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2006, Journal of the Optical Society of America B
Coherent-population-trapping resonances within the degenerate two-level system of the F=2→F'=1 transition of the 87 Rb D1 line were investigated in an uncoated Rb vapor cell by means of level-crossing-type experiments. Tuning over the two-photon resonance is achieved sweeping a magnetic field around zero value. The influence of transverse magnetic fields on the amplitude and the width of the resonances, recorded in fluorescence and absorption, were investigated in the cases of excitation with linear, circular, and elliptical laser light polarization. A theoretical analysis was performed for the case of linearly polarized excitation, the results of which are in good agreement with the experiment.
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2007, Physical Review A
2008, Physical Review A
2008, Physical Review A
2009, Physical Review A
Experimental investigation of the width, amplitude and shape of the Coherent Population Trapping (CPT) resonances for magnetic field measurements by means of a Hanle effect configuration (the single frequency CPT resonances) is presented. Different resonance width narrowing effects for increasing the sensitivity of the magnetometers are discussed. Numerical simulations based on density matrix formalism, which take into account the influence of the high rank polarization moments and the velocity distribution of the atoms have been performed for analysis of the shapes of the resonances.
2007, Optics Letters
2009, Physical Review A
2008, 15th International School on Quantum Electronics: Laser Physics and Applications
2008, Optics Express
2009, Optics Letters
2008, Journal of The Optical Society of America B-optical Physics
2003, Applied Physics B-lasers and Optics
We investigate the coherent population trapping effect occurring between the Zeeman sublevels of a given hyperfine state of Cs when excited by a single-mode diode laser, which is frequency modulated in the kHz–MHz range. In the presence of a dc magnetic field, simultaneous excitation of pairs of ground-state magnetic sublevels to common excited magnetic sublevels is performed. As a result, coherent population trapping resonance is detected at only a given modulation frequency, whose value gives a measure of the magnetic field. The parameters of the resonances are measured in order to determine the ultimate accuracy of the magnetic field measurement.
1997, The Journal of Chemical Physics
2005, Journal of the Optical Society of America B
2005, Physical Review A
2003, Optics Letters
2011, Journal of Physics B: Atomic, Molecular and Optical Physics
2003
2005, Physical Review A
2010, 16th International School on Quantum Electronics: Laser Physics and Applications
2009, Physical Review A
2005
2008
We present the first experimental observation of Coherent Population Trapping (CPT) in Potassium, obtained with kHz-frequency modulation of the laser light amplitude. It is performed by acousto-optical amplitude modulation of the radiation from an external cavity diode laser, matching the D1 line of K. The CPT resonances are detected both through K absorption and fluorescence. The resonances are studied in three kinds of K cells: i) pure-evacuated, ii) polydimethylsiloxane (PDMS)-coated-evacuated and iii) Ne-gas buffered. In all cases CPT-resonance narrowing with cell temperature is observed. In the pure-evacuated cell we registered the lowest contrast and the highest width of the resonance, while in buffered/coated cells a strong enhancement of the CPT resonance contrast up to 15% is observed. This behavior is the opposite to the one exhibited by Cs and Rb. The observed contrast enhancement in K is accompanied by more than two orders of magnitude reduction of the resonance width. The results here presented prove the advantage of using Potassium in CPT-based applications.
2010, 16th International School on Quantum Electronics: Laser Physics and Applications
2010, The Journal of Chemical Physics
2008, Journal of the Optical Society of America B
2008, Physical Review A
2009, Physical Review A
We present, experimentally and theoretically, nonlinear magneto-optical rotation (NMOR) using two spatially separated laser beams, the pump laser beam for creation and the probe laser beam for detection of the coherence between ground Zeeman sublevels. Both pump and probe lasers are tuned to Fg=2-->Fe=1 transition in R87b . With the specially designed spatial configuration of the pump and the probe
2006, Journal of The Optical Society of America B-optical Physics
2011, Optics Communications
We observe linewidths below the natural linewidth for a probe laser on a degenerate two-level F → F′ transition, when the same transition is driven by a strong control laser. We take advantage of the fact that each level of the transition is made of multiple magnetic sublevels, and use the phenomenon of electromagnetically induced transparency (EIT) or absorption (EIA) in multilevel systems. Optical pumping by the control laser redistributes the population so that only a few sublevels contribute to the probe absorption, an explanation which is verified by a density-matrix analysis of the relevant sublevels. We observe more than a factor of 3 reduction in linewidth in the D2 line of Rb in room-temperature vapor. Such subnatural features vastly increase the scope of applications of EIT, such as high-resolution spectroscopy and tighter locking of lasers to atomic transitions, since it is not always possible to find a suitable third level.
