Wide range linear magnetometer based on a sub-microsized K vapor cell.

39K atoms have the smallest ground state (2S1/2) hyperfine splitting of all the most naturally abundant alkali isotopes and, consequently, the smallest characteristic magnetic field value B0=A2S1/2/µB≈170G, where A2S1/2 is the ground state's magnetic dipole interaction constant. In the hyperfine Paschen-Back regime (B≫B0, where B is the magnitude of the external magnetic field applied on the atoms), only eight Zeeman transitions are visible in the absorption spectrum of the D1 line of 39K, while the probabilities of the remaining 16 Zeeman transitions tend to zero. In the case of 39K, this behavior is reached already at relatively low magnetic field B>B0. For each circular polarization (σ-,σ+), four spectrally resolved atomic transitions having sub-Doppler widths are recorded using a sub-microsized vapor cell of thickness L=120-390nm. We present a method that allows to measure the magnetic field in the range of 0.1-10kG with micrometer spatial resolution, which is relevant in particular for the determination of magnetic fields with large gradients (up to 3 G/µm). The theoretical model describes well the experimental results.

Approach to quantitative spectroscopy of atomic vapor in optical nanocells.

We present a method for recovery of narrow homogeneous spectral features out of a broad inhomogeneous overlapped profile based on second-derivative processing of the absorption spectra of alkali metal atomic vapor nanocells. The method is shown to preserve the frequency positions and amplitudes of spectral transitions, thus being applicable for quantitative spectroscopy. The proposed technique was successfully applied and tested for measurements of hyperfine splitting and atomic transition probabilities, development of an atomic frequency reference, determination of isotopic abundance, study of atom-surface interaction, and determination of magnetic-field-induced modification of atomic transition frequency and probability. The obtained experimental results are fully consistent with theoretical modeling.

Collective Lamb Shift of a Nanoscale Atomic Vapor Layer within a Sapphire Cavity.

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb shift. A complete model including the multiple reflections in the nanocell reproduces accurately the observed line shape. It allows the extraction of a density-dependent shift and width of the bulk atomic medium resonance, deconvolved from the cavity effect. We observe an additional, unexpected dependence of the shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

[A Compact Source of Terahertz Radiation Based on Interaction of Electrons in à Quantum Well with an Electromagnetic Wave of a Corrugated Waveguide].

Coherent sources of electromagnetic waves in the terahertz frequency range are very promising for various applications, including biology and medicine. In this paper we propose a scheme of a compact terahertz source, in which terahertz radiation is generated due to effective interaction of electrons in a quantum well with an electromagnetic wave of a corrugated waveguide. We have shown that the generation of electromagnetic waves with a frequency of 1012 sec(-1) and an output power of up to 25. mW is possible in the proposed scheme.

Saturated-absorption spectroscopy revisited: atomic transitions in strong magnetic fields (>20 mT) with a micrometer-thin cell.

The existence of crossover resonances makes saturated-absorption (SA) spectra very complicated when external magnetic field B is applied. It is demonstrated for the first time, to the best of our knowledge, that the use of micrometric-thin cells (MTCs, L≈40 µm) allows application of SA for quantitative studies of frequency splitting and shifts of the Rb atomic transitions in a wide range of external magnetic fields, from 0.2 up to 6 kG (20-600 mT). We compare the SA spectra obtained with the MTC with those obtained with other techniques and present applications for optical magnetometry with micrometer spatial resolution and a broadly tunable optical frequency lock.

Optical response of gas-phase atoms at less than λ/80 from a dielectric surface.

We present experimental observations of atom-light interactions within tens of nanometers (down to 11 nm) of a sapphire surface. Using photon counting we detect the fluorescence from of order one thousand Rb or Cs atoms, confined in a vapor with thickness much less than the optical excitation wavelength. The asymmetry in the spectral line shape provides a direct readout of the atom-surface potential. A numerical fit indicates a power law -C(α)/r(α) with α = 3.02 ± 0.06 confirming that the van der Waals interaction dominates over other effects. The extreme sensitivity of our photon-counting technique may allow the search for atom-surface bound states.

Cooperative Lamb shift in an atomic vapor layer of nanometer thickness.

We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using a nanothickness atomic vapor layer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift, which has a spatial frequency equal to twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for nonlinear optics.

Maximal refraction and superluminal propagation in a gaseous nanolayer.

