Strong enhancement of group refractive index in a dense buffered atomic vapor is recorded using a technique of reflection from a low-finesse Fabry–Perot cavity filled with dense atomic vapor allowing the retrieval of a dispersion curve for the hyperfine structure of Rb D2 line buffered by a high-density Cs vapor. Oscillations of the recorded signal resulting from interference of beams reflected from the front and rear windows of the cell appearing with the laser frequency scanning across the resonance allow easy reconstruction of the dispersion curve. Contribution from concomitant interconnected processes, in particular, the determinative role of radiation channeling in enhancement of the resonator Q-factor, is analyzed.
Strong enhancement of group refractive index in a dense buffered atomic vapor is recorded using a technique of reflection from a low-finesse Fabry–Perot cavity filled with dense atomic vapor allowing the retrieval of a dispersion curve for the hyperfine structure of Rb D2 line buffered by a high-density Cs vapor. Oscillations of the recorded signal resulting from interference of beams reflected from the front and rear windows of the cell appearing with the laser frequency scanning across the resonance allow easy reconstruction of the dispersion curve. Contribution from concomitant interconnected processes, in particular, the determinative role of radiation channeling in enhancement of the resonator Q-factor, is analyzed.
In this work we investigate the transmission in an optical cell containing an atomic vapor, when a laser is tuned to the wings of the Doppler line, presenting inhomogeneous broadening. The experiment is designed to detect the transmission of a laser beam through a an atomic cesium vapor within a quartz cell. Due to the high atomic density in the 1 mm cell, the laser beam is totally absorbed at resonance. On the other hand, when the detuning by few GHz from the center of the line an oscillatory signal is observed as a function of the laser frequency. The amplitude of the transmission signal varies linearly with the laser intensity. These oscillations exhibit diferent behavior as we change some parameters of the system, and the rate of the oscillations vary with laser detuning and on the atomic density. The phase of the transmited field is also sensitive to the angle of incidence of the laser beam in the cell, which allows to vary the lineshape of the signal without changing the parameters of the laser (intensity, frequency, ...) or atomic vapor. Out of resonance with the atomic vapor, the parallel windows of commercial optical cell cavity works as a low finesse Fabry-Pérot with a free spectral range of 150 GHz. However, in resonance, the optical path of the cavity changes varies with frequency due to the dispersive response of the atomic vapor. This study experimentally characterized the transmission signal through a cavity containing resonant vapor as a function of intensity and frequency of the laser, as well as its dependence on the angle of incidence of the beam. A numerical model that allows to determine the collisional broadening of the atomic vapor adjusting the spectral curves of the transmission signal was developed. As an application, exploring the oscillations in the wings of the resonance, we can lock the laser frequency at a few GHz off the center of the atomic resonance. The lock was performed in the frequency range between 0,8 GHz and 2,4 GHz from the center of the D2 line of cesium. To characterize the locking stability we measure the optical beat signal between two similar experiments, using the same locking technique.
We studied selective reflection (SR) of laser radiation from a window of a nanocell with thickness L ~ λ 1,2 /2 filled with Rb and Cs atoms, where λ 1 = 780 nm and λ 2 = 852 nm are the wavelengths resonant with the D 2 laser lines for Rb and Cs, respectively. It is demonstrated that the negative derivative of the SR signal profile for L > λ /2 changes to the positive one for L < λ /2. It is shown that the real-time formation of the SR signal profile derivative (SRD) with the spectral width 30–40 MHz and located at the atomic transition is, in particular, a convenient frequency marker of D 2 transitions in Rb and Cs. The amplitudes of SRD signals are proportional to the atomic transition probabilities. A comparison with the known saturated absorption (SA) method demonstrated a number of advantages, such as the absence of cross-over resonances in the SRD spectrum, the simplicity of realization, a low required power, etc. An SRD frequency marker also operates in the presence of the Ne buffer gas at a pressure of 6 Torr, which allowed us to determine the Ne–Rb collisional broadening, whereas the SA method is already inapplicable at buffer gas pressures above 0.1 Torr. The realization simplicity makes the SRD method a convenient tool for atomic spectroscopy. Our theoretical model well describes the SRD signal.
