Rubidium Vapor Research Articles

Rydberg excitation through detuned microwave transition in rubidium

We study the excitation of Rydberg states in warm rubidium vapor. Using an inverted wavelength excitation scheme, we observe the effect of microwave coupling between Rydberg states through electromagnetically induced transparency. We observe AC stark shifts of the Rydberg states from the microwave coupling, and demonstrate detuned excitation to a secondary Rydberg state. These results show flexibility in the excitation process and state selection necessary for a variety of wave-mixing processes using Rydberg states.

Distant RF field sensing with a passive Rydberg-atomic transducer

We combine a rubidium vapor cell with a corner-cube prism reflector to form a passive RF transducer, allowing the detection of microwave signals at a location distant from the active components required for atomic sensing. This compact transducer has no electrical components and is optically linked to an active base station by a pair of free-space laser beams that establish an electromagnetically induced transparency scenario. Microwave signals at the transducer location are imprinted onto an optical signal which is detected at the base station. Our sensing architecture with a remote standalone transducer unit adds important flexibility to Rydberg-atom based sensing technologies, which are currently subject to significant attention. We demonstrate a ∼30 m link with no particular effort and foresee significant future prospects of achieving a much larger separation between the transducer and the base station.

Импульсные источники ИК-излучения с разрядом в смеси паров щелочных металлов

The paper presents results of research aimed at improving the serial pulsed sources of the IR-radiation based on a discharge in the cesium-mercury-xenon vapor mixture. To create the environmentally friendly gas-discharge source and increase the peak radiation strength, it proposes to replace the mercury buffer in a serial lamp with the rubidium vapor. Based on the thermodynamic analysis, necessity of using cesium as the main component in the plasma-forming medium of IR-radiation pulsed sources was proved. It was established that introduction into the cesium discharge of less than the 25 % (wt.) rubidium provided the required cesium vapor pressure and the plasma thermal conductivity. It was shown that the mass of the alloy with cesium played an important role in the discharge transition from unsaturated to the saturated vapors. Comparison results are presented in peak intensity of the studied IR-radiation gas-discharge lamps depending on amplitude and duration of the supply voltages in the repeated pulsed mode. A technique was developed to compare energy efficiency of the discharges under study, and the spectral research was performed confirming advantages of the IR-radiation pulsed source based on the cesium-rubidium-xenon discharge by the serial gas-discharge lamps

Competing van der Waals and dipole-dipole interactions in optical nanocells at thicknesses below 100 nm

To reliably register the absorption or selective reflection of laser radiation in a nanocell filled with a vapor of Cesium or Rubidium at thicknesses below 100 nm, it becomes necessary to increase the atomic density by heating the cell. It is shown that both atom-wall van der Waals (vdW) interactions and Dipole-Dipole (DD) Lorentz-Lorenz interactions cause a similar “red” shift in the frequency of resonances of about the same order, which largely increases the total frequency shift. Previously, unaccounted-for DD interaction led to an overestimation of the value of the C3 coefficient of the vdW interaction. We show for the first time that varying the nanocell thickness between 130 nm and 30 - 50 nm leads to a decrease of the C3 computed from the vdW “red” shift, i.e. we observe experimentally the so-called “retardation” of the vdW effect recently predicted in theoretical papers. The measurements were made using our unique nanometric-thin cells.

Experimental Realization of Orbital Angular Momentum Multiplexed Four-Beam Quadrature Squeezing

We experimentally generate 9 sets of orbital angular momentum (OAM) multiplexed four-beam quadrature squeezing by utilizing four-wave mixing processes in a rubidium vapor. The degree of four-beam quadrature squeezing decreases with the increase of topological charge |l|. In addition, we investigate the four-beam quadrature squeezing with OAM superposition modes. Our results provide an efficient way to generate OAM multiplexed multi-beam quadrature squeezing and may find potential applications in multi-parameter estimation.

An improved source of spin-polarized electrons based on spin exchange in optically pumped rubidium vapor

We have improved a polarized electron source in which unpolarized electrons undergo collisions with a mixture of buffer gas molecules and optically spin-polarized Rb atoms. With a nitrogen buffer gas, the source reliably provides spin polarization between 15% and 25% with beam currents >4 μA. Vacuum pump upgrades mitigate problems caused by denatured diffusion pump oil, leading to longer run times. A new differential pumping scheme allows the use of higher buffer gas pressures up to 800 mTorr. With a new optics layout, the Rb polarization is continuously monitored by a probe laser and improved pump laser power provides more constant high polarization. We have implemented an einzel lens to better control the energy of the electrons delivered to the target chamber and to preferentially select electron populations of higher polarization. The source is designed for studies of biologically relevant chiral molecule samples, which can poison photoemission-based GaAs polarized electron sources at very low partial pressures. It operates adjacent to a target chamber that rises to pressures as high as 10−4 Torr and has been implemented in a first experiment with chiral cysteine targets.

