We uncover a highly nontrivial dependence of the spin-noise (SN) resonance broadening induced by the intense probe beam. The measurements were performed by probing the cell with cesium vapor at the wavelengths of the transition ${6}^2S_{1/2} \leftrightarrow {6}^2P_{3/2}$ ($\mathrm{D}_2$ line) with the unresolved hyperfine structure of the excited state. The light-induced broadening of the SN resonance was found to differ strongly at different slopes of the $\mathrm{D}_2$ line and, generally, varied nonmonotonically with light power. We discuss the effect in terms of the phenomenological Bloch equations for the spin fluctuations and demonstrate that the SN broadening behavior strongly depends on the relation between the pumping and excited-level decay rates, the spin precession, and decoherence rates. To reconcile the puzzling experimental results, we propose that the degree of optical perturbation of the spin-system is controlled by the route of the excited-state relaxation of the atom or, in other words, that the act of optical excitation of the atom does not necessarily break down completely its ground-state coherence and continuity of the spin precession. Spectral asymmetry of the effect, in this case, is provided by the position of the "closed" transition $F = 4 \leftrightarrow F' = 5$ at the short-wavelength side of the line. This hypothesis, however, remains to be proven by microscopic calculations.
We observe coherent, continuous wave, 455nm blue beam production via frequency up-conversion in cesium vapor. Two infrared lasers induce strong double-excitation in a heated cesium vapor cell, allowing the atoms to undergo a double cascade and produce a coherent, collimated, blue beam co-propagating with the two infrared pump lasers.
We report on studies of simultaneous continuous-wave mirrorless lasing on multiple optical transitions, realized by pumping hot cesium vapor with laser light resonant with the 6$S_{1/2}\rightarrow 8$P$_{3/2}$ transition. The multiplicity of decay paths for the excited atoms to their ground state is responsible for the emergence of lasing in a number of transitions, observed here in at least seven wavelengths in the infrared (IR), and at two wavelengths in the blue. We study the properties of the fields generated in the cesium vapor, such as optical power, directionality and optical linewidth.
The $6S_{1/2}-5D_{5/2}$ electric quadrupole transition is investigated in Cesium vapor at room temperature via nonlinear Doppler-free 6P-6S-5D three-level spectroscopy. Frequency-resolved studies of individual E2 hyperfine lines allow one to analyze optical pumping dynamics, polarization selection rules and line intensities. It opens the way to studies of transfer of light orbital angular momentum to atoms, and the influence of metamaterials on E2 line spectra.
We report on the storage of light via the phenomenon of Coherent Population Oscillation (CPO) in an atomic cesium vapor at room temperature. In the experiment the optical information of a probe field is stored in the CPO of two ground states of a Lambda three-level system formed by the Zeeman sublevels of the hyperfine transition F = 3 - F' = 2 of cesium D2 line. We show directly that this CPO based memory is very insensitive to stray magnetic field inhomogeneities and presents a lifetime which is mainly limited only by atomic motion. A theoretical simulation of the measured spectra was also d…
We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.
We report here the first observation of electromagnetically induced transparency (EIT) in $^{20}$Ne. The power broadening of the EIT linewidth is measured as a function of neon pressure and RF excitation power. Doppler effects on the EIT broadening are found even at low pressures and low intensities, where the linewidth should be governed only by homogeneous effects.
