency shift of the Ramsey fringes of several kHz has been measured which is proportional to the rotation frequency of the apparatus and to the distance between the laser beams. The results can be interpreted in three equivalent ways as the Sagnac effect in a calcium-atomic-beam interferometer: in the rotating frame of the laser beams either along straight paths or along the curved trajectories of the atoms, or in the inertial atomic frame.

High-resolution velocity selecting separated-field excitation of a calcium atomic beam

It is shown that pulsed separated-field excitation provides a useful method for time-of-flight velocity selection of atomic beams. High-resolution nonlinear optical Ramsey fringes generated by one narrow velocity group have been observed at the (3P1−1S0) intercombination line of Ca. The corresponding second-order Doppler broadening deduced from the Fourier transform of the fringe signal could be reduced by about one order of magnitude from 3.7 kHz for cw separated field excitation to 0.4 kHz.

3. Calcium atomic beam source and interference beyond two meter retardation: K. W. Meissner and Victor Kaufman, J. Opt. Soc. Amer.29, No. 10, 943–944, Oct. 1959

3. Calcium atomic beam source and interference beyond two meter retardation: K. W. Meissner and Victor Kaufman, J. Opt. Soc. Amer.29, No. 10, 943–944, Oct. 1959

Calcium Atomic Beam Source and Interference beyond Two-Meter Retardation*

Fabry-Perot interference patterns of the resonance line of calcium, λ4226 A, have now been obtained at retardations of 153 and 204 cm by employing a highly collimated calcium atomic beam source in emission. The corresponding order numbers are 3.62 and 4.82 million. The appearance of these fringes suggests that the half-width of the line is less than 3×10−3 cm−1 which is one-fourth that of the proposed primary standard of length and one-tenth that of the present primary standard of wavelength. The use of an atomic beam source for the production of the length standard is discussed.

Interference at Great Retardations Obtained with a Calcium Atomic Beam Source*

By employing a calcium atomic beam source in emission and by using a beam of high collimation very clear Fabry-Perot patterns of the resonance line of calcium, λ4226 A, were obtained with retardations of 60, 78, 94, 108, 120, and 130 cm. The corresponding order numbers are about 1.42, 1.85, 2.22, 2.56, 2.84, and 3.08 million and greatly surpass those obtainable with the best conventional cooled source available at present. The good definition of the fringes obtained with the retardation of 130 cm suggests that the limit of interference is considerably higher.