The use of optical forces to precisely control the motion of atoms has played a major role in expanding the field of atomic physics. However, in a majority of experiments, these optical forces are limited in strength by the inherent properties of the chosen atoms, mainly the rates of spontaneous emission, required to return the atoms to their ground state. It has been shown that the process of absorption, followed by stimulated-emission, can be used to provide a more rapid return to the atomic ground state. Through careful design of the experiment, a coherent exchange of momentum can take place, exerting a large force on the atoms. Adiabatic Rapid Passage (ARP) is a technique commonly used in the magnetic resonance community for the population inversion of a two-level spin system. This technique has been expanded to the optical regime and used to invert the electronic states of an atomic system, allowing for control over both absorption and stimulated emission. It has been previously demonstrated that this scheme can be used to generate large forces on stationary atoms. An in-depth study of this ARP force will be presented with a strong emphasis on experiments designed to measure the dependence of the ARP force on atomic velocity. The experiments use the $2^3S\rightarrow2^3P$ transition in Helium at $\lambda=1.083\unit{\um}$, and results show, that by using a properly-tailored pulse sequence, the ARP force can exerts a large force on atoms over a large velocity range, making it a potential candidate to decelerate neutral atomic (or molecular) beams Numerical simulations of multiple ARP processes on two-level atoms were run with the hopes of gaining further insight into the subsequent force. These simulations have unveiled some interesting questions about the ARP process. These questions pertain to spontaneous emission's effect on the force and the influence of the phase of the optical pulses on the atomic state. While the simulations exhibit some overall similarities with the experimental results quantitative agreement is generally poor. Explanation for this disagreement is presented along with a roadmap for future work. | 91 pagesThe use of optical forces to precisely control the motion of atoms has played a major role in expanding the field of atomic physics. However, in a majority of experiments, these optical forces are limited in strength by the inherent properties of the chosen atoms, mainly the rates of spontaneous emission, required to return the atoms to their ground state. It has been shown that the process of absorption, followed by stimulated-emission, can be used to provide a more rapid return to the atomic ground state. Through careful design of the experiment, a coherent exchange of momentum can take place, exerting a large force on the atoms. Adiabatic Rapid Passage (ARP) is a technique commonly used in the magnetic resonance community for the population inversion of a two-level spin system. This technique has been expanded to the optical regime and used to invert the electronic states of an atomic system, allowing for control over both absorption and stimulated emission. It has been previously demonstrated that this scheme can be used to generate large forces on stationary atoms. An in-depth study of this ARP force will be presented with a strong emphasis on experiments designed to measure the dependence of the ARP force on atomic velocity. The experiments use the $2^3S\rightarrow2^3P$ transition in Helium at $\lambda=1.083\unit{\um}$, and results show, that by using a properly-tailored pulse sequence, the ARP force can exerts a large force on atoms over a large velocity range, making it a potential candidate to decelerate neutral atomic (or molecular) beams Numerical simulations of multiple ARP processes on two-level atoms were run with the hopes of gaining further insight into the subsequent force. These simulations have unveiled some interesting questions about the ARP process. These questions pertain to spontaneous emission's effect on the force and the influence of the phase of the optical pulses on the atomic state. While the simulations exhibit some overall similarities with the experimental results quantitative agreement is generally poor. Explanation for this disagreement is presented along with a roadmap for future work. | 91 pages

Jan 1, 20151 citation

Optical Forces from Periodic Adiabatic Rapid Passage Sequences on Metastable Helium Atoms

Daniel T. Stack

Over the past 30 years, optical manipulation of neutral atoms has been primarily performed with a monochromatic laser beam. The simplest tool for the control of atomic motion is the radiative force exerted by a monochromatic laser on a twolevel atom. The radiative force arises from absorption followed by spontaneous emission, and its magnitude is limited by the atom's excited state lifetime. The coherent momentum exchanges between light elds and atoms can be exploited to produce long-range optical forces much greater than the radiative force through the use of absorption-stimulated emission processes. Adiabatic Rapid Passage (ARP) is a long-existing method to invert the population of a two-level nuclear spin system. Its extension to the optical domain necessitates a frequency chirped light pulse to interact with a two-level atom via the dipole interaction. I will first present a numerical study of the properties of optical forces on moving atoms derived from purely stimulated processes produced by multiple ARP sequences. This will be followed by experimental observations of long-range ARP forces much larger than the radiative force in metastable helium. Sequences of properly timed laser pulses may be used for rapid deceleration of neutral atomic (or molecular) beams. | 171 pagesOver the past 30 years, optical manipulation of neutral atoms has been primarily performed with a monochromatic laser beam. The simplest tool for the control of atomic motion is the radiative force exerted by a monochromatic laser on a twolevel atom. The radiative force arises from absorption followed by spontaneous emission, and its magnitude is limited by the atom's excited state lifetime. The coherent momentum exchanges between light elds and atoms can be exploited to produce long-range optical forces much greater than the radiative force through the use of absorption-stimulated emission processes. Adiabatic Rapid Passage (ARP) is a long-existing method to invert the population of a two-level nuclear spin system. Its extension to the optical domain necessitates a frequency chirped light pulse to interact with a two-level atom via the dipole interaction. I will first present a numerical study of the properties of optical forces on moving atoms derived from purely stimulated processes produced by multiple ARP sequences. This will be followed by experimental observations of long-range ARP forces much larger than the radiative force in metastable helium. Sequences of properly timed laser pulses may be used for rapid deceleration of neutral atomic (or molecular) beams. | 171 pages

Aug 1, 20120 citations

2^3S\rightarrow2^3P

transition in Helium at $\lambda=1.083\unit{\um}$, and results show, that by using a properly-tailored pulse sequence, the ARP force can exerts a large force on atoms over a large velocity range, making it a potential candidate to decelerate neutral atomic (or molecular) beams Numerical simulations of multiple ARP processes on two-level atoms were run with the hopes of gaining further insight into the subsequent force. These simulations have unveiled some interesting questions about the ARP process. These questions pertain to spontaneous emission's effect on the force and the influence of the phase of the optical pulses on the atomic state. While the simulations exhibit some overall similarities with the experimental results quantitative agreement is generally poor. Explanation for this disagreement is presented along with a roadmap for future work. | 91 pages