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Laser Physics

Multichannel laser-induced fluorescence in rubidium and residual cesium hot atomic vapours

Armen D. Sargsyan, Anahit L. Gogyan, David G. Sarkisyan

Published Aug 17, 2026• 0 citations
Publisher

Abstract

Abstract Laser-induced fluorescence (LIF) in the spectral range of 400–1000 nm has been investigated in rubidium vapor excited by narrowband diode laser radiation at 780 nm and 795 nm, resonant with the 5 S 1 / 2 → 5 P 1 / 2 , 3 / 2 transitions. Experiments were performed using three specially fabricated all-sapphire cells with thicknesses of L = 1 cm, 10 μ m, and 500 nm. Multiple fluorescence channels were observed, and it is shown that many LIF signals are suppressed with decreasing cell thickness due to enhanced atom–wall collisions leading to quenching of excited states. Nevertheless, for a nanocell of thickness L = 500 nm at temperatures of ∼ 300 ∘ C, blue fluorescence at 420 nm remains observable, and its intensity is compared with results available in the literature. It is further demonstrated that LIF spectroscopy enables detection and estimation of residual cesium vapor in rubidium cells via energy-transfer processes. In addition, the Rb vapor cell can operate as an efficient optical filter and frequency up-converter, converting radiation at 780 nm or 795 nm into shorter wavelengths, notably 420 nm. These results highlight the potential of broadband LIF spectroscopy in alkali vapors for applications in precision measurements, optical frequency standards, and quantum technologies.

DOI
10.1088/1555-6611/ae95e8

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New experimental results and new phenomena related to the study of the retrofluorescence spectrum induced by a diode laser at the interface between glass and cesium vapor are presented. The Cs 62P3/2(Fe) hyperfine states are populated with a low-intensity tunable diode laser with a 10-MHz spectral bandwidth. We report an integrated atomic retrofluorescence spectrum in the 852.2-nm (62P3/2–62S1/2) resonance line and 917.2-nm (62D5/2–62P3/2) line generated by energy-pooling collisions. Emission spectra of the molecular fluorescence signal have been observed. At the resonance line a large proportion of the atoms excited by the laser are located in the vicinity of the surface. The interactions between the excited atomic 62P3/2 state and the surface appear as a spectral inhibition of the integrated retrofluorescence spectrum for both the atomic line and the molecular band. This spectral inhibition indicates that the nonradiative transformation process of changing atomically excited energy into thermal energy is preferred. We report the analysis of the dominant processes in the vicinity of the 852.2-nm resonance line, which can influence the retrofluorescence hyperfine spectrum at the boundary between the glass window and the saturated cesium vapor. Only the nonradiative transfer by evanescent waves toward the dissipative surface is retained. Using this mechanism, we formulate, for the first time to our knowledge, a simple model of a backscattered hyperfine fluorescence signal. The glass–vapor interface is considered as two distinct regions: a wavelength-thickness vapor layer joined to the surface and a more remote vapor region. The first region is analyzed as a spectral filter that annihilates the absorbed photons and the second one as a rich spectral light source. The experimental setup is described, and measured integrated retrofluorescence spectra are compared with predictions made by the model. The consistency between theory and experiment is remarkably good considering that the model depends only on two unknown parameters: the nonradiative transfer rate and the absorption shape line of the filtering region.