2010, International Conference on Laser Physics 2010
2009
2009
2011, Journal of Applied Physics
2001, Physical Review B
Measuring the amplitude and absolute i.e., temporal and initial phase of a monochromatic microwave field at a specific point of space and time has many potential applications, including precise qubit rotations and wavelength quantum teleportation. Here we show how such a measurement can indeed be made using resonant atomic probes via detection of incoherent fluorescence induced by a laser beam. This measurement is possible due to self-interference effects between the positive-and negative-frequency components of the field. In effect, the small cluster of atoms here act as a highly localized pickup coil, and the fluorescence channel acts as a transmission line. Measurement of the amplitude and the absolute i.e., temporal and initial phase of a monochromatic wave is challenging because in the most general condition the spatial distribution of the field around a point is arbitrary. Therefore, one must know the impedance of the system between the point of interest and the detector, and ensure that there is no interference with the ambient field. It is recently shown in the literature that the absolute phase measurement can be used for accurate qubit rotations 1–3 and quantum wavelength teleportation 4–6. Before we describe the physics behind this process, it is instructive to define precisely what we mean by the term " absolute phase. " Consider, for example, a microwave field such that the magnetic field at a position R is given by Bt = B 0 cost + x ˆ, where is the frequency of the field and is determined simply by our choice of the origin of time. The absolute phase is the sum of the temporal and initial phases—i.e., t +. In order to illustrate how this phase can be observed directly, consider a situation where a cluster of noninteracting atoms is at rest at the same location. For simplicity, we assume each atom to be an ideal two-level system where a ground state 0 is coupled to an excited state 1 by this field Bt, with the atom initially in state 0. The Hamiltonian for this interaction is H ˆ = 0 − z /2 + gt x , 1 where gt =−g 0 cost + , g 0 is the Rabi frequency, i are the Pauli matrices, and the driving frequency = corresponds to resonant excitation. We consider g 0 to be of the form g 0 t = g 0M 1 − exp−t / sw with a switching time sw relatively slow compared to other time scales in the system—i.e., sw −1 and g 0M −1. As we have shown before 2,3, without the rotating-wave approximation RWA and to the lowest order in g 0 /4, the amplitudes of 0 and 1 at any time t are as follows: C 0 t = cosg 0 tt/2 − 2 sing 0 tt/2, 2 C 1 t = ie −it+ sing 0 tt/2 + 2B * cosg 0 tt/2, 3 where i /2exp−i2t +2 and g 0 t 1/t 0 t g 0 tdt = g 0 1−t / sw −1 1 − exp−t / sw. If we produce this excitation using a / 2 pulse i.e., g 0 = /2 and measure the population of state 1 after the excitation terminates at t = , we get a signal C 1 " g 0 ,… 2 = 1/2 + sin2 +. 4 This signal contains information of both the amplitude and phase of the field Bt. The second term of Eq. 3 is related to the Bloch-Siegert shift 7,8, and we have called it the Bloch-Siegert oscillation BSO 2,3. It is attributable to an interference between the so-called corotating and counter-rotating parts of the oscillating field, with the atom acting as the nonlinear mixer. For = 0, we have the conventional Rabi flopping that is obtained with the RWA. For a stronger coupling field, where the RWA is not valid, the second term of Eq. 3 becomes important 2,3, and the population will depend now both on the Rabi frequency and the phase of the driving field. In recent years, this effect has also been observed indirectly using ultrashort optical pulses 9–11 under the name of carrier-wave Rabi flopping. However, to the best of our knowledge, the experiment we report here represents the first direct, real-time observation of this effect. From the oscillation observed, one can infer the value of 2t + , which represents the absolute phase of the second harmonic. This is equivalent to determine the absolute phase of the fundamental field, t + , modulo. In principle, a simple modification of the experiment can be used to eliminate the modulus uncertainty. Specifically, if one applies a dc magnetic field parallel to the rf field, it leads to a new oscillation in the population of either level at the fundamental frequency, with exactly the same phase as that of the driving field. In the experiment described here, we have restricted ourselves to the case of determining the absolute phase of the second harmonic only.
1996, The Journal of Chemical Physics
2008, Proceedings of SPIE - The International Society for Optical Engineering
2000, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
2008, Physical Review B