A Pumped Atom Laser

Jiong Huang, Wenfeng Fan, Zhuo Wang +5 more

The misalignment error of the pumping laser in the atomic comagnetometer (ACM) dramatically diminishes the efficiency of the optical pumping process (characterized by the polarization of the hybrid atomic spin ensembles containing electron spins and nuclear spins) and deteriorates the performance of the ACM (characterized by the Allan standard deviation). In this work, a steady-state response model considering the misalignment error of the pumping laser is established and an in-situ evaluation method for this error is proposed. Based on the evaluation method, the influence of this misalignment error on the pumping efficiency and the performance of the ACM is quantitatively analyzed. Furthermore, a pumping laser alignment method based on the second harmonic of a single-beam magnetometer is then proposed, whose effectiveness is verified by experiments. The experimental results show that compared to the original ACM with the severely misaligned pumping laser, the polarization of the hybrid atomic spin ensembles of the ACM with the pumping laser aligned by the proposed method is increased by about 19%, and the corresponding Allan variance at 100s is reduced by about 40%.

Nicholas P. Robins, C. Figl, Matthew Jeppesen +2 more

Charles Samuels

Simon A. Haine, J. J. Hope, Nicholas P. Robins +1 more

A multimode model of a continuously pumped atom laser is shown to be unstable below a critical value of the scattering length. Above the critical scattering length, the atom laser reaches a steady state, the stability of which increases with pumping. Below this limit the laser does not reach a steady state. This instability results from the competition between gain and loss for the excited states of the lasing mode. It will determine a fundamental limit for the linewidth of an atom laser beam.

F. Tremblay, A. Michaud, Jean Beaubien +1 more

Rubidium maser and passive frequency standards performances rely on the efficiency of the optical pumping scheme. When using a semiconductor laser as the pumping source in such experiments, one found that the sharpness of the laser spectrum allows only the excitation of a small class of atomic velocities. The use of a frequency-modulated laser has shown great promise by largely increasing the overall pumping efficiency.1 Broadening of the narrow laser spectrum ensures the contribution of all classes of atomic velocities present in the vapor.2 Different modulation waveforms, amplitudes and frequencies have very important effects in overall optical pumping efficiency. We theoretically evaluate the efficiency of a frequency-modulated laser pumping source by studying deterministic as well as random modulation. Important considerations are obtained regarding the optimal conditions concerning the magnitude and the bandwidth of the modulation signal. Moreover a deterministic modulation must be used to lock the laser frequency by interrogating an atomic cell and synchronously detecting the transmitted intensity. Experiments conducted on a rubidium 87 maser optically pumped with a semiconductor laser confirm the predictions. In fact the oscillation of the maser was only possible with the help of the laser frequency modulation.

Keith R. Burnett