Combinations of orbital angular momentum in two degenerate four-wave mixing processes in Rb vapor

We present experimental measurements showing the combination of the orbital angular momentum (OAM) content of incident light beams in two distinct processes of degenerate four-wave mixing induced in hot rubidium vapor. These two processes, driven by the same fields, must satisfy distinct topological charge (TC) selection rules, which impose OAM conservation. These selection rules are readily obtained from the so-called overlap integral of the incident beams and allow us to control the relations between the two nonlinear signals, in particular, to characterize the conditions to obtain the two signals with symmetric or anti-symmetric TCs. The tilted lens method was employed to measure the OAM content of the output fields. We also discuss the transition from the near- to the far-field distributions of the generated signals.

Observation of the Strong Magneto-Optical Rotation of the Polarization of Light in Rubidium Vapor for Applications in Atomic Magnetometry

Nonlinear resonances in alkali metal vapor, which are detected by the magneto-optical rotation of the linear polarization of light, are actively used in quantum magnetometry to fabricate atomic magnetometers. The magneto-optical rotation in most such sensors is due to magnetic birefringence, and rotation angles usually do not exceed tens of milliradians. In this work, an experiment where magneto-optical resonances of linear polarization rotation of a probe wave are due to strong dichroism induced in a medium by a counterpropagating pump wave has been proposed. Both waves are in resonance with the Fg = 2 → Fe = 1 optical transition in the 87Rb D1 line (λ ≈ 795 nm). Experiments have been carried out with a 2-cm-long cylindrical cell filled with a buffer gas, and the maximum rotation angle is ≈390 mrad (22°) at a width of resonance of about 300 nT. The results show that the configuration proposed for the observation of magneto-optical rotation is promising for the fabrication of compact high-sensitivity atomic magnetometers.

Observation of the Strong Magneto-Optical Rotation of the Polarization of Light in Rubidium Vapor for Applications in Atomic Magnetometry

Nonlinear resonances in alkali metal vapor, which are detected by the magneto-optical rotation of the linear polarization of light, are actively used in quantum magnetometry to fabricate atomic magnetometers. The magneto-optical rotation in most such sensors is due to magnetic birefringence, and rotation angles usually do not exceed tens of milliradians. In this work, an experiment where magneto-optical resonances of linear polarization rotation of a probe wave are due to strong dichroism induced in a medium by a counterpropagating pump wave has been proposed. Both waves are in resonance with the Fg = 2 → Fe = 1 optical transition in the 87Rb D1 line (λ ≈ 795 nm). Experiments have been carried out with a 2-cm-long cylindrical cell filled with a buffer gas, and the maximum rotation angle is ≈390 mrad (22°) at a width of resonance of about 300 nT. The results show that the configuration proposed for the observation of magneto-optical rotation is promising for the fabrication of compact high-sensitivity atomic magnetometers.

Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication

We have demonstrated a Rydberg atom-based two-band communication with the optically excited Rydberg state coupled to another pair of Rydberg states by two microwave fields, respectively. The initial Rydberg state is excited by a three-color electromagnetically-induced absorption in rubidium vapor cell via cascading transitions, with all of them located in infrared bands: a 780 nm laser servers as a probe to monitor the optical transmittancy via transition 5S1/2→5P3/2, 776 nm and 1260 nm lasers are used to couple the states 5P3/2 and 5D5/2 and states 5D5/2 and 44F7/2. Experimentally, we show that two channel communications carried on the two microwave transitions influence each other irreconcilably, so that they cannot work at their most sensitive microwave-optical conversion points simultaneously. For a remarkable communication quality for both channels, the two microwave fields both have to make concessions to reach a common microwave-optical gain. The optimized balance for the two microwave intensities locates at EMW1=6.5 mV/cm and EMW2=5.5 mV/cm in our case. This mutual exclusive influence is theoretically well-explained by an optical Bloch equation considering all optical and microwave field interactions with atoms.

