Dependence of the cesium absorption D1 linewidth on the thickness of atomic vapor column

A new nanocell has been elaborated, where the thickness of the atomic vapor column varies smoothly in the range L = 350–5100 nm. The cell allows studying the behavior of the resonance absorption at the D₁ line of cesium atoms by varying the thickness from L = λ / 2 to L = 5 λ with the step λ / 2 (λ being the resonant wavelength of the laser, 894 nm) and the laser intensity. It is shown that at low laser intensities a narrowing of the resonance absorption spectrum is observed for L = (2n + 1)λ/2 (with an integer n) up to L = (7/2)λ, whereas for L = nλ the spectrum broadens. The developed theoretical model well describes the experiment.     

Ultrafast optical spectroscopy of spectral fluctuations in a dense atomic vapor

Transient four-wave mixing experiments with 100 fs pulses in a dense potassium vapor probe the electronic energy fluctuations that lead to optical decoherence. Echo-peak shift experiments yield a biexponential two-time correlation function of energy level fluctuations. Molecular dynamics simulations show that the slow component is a many-body excitonic contribution arising from long-range resonant interactions. The decay of the correlation function occurs on comparable time scales in theory and experiment.     

The influence of a probe on the optical path of atomic absorption spectrometer with a graphite tube atomizer

We have studied the influence on the atomic absorption signal of the obscuring of the transmission beam by a probe for the two-stage atomization in a graphite tube atomizer. The following parameters were varied: the thickness of the probe (0.5–1.0 mm), its displacement from the optical axis of the spectrometer (up to 2 mm), the diameter of the transmission beam (1.3–4.0 mm), the slit width of the monochromator, and the shape of the intensity distribution over the cross section of the beam emitted either by a hollow cathode lamp, or a deuterium lamp, or an electrodeless lamp. We have shown that, using a probe with a thickness that is optimal for the two-stage atomization (1 mm), it is possible to register analytical absorption signals from 28 chemical elements out of 56 (except Hg), which can be determined in graphite atomizers, with a maximal sensitivity and with no optical interference. The remaining elements can be determined with a lower sensitivity because of the necessity to lower the temperature of the secondary atomization.     

The influence of reorientational collisions on coherent optical processes

Numerical calculations of pulse transmission in SF₆ are performed to appraise the role of reorientational collisions. No support is found for the recent postutate calling for thermally equilibrated magnetic sublevels in self-induced transparency.     

Enhanced light‐vapor interactions and all optical switching in a chip scale micro‐ring resonator coupled with atomic vapor

The coupling of atomic and photonic resonances serves as an important tool for enhancing light‐matter interactions and enables the observation of multitude of fascinating and fundamental phenomena. Here, by exploiting the platform of atomic‐cladding wave guides, the resonant coupling of rubidium vapor and an atomic cladding micro ring resonator is experimentally demonstrated. Specifically, cavity‐atom coupling in the form of Fano resonances having a distinct dependency on the relative frequency detuning between the photonic and the atomic resonances is observed. Moreover, significant enhancement of the efficiency of all optical switching in the V‐type pump‐probe scheme is demonstrated. The coupled system of micro‐ring resonator and atomic vapor is a promising building block for a variety of light vapor experiments, as it offers a very small footprint, high degree of integration and extremely strong confinement of light and vapor. As such it may be used for important applications, such as all optical switching, dispersion engineering (e.g. slow and fast light) and metrology, as well as for the observation of important effects such as strong coupling, and Purcell enhancement.

     

Electromagnetically induced transparency with a train of short pulses in Rb vapor

We observe transmission of the radiation of a diode laser in the mode-locked regime through the cell containing optically dense Rb vapor under the condition where the hyperfine splitting of Rb is a multiple of the modulation frequency.     

Orientational frequency shifts of microwave 0-0 superfine resonance in 87Rb vapor with selective optical pumping

The orientational frequency shift of the UHF radio-optical resonance in the ⁸⁷Rb vapor with a selective optical pumping by laser and lamp sources is studied experimentally and theoretically. A leading role of the tensor component of the light shift is noticed for both excitation modes, and a modulation technique of the resonance frequency orientation shift suppression is demonstrated. We show that it is necessary to ensure a constancy of the angle between the pump light direction and the external magnetic field vector when using a rubidium quantum discriminator based on moving and rotating carriers.     

In-situ dual-port polarization contrast imaging of Faraday rotation in a high optical depth ultracold 87Rb atomic ensemble

We study the effects of high optical depth and density on the performance of a light-atom quantum interface. An in-situ imaging method, a dual-port polarization contrast technique, is presented. This technique is able to compensate for image distortions due to refraction. We propose our imaging method as a tool to characterize atomic ensembles for high capacity spatial multimode quantum memories. Ultracold dense inhomogeneous rubidium samples are imaged and we find a resonant optical depth as high as 680 on the D1 line. The measurements are compared with light-atom interaction models based on Maxwell-Bloch equations. We find that an independent atom assumption is insufficient to explain our data and present corrections due to resonant dipole-dipole interactions.     