Journal of the Optical Society of America B•Nov 1, 2001•15 citations
Abstract Laser-induced fluorescence (LIF) in the spectral range of 400–1000 nm has been investigated in rubidium vapor excited by narrowband diode laser radiation at 780 nm and 795 nm, resonant with the 5 S 1 / 2 → 5 P 1 / 2 , 3 / 2 transitions. Experiments were performed using three specially fabricated all-sapphire cells with thicknesses of L = 1 cm, 10 μ m, and 500 nm. Multiple fluorescence channels were observed, and it is shown that many LIF signals are suppressed with decreasing cell thickness due to enhanced atom–wall collisions leading to quenching of excited states. Nevertheless, for a nanocell of thickness L = 500 nm at temperatures of ∼ 300 ∘ C, blue fluorescence at 420 nm remains observable, and its intensity is compared with results available in the literature. It is further demonstrated that LIF spectroscopy enables detection and estimation of residual cesium vapor in rubidium cells via energy-transfer processes. In addition, the Rb vapor cell can operate as an efficient optical filter and frequency up-converter, converting radiation at 780 nm or 795 nm into shorter wavelengths, notably 420 nm. These results highlight the potential of broadband LIF spectroscopy in alkali vapors for applications in precision measurements, optical frequency standards, and quantum technologies.
Laser-induced fluorescence (LIF) was studied in the 400–1000 nm wavelength range using narrow-band 852 nm laser radiation resonant with Cs atomic 6S1/2 → 6P3/2 transition. T-shaped cells made entirely of technical sapphire with thicknesses of L = 1 cm, 40 μm, and ~400 nm, containing cesium atomic vapor, were used. It was shown that with the cell thickness decrease (from centimeters to nanometer thicknesses), many LIF signals are suppressed due to an increase in the number of atomic collisions with the walls, leading to quenching of excited states. By recording the LIF signal, it is also possible to estimate the amount of residual Rb atomic vapor (if any exists) in the Cs-containing cell. The Cs vapor cell can serve as an efficient optical frequency converter filter and has other applications.
Laser-induced fluorescence (LIF) was studied in the 400–1000 nm wavelength range using narrow-band 852 nm laser radiation resonant with Cs atomic 6S1/2→6P3/2 transition. Tshaped cells made entirely of technical sapphire with thicknesses of L = 1 cm, 40 μm, and ~400 nm, containing cesium atomic vapor, were used. It was shown that with decreasing cell thickness (from centimeter to nanometer thicknesses), many LIF signals are suppressed due to an increase in the number of atomic collisions with the walls, leading to quenching of excited states. By recording the LIF signal, it is also possible to estimate the amount of residual Rb atomic vapor (if any exists) in the Cs-containing cell. The Cs vapor cell can serve as an efficient optical frequency converter filter and have also other applications.
We have observed laser-induced fluorescence using 456 nm laser radiation, resonant with the 6S1/2-7P3/2 transition in Cs atoms. It includes red emission lines in the range of 580-730 nm and a prominent line at 852 nm corresponding to the 6P3/2-6S1/2 transition. A T-shaped all-sapphire cell with a length of 1 cm, containing Cs atomic vapor and capable of being heated up to 500 oC, was used. The laser-induced fluorescence (LIF) power at 852 nm was investigated as a function of the cell temperature. The maximum LIF power was achieved at 130 oC, while a significant decrease was observed around 300 oC. At 130 oC, the Doppler-broadened LIF spectrum at 852 nm exhibited self-conversion, resulting in the formation of two distinct peaks within the spectrum. The LIF power at 852 nm was also studied as a function of the 456 nm radiation power. The Cs cell demonstrated potential as an efficient optical filter and down-converter, effectively transforming 456 nm radiation into 852 nm radiation.
In the sealed-off cesium vapor cell studied in this work, a residual rubidium fraction of approximately $\sim1%wasobserved.WeinvestigatetheopticalresponseofthesetraceRbatomsinasealed1 cmlongCs−filledvaporcell.Despitethelowconcentration,laserexcitationat795 nmallowstheobservationofsaturatedabsorptionandelectromagneticallyinducedtransparency(EIT)resonances.ThesurroundingCsvaporeffectivelyactsasabuffermedium,reducingtheRbatomicvelocityandincreasingtheinteractiontimewiththelaserfield,whichimprovestheEITsignal.Theexperimentsareperformedinanall−sapphirecellthatcanbeheatedupto5001\% was observed. We investigate the optical response of these trace Rb atoms in a sealed 1~cm long Cs-filled vapor cell. Despite the low concentration, laser excitation at 795~nm allows the observation of saturated absorption and electromagnetically induced transparency (EIT) resonances. The surrounding Cs vapor effectively acts as a buffer medium, reducing the Rb atomic velocity and increasing the interaction time with the laser field, which improves the EIT signal. The experiments are performed in an all-sapphire cell that can be heated up to 5001%wasobserved.WeinvestigatetheopticalresponseofthesetraceRbatomsinasealed1 cmlongCs−filledvaporcell.Despitethelowconcentration,laserexcitationat795 nmallowstheobservationofsaturatedabsorptionandelectromagneticallyinducedtransparency(EIT)resonances.ThesurroundingCsvaporeffectivelyactsasabuffermedium,reducingtheRbatomicvelocityandincreasingtheinteractiontimewiththelaserfield,whichimprovestheEITsignal.Theexperimentsareperformedinanall−sapphirecellthatcanbeheatedupto500^{\circ}$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.
Abstract Using laser radiation with a wavelength of 852 nm, which is in resonance with Cs atoms, the bright laser-induced fluorescence (LIF) on the blue lines of 456 and 459 nm (transitions 6S1/2 → 7P3/2 and 6S1/2 → 7 P1/2) was studied by the transition 6S1/2 → 6P3/2. A 1 cm long T-shaped sapphire cell containing Cs atomic vapors was used. The LIF power was investigated as a function of the cell temperature. A linear dependence of the LIF power on the pump radiation was observed. The LIF reached a maximum at 100°C. It is shown that the Cs cell can serve as an effective optical up-converter filter of radiation with a wavelength of 852 nm to radiation with a wavelength of 456 nm.
New experimental results and new phenomena related to the study of the retrofluorescence spectrum induced by a diode laser at the interface between glass and cesium vapor are presented. The Cs 62P3/2(Fe) hyperfine states are populated with a low-intensity tunable diode laser with a 10-MHz spectral bandwidth. We report an integrated atomic retrofluorescence spectrum in the 852.2-nm (62P3/2–62S1/2) resonance line and 917.2-nm (62D5/2–62P3/2) line generated by energy-pooling collisions. Emission spectra of the molecular fluorescence signal have been observed. At the resonance line a large proportion of the atoms excited by the laser are located in the vicinity of the surface. The interactions between the excited atomic 62P3/2 state and the surface appear as a spectral inhibition of the integrated retrofluorescence spectrum for both the atomic line and the molecular band. This spectral inhibition indicates that the nonradiative transformation process of changing atomically excited energy into thermal energy is preferred. We report the analysis of the dominant processes in the vicinity of the 852.2-nm resonance line, which can influence the retrofluorescence hyperfine spectrum at the boundary between the glass window and the saturated cesium vapor. Only the nonradiative transfer by evanescent waves toward the dissipative surface is retained. Using this mechanism, we formulate, for the first time to our knowledge, a simple model of a backscattered hyperfine fluorescence signal. The glass–vapor interface is considered as two distinct regions: a wavelength-thickness vapor layer joined to the surface and a more remote vapor region. The first region is analyzed as a spectral filter that annihilates the absorbed photons and the second one as a rich spectral light source. The experimental setup is described, and measured integrated retrofluorescence spectra are compared with predictions made by the model. The consistency between theory and experiment is remarkably good considering that the model depends only on two unknown parameters: the nonradiative transfer rate and the absorption shape line of the filtering region.