Single-Photon-Compatible Telecommunications-Band Quantum Memory in a Hot Atomic Gas

Tomorrow's quantum Internet will be powered by light and will work over today's telecommunication infrastructure, so we need low-noise, high-bandwidth, telecom-band quantum optical memory to enable scaling in the presence of loss and quantum operations. The authors have built such a device, using coherent two-photon absorption in warm rubidium vapor. This quantum memory stores gigahertz-bandwidth telecom-band light pulses with mean photon number less than one, and retrieves them with a signal-to-noise ratio exceeding 10${}^{4}$. This makes possible ultrahigh-fidelity storage of single-photon qubits and is compatible with quantum-dot light sources, for hybridized quantum photonic networking.

Producing slow light in warm alkali vapor using electromagnetically induced transparency

We present undergraduate-friendly instructions on how to produce light pulses propagating through warm Rubidium vapor with speeds less than 400 m/s, i.e., nearly a million times slower than c. We elucidate the role played by electromagnetically induced transparency (EIT) in producing slow light pulses and discuss how to achieve the required experimental conditions. The optical setup is presented, and details provided for preparation of pump, probe, and reference pulses of the required size, frequency, intensity, temporal width, and polarization purity. EIT-based slow light pulses provide the most widely studied architecture for creating quantum memories. Therefore, the basic concepts presented here are useful for physics and engineering majors who wish to get involved in the development of cutting-edge quantum technologies.

Efficient diffraction control using a tunable active-Raman gain medium

We present a scheme to create an all-optical tunable and lossless waveguide using a controllable coherent Raman process in an atomic rubidium vapor in an $\mathcal{N}$-type configuration. We employ a Gaussian Raman field and a Laguerre-Gaussian control field to imprint a high-contrast tunable waveguidelike feature inside the atomic medium. We numerically demonstrate that such a waveguide is able to guide arbitrary modes of a weak probe beam to several Rayleigh lengths without diffraction and absorption. Our results on an all-optical waveguide-based scheme may have potential applications in lossless image processing, high-contrast biomedical imaging, and image metrology.

Proposal for an active whispering-gallery microclock

Optical atomic clocks with compact size, reduced weight and low power consumption have broad out-of-the-lab applications such as satellite-based geo-positioning and communication engineering. Here, we propose an active optical microclock based on the lattice-trapped atoms evanescently interacting with a whispering-gallery-mode microcavity. Unlike the conventional passive clock scheme, the active operation directly produces the optical frequency standard without the need of extra laser stabilization, substantially simplifying the clock configuration. The numerical simulation illustrates that the microclock’s frequency stability reaches at 1 s of averaging, over one order of magnitude better than the recently demonstrated chip-scale optical clock that is built upon rubidium vapor cell and also more stable than current cesium fountain clocks and hydrogen masers. Our work extends the chip-scale clocks to the active fashion, paving the way towards the on-chip quantum micro-metrology, for example, the optical frequency comparison and synchronization between multiple microclocks through frequency microcombs.

Thermometry of liquid water through slow light imaging spectroscopy.

This work presents the first, to the best of our knowledge, experimental demonstration of slow light imaging spectroscopy for thermometry of liquid water. This novel technique for measuring temperature relies on detecting the spectral shift of Brillouin peaks in water using the temporal delay through a cell containing an atomic vapor. Stand-off sensing capabilities are achieved by time-domain measurements of Brillouin scattering tuned to be near a rubidium atomic resonance and passed through a cell filled with rubidium vapor. An injection seeded optical parametric oscillator (OPO) is demonstrated to be a versatile light source for slow light imaging spectroscopy applications. The narrow OPO pulse spectrum allows for a precise profiling of slow light features of rubidium and accurate tracking of the temperature dependence of Brillouin scattering spectral shift. A comparison between the experimental data and numerical simulation over a temperature range of 20 to 99 degrees Celsius shows a good agreement for both qualitative and quantitative results.

Atom-based sensing technique of microwave electric and magnetic fields via a single rubidium vapor cell.

We present an atom-based approach for determining microwave electric and magnetic fields by using a single rubidium vapor cell in a microwave waveguide. For a 87Rb cascade three-level system employed in our experiment, a weak probe laser driving the lower transition, 5S1/2→5P3/2, is first used to measure the microwave magnetic field based on the atomic Rabi resonance. When a counter-propagating strong coupling laser is subsequently turned on to drive the Rydberg transition, 5P3/2→67D5/2, the same probe laser is then used as a Rydberg electromagnetically induced transparency (EIT) probe to measure the microwave electric field by investigating the resonant microwave dressed Autler-Townes splitting (ATS). By tuning the hyperfine transition frequency of the ground state using an experimentally feasible static magnetic field, we first achieved a measurement of the microwave electric and magnetic field strength at the same microwave frequency of 6.916 GHz. Based on the ideal relationship between the electric and magnetic field components, we obtained the equivalent microwave magnetic fields by fitting the inversion to the measured microwave electric fields, which demonstrated that the results were in agreement with the experimental measurement of the microwave magnetic fields in the same microwave power range. This study provides new experimental evidence for quantum-based microwave measurements of electric and magnetic fields by a single sensor in the same system.