We have demonstrated a high temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high temperature vacuum valves and glass-to-metal seals. We have observed over 50 percent absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities…
The measurement of Cesium (Cs) 7D5/2 excited state's hyperfine splitting intervals and hyperfine-interaction constants has been experimentally investigated based on ladder-type (852 nm + 698 nm) three-level Cs system (6S1/2 - 6P3/2 - 7D5/2) with room-temperature Cs atomic vapor cell. By scanning the 698-nm coupling laser's frequency, the Doppler-free high-resolution electromagnetically-induced transparency (EIT) assisted double-resonance optical pumping (DROP) spectra have been demonstrated via transmission enhancement of the locked 852-nm probe laser. The EIT-assisted DROP spectra are employe…
The fluorescence spectra of a sub-micron atomic cesium vapor layer observable under resonant excitation on D2 line have been studied in the presence of an external magnetic field. Substantial changes in amplitudes and frequency positions of the individual (resolved) hyperfine transitions have been recorded in moderate magnetic fields (up to ~ 50 Gauss). These features are caused by mixing of the hyperfine states of the upper level resulting from comparable values of the hyperfine splitting of the 62^P_{3/2} manifold and Larmor frequencies of the magnetic sublevels. The results of simulation sh…
We propose the mechanism of active Faraday optical clock, and experimentally demonstrate active Faraday optical frequency standards based on 852 nm narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standards is determined by the cesium 6 $^{2}S_{1/2}$ $F$ = 4 to 6 $^{2}P_{3/2}$ $F'$ = 4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 996(26) Hz, which is 5.3 $\times$ 10$^{3}$ times s…
We develop an analytical theory of dark resonances that accounts for the full atomic-level structure, as well as all field-induced effects such as coherence preparation, optical pumping, ac Stark shifts, and power broadening. The analysis uses a model based on relaxation constants that assumes the total collisional depolarization of the excited state. A good qualitative agreement with experiments for Cs in Ne is obtained.
We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D$_1$ line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities the cesium D$_1$ line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 gauss and a temperature of 68.0$\,^\circ$C. Experimentally, the prediction from the model is verified.…
We study a hybrid system consisting of a narrowband atomic optical resonance and the long-range periodic order of an opaline photonic nanostructure. To this end, we have infiltrated atomic cesium vapor in a thin silica opal photonic crystal. With increasing temperature, the frequencies of the opal's reflectivity peaks shift down by >20% due to chemical reduction of the silica. Simultaneously, the photonic bands and gaps shift relative to the fixed near-infrared cesium D1 transitions. As a result the narrow atomic resonances with high finesse (f/df=8E5) dramatically change shape from a usual di…
We have detected and analysed narrow high-contrast coherent population trapping (CPT) resonances, which are induced in absorption of the weak probe light beam by the counterpropagating two-frequency pumping radiation. Our experimental investigations have been carried out on example of nonclosed three level Lambda systems formed by spectral components of the Doppler broadened D2 line of cesium atoms. We have established that CPT resonances in transmission of the probe beam (in the cesium vapor), at definite conditions, may have not only more contrast but also much lesser width in comparison wit…
We use a laser-driven single (In,Ga)As quantum dot (QD) in the dressed state regime of resonance fluorescence ($T = 4$ K) to observe the four $D_1$-transition lines of alkali atomic cesium ($Cs$) vapor at room temperature. We tune the frequency of the dressing continuous-wave laser in the vicinity of the bare QD resonance $\sim 335.116$ THz ($\sim 894.592$ nm) at constant excitation power and thereby controllably tune the center and side channel frequencies of the probe light, i.e. the Mollow triplet. Resonances between individual QD Mollow triplet lines and the atomic hyperfine-split transiti…
We report the measurement of hyperfine splitting in the $7d$ $^{2}D_{3/2}$ state of $^{133}$Cs using high resolution Doppler-free two-photon spectroscopy in a Cs vapor cell. We determine the hyperfine coupling constants $A = 7.3509(9)$ MHz and $B = -0.041(8)$ MHz, which represent an order of magnitude improvement in the precision. We also obtain bounds on the magnitude of the nuclear magnetic octupole coupling constant $C$. Additionally, we measure the ac Stark shift of the $6s$ $^{2}S_{1/2} \rightarrow 7d$ $^{2}D_{3/2}$ transition at 767.8 nm to be $-49 \pm 5$ Hz/(W/cm$^2$), in agreement with…