光学厚度对颗粒媒质的多重散射的影响

基于辐射传播方程及多重散射基础理论,利用Fraunhofer近似,对颗粒媒质的多重散射光强进行了计算。研究了光学厚度对多重散射的影响,揭示了多重光散射的角分布特征,光强大小随光学厚度的变化,以及单散射引起的误差等方面的规律。为实际的颗粒媒质的光学测量等提供了理论根据。     

Study of optical narrow-band N-resonance formed in the vapor of isotope 87Rb atoms in an external magnetic field

Narrow-band cascade N-resonance formed in a Λ-system of rubidium atoms was investigated. Radiation of two continuous narrow-band lasers was used, one of which had a fixed frequency, while the second one was a probe laser. N-resonance may have a sub-natural width and exhibits enhancement of absorption. The behavior of N-resonance in an external magnetic field was examined with use of ⁸⁷Rb atomic vapors.     

Nonlocal stabilization of nonlinear beams in a self-focusing atomic vapor

We show that ballistic transport of optically excited atoms in an atomic vapor provides a nonlocal nonlinearity which stabilizes the propagation of vortex beams and higher order modes in the presence of a self-focusing nonlinearity. Numerical experiments demonstrate stable propagation of higher order nonlinear states (dipole, vortices, and rotating azimuthons) over a hundred diffraction lengths, before dissipation leads to decay of these structures.     

Low-light-level optical interactions with rubidium vapor in a photonic band-gap fiber

We show that rubidium vapor can be produced within the core of a photonic band-gap fiber yielding an optical depth in excess of 2,000. Our technique for producing the vapor is based on coating the inner walls of the fiber core with organosilane and using light-induced atomic desorption to release Rb atoms into the core. As an initial demonstration of the potential of this system for supporting ultralow-level nonlinear optical interactions, we perform electromagnetically induced transparency with control-field powers in the nanowatt regime, which represents more than a 1,000-fold reduction from the power required for bulk, focused geometries.     

Study on a vapor sensor based on the optical properties of porous silicon microcavities

In this paper, we set up a sensing model of PSMs (porous silicon microcavities) by applying the Bruggeman effective medium approximation theory and the transfer matrix method. In addition, we explain in detail the adsorption characteristics of porous silicon. Finally, using an experimental setup to measure the reflectivity spectrum of PSMs when the sensor is exposed to different organic vapors, the experimental results prove that it is a feasible optical sensor for the detection of organic species. Resolution of the PSMs sensor is high, response time and resume time is short and repetition is good.      

Cesium optical atomic clock: an optical pulse that tells the time

We propose a new cesium (Cs) atomic clock whose microwave source is a 9.1926-GHz harmonically and regeneratively mode-locked erbium fiber laser rather than a quartz oscillator and a multiplexer. The repetition rate of the laser is directly locked to the Cs resonance, and the frequency stability evaluated by the Allan variance is 7.1 x 10(-12) for tau = 1 s. This new atomic clock provides not only a precise 1-s time standard after demultiplexing but also an optical pulse train with the same stability, which means that the ultrastable clock signal can be delivered throughout the world by means of optical fiber networks.     

The influence of acoustic waves on the positive column of a glow discharge with standing striations

The influence was investigated of low-frequency standing acoustic waves on the positive column of a glow discharge in air and nitrogen in a regime in which spontaneous formation of standing striations readily occurs. Experimental information is presented proving that an acoustic wave of sufficient energy propagating along the discharge axis has a great influence on physical processes creating standing striations in a molecular gas.In conclusion the author would like to thank Prof. J. Kracík for his support and his interest in this work and Mr. P. Slovák for his assistance with the experimental work.     

Zeeman effect on the hyperfine structure of the D 1 line of a submicron layer of 87Rb vapor

An extremely thin cell with a wedge gap was developed that makes it possible to form a column of Rb atom vapor with thickness in the range from 100 to 600 nm. It is experimentally shown that the use of this cell, along with commercially available diode lasers, allows one to spectrally resolve individual transitions between the Zeeman sublevels of the hyperfine structure of the ⁸⁷Rb D ₁ line (transitions F _g =1, 2→F _e =1, 2) in the resonance fluorescence spectrum in the presence of an external magnetic field (B≈200 G). This makes it possible to realize systems consisting of nondegenerate atomic levels. For comparison, it is shown that transitions between the Zeeman sublevels in the fluorescence spectrum obtained with the aid of a conventional cell (1–10 cm long) in an external magnetic field with B～200 G remain completely masked by the Doppler-broadened profile. The results obtained can be used for the creation of a simple magnetometer based on an extremely thin cell with Rb vapor for the measurement of magnetic fields with a submicron local spatial resolution.     

Rubidium vapor cell miniaturization-influence on the optical pumping process

We present a comparative study of the optical pumping process in four natural mixture Rb cells with different level of miniaturization. The influence of 2 Torr Ne gas added as buffer on the optical pumping is estimated using the fluorescence spectra on the Rb D₂-line obtained by tunable single-mode circularly-polarized diode laser. The obtained results provide basic information for optimization of alkali-cell dimensions and buffer gas pressure for further coherent spectroscopy based applications.