This thesis presents the applications of some of the coherent processes in a three-level atomic system, to control spatial and temporal properties of a signal pulse. We use two Raman absorption resonances in rubidium vapor separated by a few MHz to achieve a rapidly tunable slow-light system. We control the slow-light characteristics all-optically by tuning the frequency and power of a coupling beam. A dual absorption slow-light system is known to cause less pulse broadening than a single transmission resonance system, and thus, a tunable double absorption system is advantageous. We use a four-wave mixing process to demonstrate pulse storage in rubidium vapor for times much greater than the pulse width. We demonstrate storage of both the temporal and spatial profile of the pulse. We overcome the diffusion of spatial information during the storage in warm atomic vapor by storing the Fourier transform of the image instead of an image with a flat phase. The Raman absorption resonance is also used to control the transverse refractive index profile of the signal beam. The refractive index of the signal interacting with a coupling beam in a Raman process is dependent on the coupling beam intensity. We use a first order Laguerre-Gaussian (LG01) coupling beam to create a waveguide like transverse refractive index profile. We demonstrate propagation of a focused signal beam for lengths much greater than the Rayleigh length. Finally, we demonstrate a dual absorption atomic prism, which is capable
This thesis presents the applications of some of the coherent processes in a three-level atomic system, to control spatial and temporal properties of a signal pulse. We use two Raman absorption resonances in rubidium vapor separated by a few MHz to achieve a rapidly tunable slow-light system. We control the slow-light characteristics all-optically by tuning the frequency and power of a coupling beam. A dual absorption slow-light system is known to cause less pulse broadening than a single transmission resonance system, and thus, a tunable double absorption system is advantageous. We use a four-wave mixing process to demonstrate pulse storage in rubidium vapor for times much greater than the pulse width. We demonstrate storage of both the temporal and spatial profile of the pulse. We overcome the diffusion of spatial information during the storage in warm atomic vapor by storing the Fourier transform of the image instead of an image with a flat phase. The Raman absorption resonance is also used to control the transverse refractive index profile of the signal beam. The refractive index of the signal interacting with a coupling beam in a Raman process is dependent on the coupling beam intensity. We use a first order Laguerre-Gaussian (LG01) coupling beam to create a waveguide like transverse refractive index profile. We demonstrate propagation of a focused signal beam for lengths much greater than the Rayleigh length. Finally, we demonstrate a dual absorption atomic prism, which is capable
We present a slow-light system based on dual Raman absorption resonances in warm rubidium vapor. Each Raman absorption resonance is produced by a control beam in an off-resonant $\ensuremath{\Lambda}$ system. This system combines all optical control of the Raman absorption and the low-dispersion broadening properties of the double Lorentzian absorption slow light. The bandwidth, group delay, and central frequency of the slow-light system can all be tuned dynamically by changing the properties of the control beam. We demonstrate multiple pulse delays with low distortion and show that such a system has fast switching dynamics and thus fast reconfiguration rates.
We report a new spectroscopy method achieved by combined refraction and propagation delay of light pulses passing through a prism cell filled with an atomic vapor. The atomic vapor medium has strong refractive index gradients near the atomic resonant absorption features, and these features enable the separation in time and space of different spectral features of a light pulse propagating through the vapor cell. The gradient of the refractive index leads to a slowing of the light pulse, while simultaneously, the magnitude of the refractive index and the prismatic windows or internal prism elements of the atomic vapor cell spatially separate the frequencies due to dispersion. The combination of these two effects leads to high-resolution spectral selectivity and strong suppression of out-of-band light. Applications are achieved for Rayleigh, Raman, and Thomson spectroscopy for which the wavelength of the scattering spectra tracks the wavelength of the excitation laser source. The laser is tuned such that the spectral line of interest falls near the resonance of the atomic vapor. Applications for rotational Raman spectroscopy are of particular interest since specific Raman lines can be selected while other Raman lines as well as background Rayleigh and other scattering are strongly rejected.
In this thesis we study light-matter coherence phenomena related to the interaction of a coherent laser field and the so-called Λ-system, a three-level quantum system (e.g., an atom). We observe electromagnetically induced transparency (EIT), slow and stored light in hot rubidium vapor. For example, a 6 μs Gaussian pulse propagate at a velocity of ~1 km/s (to be compared with the normal velocity of 300 000 km/s). Dynamic changes of the control parameter allows us to slow down a pulse to a complete stop, store it for ~100 μs, and then release it. During the storage time, and also during the release process, some properties of the light pulse can be changed, e.g., frequency chirping of the pulse is obtained by means of Zeeman shifting the energy levels of the Λ-system. If, bichromatic continuous light fields are applied we observe overtone generation in the beating signal, and a narrow `dip' in overtone generation efficiency on two-photon resonance, narrower than the `coherent population trapping' transparency. The observed light-matter coherence phenomena are explained theoretically from first principles, using the Lindblad master equation, in conjunction with the Maxwell's equations. Furthermore, we analyze an optical delay-line based on EIT and show that there is in principle (besides decoherence) no fundamental limitation, but the usefulness today is scant. The combination of EIT and a photonic crystal cavity is inquired into, and we show that the quality value of a small resonator (area of 2.5λ×2.5λ with a missing central rod) can be enhanced by a factor of 500 due to the increased modal density close to two-photon resonance. Open system effects (decoherence effects) are thoroughly investigated using a coherence vector formalism, furthermore, a vector form of the Lindblad equation is derived. Specifically we find an open system channel that lead to slow light and gain.
In this thesis we study light-matter coherence phenomena related to the interaction of a coherent laser field and the so-called Λ-system, a three-level quantum system (e.g., an atom). We observe electromagnetically induced transparency (EIT), slow and stored light in hot rubidium vapor. For example, a 6 μs Gaussian pulse propagate at a velocity of ~1 km/s (to be compared with the normal velocity of 300 000 km/s). Dynamic changes of the control parameter allows us to slow down a pulse to a complete stop, store it for ~100 μs, and then release it. During the storage time, and also during the release process, some properties of the light pulse can be changed, e.g., frequency chirping of the pulse is obtained by means of Zeeman shifting the energy levels of the Λ-system. If, bichromatic continuous light fields are applied we observe overtone generation in the beating signal, and a narrow `dip' in overtone generation efficiency on two-photon resonance, narrower than the `coherent population trapping' transparency. The observed light-matter coherence phenomena are explained theoretically from first principles, using the Lindblad master equation, in conjunction with the Maxwell's equations. Furthermore, we analyze an optical delay-line based on EIT and show that there is in principle (besides decoherence) no fundamental limitation, but the usefulness today is scant. The combination of EIT and a photonic crystal cavity is inquired into, and we show that the quality value of a small resonator (area of 2.5λ×2.5λ with a missing central rod) can be enhanced by a factor of 500 due to the increased modal density close to two-photon resonance. Open system effects (decoherence effects) are thoroughly investigated using a coherence vector formalism, furthermore, a vector form of the Lindblad equation is derived. Specifically we find an open system channel that lead to slow light and gain.
We study the storage of coherences in atomic rubidium vapor with a three-level coupling scheme with two ground states and one electronically excited state driven by one optical (control) and one radio frequency field. We initially store an atomic ground state coherence in the system. When retrieving the atomic coherence with a subsequent optical pulse, a second (signal) optical beam is created whose difference frequency to the control field is found to be determined by the atomic ground state's Raman transition frequency.