Digitally encoded RF to optical data transfer using excited Rb without the use of a local oscillator

We present a passive RF to optical data transfer without a local oscillator using an atomic “Rydberg” receiver. We demonstrate the ability to detect a 5G frequency carrier wave (3.5 GHz) and decode digital data from the carrier wave without the use of a local oscillator to detect the modulation of the RF signal. The encoding and decoding of the data are achieved using an intermediate frequency (IF). The rubidium vapor detects the changes in the carrier wave's amplitude, which comes from the mixing of the IF onto the carrier. The rubidium vapor then upconverts the IF into the optical domain for detection. Using this technique for data encoding and extraction, we achieve data rates up to 238 kbps with a variety of encoding schemes.

Effect of absorption oscillation of resonant radiation observed in a compact installation for hyper-polarization of 129Xe

This work presents the discovery and study of a new, to the best of our knowledge, effect of oscillation of resonant radiation absorption in optical cells with rubidium vapor in the presence of xenon and nitrogen inside an installation for xenon polarization by spin-exchange optical pumping. This effect was observed at temperatures of 100°C–130°C, partial xenon pressure exceeding 100 kPa, total gas mix pressure of 400 kPa, and power of broad-band ( Δ λ = ∼ 2 n m ) laser radiation over 2 W. The highest registered magnitude of power oscillations of the transmitted radiation exceeded 20%, the oscillation period depending on the temperature and lying in the range of 4.8–7 s. The conducted measurements of the parameters of the transmitted radiation lead to the conclusion that the discovered effect is related to concentration oscillations of the atomic rubidium vapor, which probably arises due to cyclic dimerization of rubidium or an oscillating continuous chemical reaction of rubidium and the optical cell contents.

Investigating Rubidium Density and Temperature Distributions in a High-Throughput 129Xe-Rb Spin-Exchange Optical Pumping Polarizer.

Accurate knowledge of the rubidium (Rb) vapor density, [Rb], is necessary to correctly model the spin dynamics of 129Xe-Rb spin-exchange optical pumping (SEOP). Here we present a systematic evaluation of [Rb] within a high-throughput 129Xe-Rb hyperpolarizer during continuous-flow SEOP. Near-infrared (52S1/2→52P1/2 (D1)/52P3/2 (D2)) and violet (52S1/2→62P1/2/62P3/2) atomic absorption spectroscopy was used to measure [Rb] within 3.5 L cylindrical SEOP cells containing different spatial distributions and amounts of Rb metal. We were able to quantify deviation from the Beer-Lambert law at high optical depth for D2 and 62P3/2 absorption by comparison with measurements of the D1 and 62P1/2 absorption lines, respectively. D2 absorption deviates from the Beer-Lambert law at [Rb]D2>4×1017 m−3 whilst 52S1/2→62P3/2 absorption deviates from the Beer-Lambert law at [Rb]6P3/2>(4.16±0.01)×1019 m−3. The measured [Rb] was used to estimate a 129Xe-Rb spin exchange cross section of γ′=(1.2±0.1)×10−21 m3 s−1, consistent with spin-exchange cross sections from the literature. Significant [Rb] heterogeneity was observed in a SEOP cell containing 1 g of Rb localized at the back of the cell. While [Rb] homogeneity was improved for a greater surface area of the Rb source distribution in the cell, or by using a Rb presaturator, the measured [Rb] was consistently lower than that predicted by saturation Rb vapor density curves. Efforts to optimize [Rb] and thermal management within spin polarizer systems are necessary to maximize potential future enhancements of this technology.

Temperature-shift-suppression scheme for two-photon two-color rubidium vapor clocks

We propose a scheme for interrogating a warm rubidium vapor using two different clock lasers. Performance wise, this approach is distinctly different from the recently proposed two-color two-photon rubidium clocks as our scheme does not trade off the ac Stark suppression against an increased sensitivity to the cell temperature or pressure. Instead, our approach compensates both the ac Stark shift and the temperature and pressure-induced frequency shifts. The proposed scheme also makes use of the modulation transfer technique, which enables a two orders of magnitude increase in the signal-to-noise ratio compared to traditional clocks that rely on fluorescence measurements.