In the sealed-off cesium vapor cell studied in this work, a residual rubidium fraction of approximately $\sim1%wasobserved.WeinvestigatetheopticalresponseofthesetraceRbatomsinasealed1cmlongCs−filledvaporcell.Despitethelowconcentration,laserexcitationat795nmallowstheobservationofsaturatedabsorptionandelectromagneticallyinducedtransparency(EIT)resonances.ThesurroundingCsvaporeffectivelyactsasabuffermedium,reducingtheRbatomicvelocityandincreasingtheinteractiontimewiththelaserfield,whichimprovestheEITsignal.Theexperimentsareperformedinanall−sapphirecellthatcanbeheatedupto500^{\circ}$C without window blackening, unlike conventional glass cells. From the measured spectra, Cs--Rb collisional cross sections are estimated. These results show that residual atomic species in high-temperature vapor cells can be exploited for spectroscopic and nonlinear-optical studies.
We report the preliminary results of experimental studies of a dense cesium vapor in all-sapphire sealed-off Cs cell (temperature up to 500 °C, atomic and molecular densities up to 1018 and 3.2x1016 cm-3, respectively) in selective reflection (SR) configuration. Probing the vapor by a 780 nm laser radiation scanned in 20 GHz range, we have observed a spectral structure, which appears in the vapor temperature range of 250 - 400 °C. Though the cell is filled with pure cesium, starting from 300 °C we have revealed a noticeable SR contribution of rubidium atomic D2 line transitions that fall in the laser tuning range. The spectral features observed in present work can be attributed not only to cesium dimers (Cs2) having absorption band in this spectral region, but also to RbCs molecules. Relevant spectroscopic properties of these molecules are also addressed. We believe this is the first observation of selective reflection from the interface of dielectric and molecular vapor. More experiments and theoretical treatment is required to clarify the mechanisms involved and identify the origin of each spectral component, the further work program is outlined.
View Video Presentation: https://doi.org/10.2514/6.2022-3365.vid In this work, we demonstrate a new high throughput, high resolution spectroscopic technique based on dispersion in cesium atomic vapor and use it to image the Rayleigh-Brillouin spectrum from air. This is accomplished by utilizing a prism shaped cesium vapor cell and taking advantage of the steep refractive index in the vicinity of atomic resonances of the cesium D2 hyperfine lines at 852.113 nm. A laser beam from a tunable, continuous, and narrow linewidth Ti:sapphire laser was focused in ambient air and the spectrally dispersed scattering was imaged onto a camera after passing through a 80 mm long cesium prism vapor cell. The strong dispersion enables the measurement of the characteristic thermal and acoustic broadening of the Rayleigh-Brillouin scattering. Mie scattering from particles in the air is also captured and can be separated from molecular Rayleigh-Brillouin scattering by tuning close to the cesium resonance. The trade-off between spectral resolution by dispersion and loss of signal by cesium absorption is analyzed by tuning the laser. This technique shows the feasibility to measure the thermodynamic properties of a gas by reconstruction of the Rayleigh-Brillouin spectrum and could be applicable for advanced LIDAR measurements of atmospheric properties.
In this work we investigate the transmission in an optical cell containing an atomic vapor, when a laser is tuned to the wings of the Doppler line, presenting inhomogeneous broadening. The experiment is designed to detect the transmission of a laser beam through a an atomic cesium vapor within a quartz cell. Due to the high atomic density in the 1 mm cell, the laser beam is totally absorbed at resonance. On the other hand, when the detuning by few GHz from the center of the line an oscillatory signal is observed as a function of the laser frequency. The amplitude of the transmission signal varies linearly with the laser intensity. These oscillations exhibit diferent behavior as we change some parameters of the system, and the rate of the oscillations vary with laser detuning and on the atomic density. The phase of the transmited field is also sensitive to the angle of incidence of the laser beam in the cell, which allows to vary the lineshape of the signal without changing the parameters of the laser (intensity, frequency, ...) or atomic vapor. Out of resonance with the atomic vapor, the parallel windows of commercial optical cell cavity works as a low finesse Fabry-Pérot with a free spectral range of 150 GHz. However, in resonance, the optical path of the cavity changes varies with frequency due to the dispersive response of the atomic vapor. This study experimentally characterized the transmission signal through a cavity containing resonant vapor as a function of intensity and frequency of the laser, as well as its dependence on the angle of incidence of the beam. A numerical model that allows to determine the collisional broadening of the atomic vapor adjusting the spectral curves of the transmission signal was developed. As an application, exploring the oscillations in the wings of the resonance, we can lock the laser frequency at a few GHz off the center of the atomic resonance. The lock was performed in the frequency range between 0,8 GHz and 2,4 GHz from the center of the D2 line of cesium. To characterize the locking stability we measure the optical beat signal between two similar experiments, using the same locking technique.