In the conventional spin noise spectroscopy, the probe laser light monitors fluctuations of the spin orientation of a paramagnet revealed as fluctuations of its gyrotropy, i.e., circular birefringence. For spins larger than 1/2, there exists spin arrangement of a higher order---the spin alignment---which also exhibits spontaneous fluctuations. We show theoretically and experimentally that the alignment fluctuations manifest themselves as the noise of the linear birefringence. In a magnetic field, the spin-alignment fluctuations, in contrast to those of spin orientation, show up as the noise of…
Spectroscopy has played the key role in revealing, and thereby understanding, the structure of atoms and molecules. A central drive in this field is the pursuit of higher precision and accuracy so that ever more subtle effects might be discovered. Here, we report on laser absorption spectroscopy that operates at the conventional quantum limit imposed by photon shot-noise. Furthermore, we achieve this limit without compromising the accuracy of the measurement. We demonstrate these properties by recording an absorption profile of cesium vapor at the 2 parts-per-million level. The extremely high …
We develop a model to calculate nonlinear polarization in a nondegenerate four-wave mixing in diamond configuration which includes the effects of hyperfine structure and Doppler broadening. We verify the model against the experiment with $5^{2}S_{1/2}$, $5^{2}P_{3/2}$, $5^{2}D_{3/2}$ and $5^{2}P_{1/2}$ levels of rubidium 85. Treating the multilevel atomic system as a combination of many four-level systems we are able to express the nonlinear susceptibility of a thermal ensemble in a low-intensity regime in terms of Voigt-type profiles and obtain an excellent conformity of theory and experiment…
This tutorial introduces the theoretical and experimental basics of Electromagnetically Induced Transparency (EIT) in thermal alkali vapors. We first introduce a brief phenomenological description of EIT in simple three-level systems of stationary atoms and derive analytical expressions for optical transmission and dispersion under EIT conditions. Then we focus on how the thermal motion of atoms affects various parameters of the EIT system. Specifically, we analyze the Doppler broadening of optical transitions, ballistic versus diffusive atomic motion in a limited-volume interaction region, an…
We demonstrate ladder-type electromagnetically induced transparency (EIT) using an optical nanofiber suspended in a warm rubidium vapor. The signal and control fields are both guided along the nanofiber, which enables strong nonlinear interactions with the surrounding atoms at relatively low powers. Transit-time broadening is found to be a significant EIT decoherence mechanism in this tightly-confined waveguiding geometry. Nonetheless, we observe significant EIT and controlled polarization rotation using control-field powers of only a few microWatts in this relatively robust warm-atom nanofibe…
Alkali vapors, and in particular rubidium, are being used extensively in several important fields of research such as slow and stored light non-linear optics3 and quantum computation. Additionally, the technology of alkali vapors plays a major role in realizing myriad industrial applications including for example atomic clocks magentometers8 and optical frequency stabilization. Lately, there is a growing effort towards miniaturizing traditional centimeter-size alkali vapor cells. Owing to the significant reduction in device dimensions, light matter interactions are greatly enhanced, enabling n…
We present, experimentally and theoretically, a scheme for dressed-state electromagnetically induced transparency (EIT) in a three-step cascade system where a four-level system is mapped into an effective three-level system. Theoretical analysis reveals that the scheme provides coherent state control via adiabatic following and provides a generalized protocol for light storage in uniform phase spin-waves that are insensitive to motional dephasing. The three-step driving enables a number of other features including spatial selectivity of the excitation region within the atomic medium, and kick-…
We study ultra-broadband slow light in a warm Rubidium vapor cell. By working between the D1 and D2 transitions, we find a several-nm window centered at 788.4 nm in which the group index is highly uniform and the absorption is small (<1%). We demonstrate that we can control the group delay by varying the temperature of the cell, and observe a tunable fractional delay of 18 for pulses as short as 250 fs (6.9 nm bandwidth) with a fractional broadening of only 0.65 and a power leakage of 55%. We find that a simple theoretical model is in excellent agreement with the experimental results. Using th…
