0000000000315868
AUTHOR
Alexander M. Akulshin
Studies towards a directional polychromatic sodium laser guide star
In this work we discuss a mechanism for generation of a coherent source of light from the mesosphere as a new concept of directional laser guide star. In contrast to the near-isotropic spontaneous emission, nonlinear processes in atomic vapors like amplified spontaneous emission can yield highly directional emission in the forward and backward directions. Along with directional emission, excited sodium atoms also radiate at different wavelength creating a polychromatic laser guide star (PLGS). If feasible, a directional PLGS would provide a net gain in the return flux of several orders of magnitude compared to traditional LGS schemes, making possible laser-guided tip/tilt-correction in adap…
Continuous-wave mirrorless lasing at 221 μm in sodium vapors
We demonstrate backward-directed continuous-wave (cw) emission at 2.21 {\mu}m generated on the 4P3/2-4S1/2 population-inverted transition in Na vapors two-photon excited with resonant laser light at 589 and 569 nm. Our study of power and atom-number-density threshold characteristics shows that lasing occurs at sub-10 mW total power of the applied laser light. The observed 6 mrad divergence is defined mainly by the aspect ratio of the gain region. We find that mirrorless lasing at 2.21 {\mu}m is magnetic field and polarization dependent that may be useful for remote magnetometry. The presented results could help determine the requirements for obtaining directional return from sodium atoms in…
Nonlinear magneto-optical rotation in rubidium vapor excited with blue light
We present experimental and numerical studies of nonlinear magneto-optical rotation (NMOR) in rubidium vapor excited with resonant light tuned to the $5^2\!S_{1/2}\rightarrow 6^2\!P_{1/2}$ absorption line (421~nm). Contrary to the experiments performed to date on the strong $D_1$ or $D_2$ lines, in this case, the spontaneous decay of the excited state $6^2\!P_{1/2}$ may occur via multiple intermediate states, affecting the dynamics, magnitude and other characteristics of NMOR. Comparing the experimental results with the results of modelling based on Auzinsh et al., Phys. Rev. A 80, 1 (2009), we demonstrate that despite the complexity of the structure, NMOR can be adequately described with a…
Polychromatic, continuous-wave mirrorless lasing from monochromatic pumping of cesium vapor
We report on studies of simultaneous continuous-wave mirrorless lasing on multiple optical transitions, realized by pumping hot cesium vapor with laser light resonant with the 6$S_{1/2}\rightarrow 8$P$_{3/2}$ transition. The multiplicity of decay paths for the excited atoms to their ground state is responsible for the emergence of lasing in a number of transitions, observed here in at least seven wavelengths in the infrared (IR), and at two wavelengths in the blue. We study the properties of the fields generated in the cesium vapor, such as optical power, directionality and optical linewidth.
Stand-Off Magnetometry with Directional Emission from Sodium Vapors
International audience; Stand-off magnetometry allows measuring magnetic field at a distance, and can be employed in geophysical research, hazardous environment monitoring, and security applications. Stand-off magnetometry based on resonant scattering from atoms or molecules is often limited by the scarce amounts of detected light. The situation would be dramatically improved if the light emitted by excited atoms were to propagate towards the excitation light source in a directional manner. Here, we demonstrate that this is possible by means of mirrorless lasing. In a tabletop experiment, we detect free-precession signals of ground-state sodium spins under the influence of an external magne…
Spiking dynamics of frequency up-converted field generated in continuous-wave excited rubidium vapours
We report on spiking dynamics of frequency up-converted emission at 420 nm generated on the 6P3/2-5S1/2 transition in Rb vapour two-photon excited to the 5D5/2 level with laser light at 780 and 776 nm. The spike duration is less than the natural lifetime of any excited level involved in the interaction with both continuous and pulsed pump radiation. The spikes at 420 nm are attributed to temporal properties of the directional emission at 5.23 {\mu}m generated on the population inverted 5D5/2-6P3/2 transition. A link between the spiking regime and cooperative effects is discussed. We suggest that the observed stochastic behaviour is due to the quantum-mechanical nature of the cooperative eff…