Nonlinear Magnetooptical Resonance in 87Rb Vapor: The Influence of Stray Magnetic Fields and Excitation Radiation Intensity on the Basic Characteristics of the Effect in Cells with Antirelaxation Coating (original) (raw)
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Shape of the coherent-population-trapping resonances and high-rank polarization moments
Physical Review A, 2007
The shape of the coherent-population-trapping ͑CPT͒ resonances was investigated theoretically and experimentally at different laser powers. The CPT resonances were observed in fluorescence on the degenerate two-level system of the ͑F =2→ F f =1͒ transition of the 87 Rb D 1 line by means of a Hanle effect configuration in an uncoated vacuum cell. Numerical simulations based on the density matrix formalism, which take into account the high-rank polarization moment ͑HRPMs͒ influence and the velocity distribution of the atoms, were used to calculate the shape of the nonlinear magnetic resonances. The comparison of the theoretical and experimental shapes of the CPT resonances demonstrated that the HRPMs influence the shape at all laser excitation powers, and this influence can be used to explain some peculiarities at the center of the CPT resonance shape.
Journal of the Optical Society of America B, 2006
Coherent-population-trapping resonances within the degenerate two-level system of the F =2→ FЈ = 1 transition of the 87 Rb D 1 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.
JETP Letters, 2012
The effect of coherent population trapping (CPT) and the resulting process of electromagnetically induced transparency (EIT) are widely implemented in metrology, magnetometry, deceleration of light and optical information coding, the problems of quantum communications, etc. (see for a review). In par ticular, the development of next generation atomic clocks is of great applied interest. Coherent pop ulation trapping underlies modern magnetometers for precise measurements of weak magnetic fields, as well as some other applications reviewed in . The behavior of the EIT resonance of Na atoms in mag netic fields of up to hundreds of Gauss was described by Motomura and Mitsunaga [7]. The absence of works on EIT in higher fields (>500 G) is probably due to the relative complexity of producing strong homo geneous magnetic fields, since the EIT resonances are formed in cells with a length of a few centimeters filled with atomic alkali vapors. An important advantage of using a thin atomic vapor column with L = 30 μm is the possibility of implementing strong permanent magnets that can produce B fields of up to thousands of Gauss over a distance of a few centimeters. The field of such permanent magnets is strongly inhomoge neous. Its gradient can be as high as 100-200 G/mm. This excludes the use of centimeter long cells. At the same time, owing to a small diameter of the vapor col umn, the variation of B is several orders of magnitude lower than the absolute value of the field. In addition, a buffer gas (neon) with a pressure of ~100 Torr is added to the cell for the following reason. As was pre viously shown , an important condition for the formation of the EIT resonance in the Λ system with the use of cells with a micron thickness is the smallness of the frequency detuning Δ between the coupling laser and the respective atomic transition. High magnetic fields automatically result in high Δ. In this case, EIT occurs for the atoms moving in the direction of the laser radiation z at the velocity V z = 2πΔ/k, where k = 2π/λ. This leads to a decrease in the time of flight τ = L/V z (where L is the distance between the cell win dows) and, consequently, to a fast increase in the phase decoherence rate (Γ 12 = 1/2πτ) between the two lower levels of the Λ system (a wall collision with a large probability results in the transition of the atom between the lower levels ). An increase in Γ 12 leads to a fast decrease in the amplitude and an increase in the width of the EIT resonance. The presence of a buffer gas (~100 Torr) greatly reduces the mean free path of the alkali atoms (down to ~1 μm). As a result, they do not reach the walls of the 30 μm cell [8].
Influence of magnetic-field inhomogeneity on nonlinear magneto-optical resonances
Physical Review A, 2006
In this work, a sensitivity of the rate of relaxation of ground-state atomic coherences to magnetic-field inhomogeneities is studied. Such coherences give rise to many interesting phenomena in light-atom interactions, and their lifetimes are a limiting factor for achieving better sensitivity, resolution, or contrast in many applications. For atoms contained in a vapor cell, some of the coherence-relaxation mechanisms are
Influence of a.c. magnetic field on the CPT resonance obtained on two level degenerated system in Rb
2007
In this communication we present an investigation of the influence of an alternative magnetic field (a.c.MF) on the Coherent Population Trapping (CPT) resonances obtained in Hanle configuration. A.c.MF applied parallel to the sweeping magnetic field creates side-bands of the CPT resonance 1 . Their position in dependence on the a.c.MF frequency and amplitude were investigated. This phenomenon was studied for the cases of linear and circular polarized laser excitation. Coherent signal due to the hexadecapole momentum created was detected. At high amplitudes of the a.c.MF alignment to orientation conversion was recorded.
Physical Review A, 2005
The investigation of the coherent-population-trapping ͑CPT͒ resonance on the degenerate two-level system of the ͑F g =2→ F e =1͒ transition of the 87 Rb D 1 line by means of a Hanle effect configuration in an uncoated vacuum cell ͓Opt. Lett. 28, 1817 ͑2003͔͒ has shown that the measured in fluorescence resonance has a complex shape-a very narrow ͑about 1 mG͒ structure superimposed on a broader one ͑about few tens of mG͒. In this work, the dependence of the width and amplitude of the CPT resonance structures are measured at different laser power densities when the registration is in fluorescence and transmission. While the narrow resonance width does not change within the limits of the accuracy of our measurements, the wide resonance width dependence is complex and is different in fluorescence and transmission. The origins of the observed resonance width narrowing of the CPT resonance structures registered in fluorescence and transmission are discussed.