We present an experimental measurement of the refractive index of high density Rb vapor in a gaseous atomic nanolayer. We use heterodyne interferometry to measure the relative phase shift between two copropagating laser beams as a function of the laser detuning and infer a peak index n=1.26±0.02, close to the theoretical maximum of 1.31. The large index has a concomitant large index gradient creating a region with steep anomalous dispersion where a subnanosecond optical pulse is advanced by >100 ps over a propagation distance of 390 nm, corresponding to a group index n(g)=-(1.0±0.1)×10(5), the largest negative group index measured to date.

Are the thalamic projections of nucleus Z of the medulla oblongata reorganized after partial deafferentation of the ventrolateral nucleus of the thalamus?

The possible plastic reorganization of projections from the somatosensory relay nucleus Z of the cat medulla oblongata to the partially deafferented ventrolateral nucleus of the thalamus was studied by retrograde labeling with horseradish peroxidase. Partial deafferentation of the ventrolateral nucleus of the thalamus was produced by prior (three months) electrolytic destruction of the contralateral cerebellar interpositus nucleus or the lateral vestibular nucleus of Deiters. The results demonstrated local intense labeling of a group of neurons in nucleus Z, and there was a small group of labeled neurons in cell group x of the vestibular complex projecting to the ventrolateral nucleus of the thalamus, where these projections were found to overlap with those from the cerebellar nuclei. After lesioning of the cerebellar interpositus nucleus or lateral vestibular nucleus of Deiters, ipsilateral projections in the monosynaptic circuit consisting of nucleus Z and the ventrolateral nucleus of the thalamus did not form. The absence of reorganization of projections from nucleus Z to the ventrolateral nucleus of the thalamus in terms of the formation of ipsilateral projections may be associated with its being part of the somatosensory relay nucleus, which is specialized for relaying and transmitting information strictly of the specific proprioceptive modality.

Substance use disorders and treatment utilization among MDMA users: Results from The National Epidemiologic Survey on Alcohol and Related Conditions.

The study examined the prevalence and correlates of substance use disorders and treatment utilization among lifetime MDMA users. Secondary analyses were conducted on data from the 2001-2002 NESARC, a nationally representative survey of adults in the United States. Lifetime MDMA use was assessed, and MDMA users (n = 562) were compared to a matched sample of non-MDMA users. Substance use diagnoses were made using the AUDADIS - DSM-IV, and data on treatment utilization were collected. MDMA use was significantly related to lifetime and past year substance use disorders as well as treatment utilization in bivariate analyses. Multivariate analysis, however, showed that MDMA use was not related to lifetime substance use diagnosis or to treatment utilization. MDMA use still had the strongest association with past year substance use disorders.

New manifestation of atomic parity violation in cesium: a chiral optical gain induced by linearly polarized 6S-7S excitation.

We have detected, by using stimulated emission, an atomic parity violation (APV) in the form of a chiral optical gain of a cesium vapor on the 7S-6P(3/2) transition, consecutive to linearly polarized 6S-7S excitation. We demonstrate the validity of this detection method of APV, by presenting a 9% accurate measurement of expected sign and magnitude. We stress several advantages of this new approach which fully exploits the cylindrical symmetry of the setup. Future measurements at the percent level will provide an important cross-check of an existing more precise result obtained by a different method.

Frequency-stabilized high-power ruby laser Q switched by Rb(2) vapor.

Passive Q switching of a ruby laser by the use of molecular rubidium (Rb(2)) vapor has been realized. For the first time, to our knowledge, an integrally sapphire cell containing Rb(2) vapor was used as the saturable absorber, which ensures an operation period of several years. Single-frequency-stabilized giant pulses with 700-mJ energy, 22-ns duration, and 200-MHz spectral width were obtained.

Wide-bandwidth adjustable Q switch based on rubidium dimers.

A new type of Q switching for a flash-lamp-pumped Nd:YAG laser based on the saturable absorption of rudibium dimers is demonstrated. The variation of laser parameters such as output energy, pulse length, and repetition rate by means of temperature-controlled vapor pressure is shown. For a temperature of 320°C, a train of 40-ns pulses separated by 6-µs intervals is generated. When the temperature is 360°C, a single giant pulse with energy of 100 mJ and a pulse length of 10-15 ns is observed. Comparison with a solid-state passive Q switch based on LiF is provided. The new cell construction, consisting of a sealed-off sapphire cell containing rubidium vapor, is proposed for reliable, efficient, adjustable Q switchingthat is applicable to all types of solid-state lasers. The advantages of this mechanism of Q switching, such as thermal insensitivity, frequency locking and line narrowing, and wide spectral bandwidth, covering 0.6-1.3 µm, are discussed.