High-intesity source for excitation of resonance fluorescence in caesium

Mervyn Harold Doobov

D. A. McGillis

Collisions of the second kind between caesium and caesium, caesium and helium, and caesium and xenon atoms, leading to P p the transfer of excitation between the 6 6 P^yg states in caesium, have been investigated by studying the sensitized fluorescence in caesium vapor at pressures in the range 2x10*^ • 7x10*5 mm Hg and in vapor-inert gas mixtures.These low caesium densities, at which trapping of resonance radiation is virtually absent, were previously Inaccesible to such measurements.The use of a high intensity light source and an improved fluorescence cell in conjunction with a very sensitive detection system, permitted accurate measurements of extremely low fluorescent intensities.The total collision cross sections for the processes ô^P^yg -> and 6 %]^yg<r-G^P^yg equal 0.64x10*^^ cm® and 3.1x10*15 ^^2 for caesium-caesium collisions, 0.41x10*®® cm® and 2.7x10*®® cm® for caesium-helium collisions, and 7 .6x10 *®! cm^ and 2.9x10*1^ cm® for caesium-xenon collisions respectively.The ratios of these cross sections agree well with the values predicted by the principle of detailed balancing except for the caesiumxenon collisions, where a shielding effect has been postulated to account for the discrepancy.ill

A. Czajkowski, M. Czajkowski

Collisional transfer of excitation energy from cadmium to caesium was investigated using methods of sensitized fluorescence. A mixture of cadmium and caesium vapors at low pressure was irradiated with Cd 3263.0 Å resonance radiation producing a population of Cd (53P1) atoms whose inelastic collisions with ground-state Cs atoms resulted in a transfer of excitation energy to a close-lying S, P, D and F states in caesium. The subsequent decay of these states manifested itself in the emission of sensitized fluorescence spectrum. Intensity measurements on the components of the spectrum by means of energy calibrated detector yielded some 50 cross-section values whose magnitudes range from 0.2 Å2 to 30.0 Å2 and which exhibit a pronounced resonances with ΔE the energy defect between Cd (53P1) and the appropriate level in caesium.

Michel Pimbert, J. Cuvellier, J. Pascale +1 more

Lucy A. Downes

This thesis investigates the interaction between Rydberg atoms and THz radiation and details development of an atom-based imaging system for THz frequency fields. Room temperature caesium atoms are excited to a Rydberg state using resonant infrared lasers and the response of these atoms to THz radiation is studied in multiple ways. We look at the absorption of the initial excitation laser and show how the observed lineshape changes in response to an applied THz field. We use this to measure the power of a THz field across a range of 350 GHz. These measurements also lead us to determine values for the quantum defects in caesium without reliance on data from any other sources. These values agree within error with those previously reported in literature. We study the optical fluorescence emitted by the laser-excited \nvapour and develop a model to predict this emission. We highlight deviations from this model and suggest possible mechanisms for this discrepancy. We show how this model can be used to determine the optimum transition for atom-based THz imaging within our experimental parameters. We demonstrate a high-speed THz imaging system using Rydberg atoms and show that it has near diffraction-limited \nspatial resolution and is able to capture images at kHz framerates. We measure the minimum THz power that the system can detect and show how it compares to other technologies. This system is then used to perform some proof-of-principle experiments to highlight its usefulness in commercial settings. Using optical elements \ndesigned and produced in-house we create and characterise THz vortex beams with both radial and azimuthal phase. We show how these beams are similar to Laguerre-Gauss modes and highlight some important differences.

Leonard I. Schiff