Resonant nonlinear magneto-optical effects in atoms
Reviews of Modern Physics, 2002
The authors review the history, current status, physical mechanisms, experimental methods, and applications of nonlinear magneto-optical effects in atomic vapors. They begin by describing the pioneering work of Macaluso and Corbino over a century ago on linear magneto-optical effects (in which the properties of the medium do not depend on the light power) in the vicinity of atomic resonances. These effects are then contrasted with various nonlinear magneto-optical phenomena that have been studied both theoretically and experimentally since the late 1960s. In recent years, the field of nonlinear magneto-optics has experienced a revival of interest that has led to a number of developments, including the observation of ultranarrow (1-Hz) magneto-optical resonances, applications in sensitive magnetometry, nonlinear magneto-optical tomography, and the possibility of a search for parity-and time-reversal-invariance violation in atoms. CONTENTS I. Introduction 1154 II. Linear Magneto-Optics 1155 A. Mechanisms of the linear magneto-optical effects 1155 B. Forward scattering and line crossing 1156 C. Applications in spectroscopy 1158 1. Analytical spectroscopy and trace analysis, investigation of weak transitions 1158 2. Measurement of oscillator strengths 1159 3. Investigation of interatomic collisions 1160 4. Gas lasers 1160 5. Line identification in complex spectra and the search for ''new'' energy levels 1161 6. Applications in parity violation experiments 1161 7. Investigations with synchrotron radiation sources 1161 D. Related phenomena 1162 1. Magnetic depolarization of fluorescence: Hanle effect and level crossing 1162 2. Magnetic deflection of light 1163 3. The mechanical Faraday effect III. Linear vs Nonlinear Light-Atom Interactions A. Perturbative approach B. Saturation parameters IV. Early Studies of Nonlinear Magneto-Optical Effects A. Optical pumping B. Nonlinear magneto-optical effects in gas lasers C. Nonlinear effects in forward scattering D. ''Rediscoveries'' of the nonlinear magnetooptical effects V. Physical Mechanisms of Nonlinear Magneto-Optical Effects A. Bennett-structure effects B. Coherence effects C. Alignment-to-orientation conversion VI. Symmetry Considerations in Linear and Nonlinear Magneto-Optical Effects VII. Theoretical Models A. Kanorsky-Weis approach to low-power nonlinear magneto-optical rotation B. Density-matrix calculations VIII. Nonlinear Magneto-Optical Effects in Specific Situations A. Buffer-gas-free uncoated vapor cells 1. Basic features 2. Peculiarities in the magnetic-field dependence 3. Nonlinear magneto-optical effects in optically thick vapors B. Time-domain experiments C. Atomic beams and separated light fields, Faraday-Ramsey spectroscopy *This paper is dedicated to Professor Eugene D. Commins on the occasion of his 70th birthday.
Manifestation of high-rank polarization moments in the fluorescence CPT resonance
15th International School on Quantum Electronics: Laser Physics and Applications, 2008
Coherent Population Trapping (CPT) resonance obtained with linearly polarized laser beam through magnetic field sweep (Hanle configuration) was investigated in 87 Rb D 1 line. Influence of the coherence due to high-rank polarization moment (hexadecapole moment), created in the medium, on the CPT resonance shape was calculated and experimentally detected in fluorescence. It was observed as an inverted structure at a high power of excitation. To distinguish resonances due to coherence between Zeeman sub-levels with Δm F =2 from that with Δm F =4, the Larmour frequency ω L was modulated by applying an a.c. magnetic field (a.c. MF). Resonance signal at frequency corresponding to 4ω L was observed in a fluorescence, and after lock-in on the frequency corresponding to frequency difference between sub-levels Δm F =4.
Quantum Electronics, 2009
The conditions necessary to implement a single-photon pulse source using quantum filtering based on the coherent population trapping phenomenon in N -systems of atomic levels are determined. The dependences of dark resonance characteristics on laser field intensities are experimentally measured in Rb vapor. These dependences define optimum intensity ratios and pulse durations of used laser beams, at which the system can efficiently operate as a single-photon quantum filter. (CPT) [1, 2] is a subject of basic research and applied developments in the field of precision spectroscopy [2], metrology [3], magnetometry , and light pulse storage and conversion using coherent excitations in an atomic medium . In [8], generalized dark states (GDSs) of CPT in the (atom + field) system were considered; it was shown that GDSs can arise in both classical (coherent light states) and quantized (n-photon or Fock light states) fields. Of most interest is the consideration of GDSs in atomic level systems forming the so-called N -chains during interactions with light fields . The N -chain is a sequence of L Λ systems complemented by one resonance transition. Due to this additional transition playing the role of a dark state decay channel, CPT does not occur in such a system in the classical field. Nevertheless, the theoretical consideration shows that GDSs can be formed in such systems as well.
Modelling of Nonlinear Interaction of Rb 87 Atoms with Polarized Radiation
The ultra narrow resonances, obtained by means of polarization spectroscopy of alkali atoms, originate from the destruction of the laser-induced coherence in the ground state. In the case of single-frequency, near resonance excitation and suitable geometry the well-known ground state Hanle effect is observed. Coherent population trapping in Hanle configuration is a nonlinear modification of this effect, observed in the fluorescence from the upper level. The ground state coherence is transmitted from the laser field and higher rank polarization moments are created. Using the irreducible tensor operator formalism programs for numerical modelling of this effect has been developed and presented here. The velocity distribution of the atoms, the Gaussian distribution of the laser beam, stray magnetic field, and the experimental geometry are taken into account. The scheme of conversion of the octupole (κ = 3) and hexadecapole (κ = 4) polarization moments (PM) through the laser and magnetic fields into the upper level quadropoles f 2 q is proposed. The conversion of the high-rank polarization moments (PM) into observable components is also discussed. The results of the modelling are compared with the measured ones at different experimental conditions.