Doppler broadening presents a major limitation for high-resolution spectroscopy and nonlinear optics in room-temperature atomic vapors. Here, we demonstrate the suppression of Doppler broadening accompanied by pronounced absorption on the upper transition of a three-level ladder system, achieved by dressing the intermediate state with a strong control field. As a concrete realization, we study a hot vapor of $^{87}$ Rb where the lower transition is driven by a strong control field resonant with the D2 line at a wavelength of 780 nm, while a weak counter-propagating probe field at the telecom C-band wavelength of 1529 nm ( $5P_{(3/2)}\leftrightarrow 4D_{(5/2)}$ ) interrogates the dressed states. We observe absorption features with a resonant optical depth of approximately 4 and a full width at half maximum of about 17 MHz. Remarkably, this corresponds to an order-of-magnitude reduction relative to the Doppler width, while the optical depth on the upper transition of the ladder scheme exceeds that of the Doppler-broadened lower transition. The measured spectra are in good agreement with theoretical modeling. Combining high optical density with sub-Doppler-width absorption lines typically requires laser-cooled atoms, while our approach profits from the experimental simplicity of a hot-vapor platform.Doppler broadening presents a major limitation for high-resolution spectroscopy and nonlinear optics in room-temperature atomic vapors. Here, we demonstrate the suppression of Doppler broadening accompanied by pronounced absorption on the upper transition of a three-level ladder system, achieved by dressing the intermediate state with a strong control field. As a concrete realization, we study a hot vapor of $^{87}$Rb where the lower transition is driven by a strong control field resonant with the D2 line at a wavelength of 780 nm, while a weak counter-propagating probe field at the telecom C-band wavelength of 1529 nm ($5P_{(3/2)}\leftrightarrow 4D_{(5/2)}$) interrogates the dressed states. We observe absorption features with a resonant optical depth of approximately 4 and a full width at half maximum of about 17 MHz. Remarkably, this corresponds to an order-of-magnitude reduction relative to the Doppler width, while the optical depth on the upper transition of the ladder scheme exceeds that of the Doppler-broadened lower transition. The measured spectra are in good agreement with theoretical modeling. Combining high optical density with sub-Doppler-width absorption lines typically requires laser-cooled atoms, while our approach profits from the experimental simplicity of a hot-vapor platform.

physics.atom-phCross-listedarXiv:2603.09003Physical Review AMar 11, 20260 citations

High-resolution four-wave-mixing spectroscopy of collision-induced narrow resonances in Doppler-broadened systems

Jing Liu, Duncan G. Steel

We report a series of measurements of the nearly degenerate four-wave-mixing response in atomic sodium in the presence of a helium buffer gas. The results show the line shape associated with both the ground-state and excited-state dynamics. The line shape evolves as a function of pressure from a dip at a pressure of 0 Torr to a spike at a few Torr due to the presence of collisions. The width of the spike is determined by residual Doppler broadening. At higher pressure (\ensuremath{\ge}10 Torr), the width of the spike is further narrowed below the residual Doppler width. The additional reduction is due to a form of Dicke narrowing associated with the dynamics of the lower- and upper-level excitations. The results are in qualitative agreement with a perturbation solution of the density-matrix equations which include the effects of velocity-changing collisions and state-changing collisions.We report a series of measurements of the nearly degenerate four-wave-mixing response in atomic sodium in the presence of a helium buffer gas. The results show the line shape associated with both the ground-state and excited-state dynamics. The line shape evolves as a function of pressure from a dip at a pressure of 0 Torr to a spike at a few Torr due to the presence of collisions. The width of the spike is determined by residual Doppler broadening. At higher pressure (\ensuremath{\ge}10 Torr), the width of the spike is further narrowed below the residual Doppler width. The additional reduction is due to a form of Dicke narrowing associated with the dynamics of the lower- and upper-level excitations. The results are in qualitative agreement with a perturbation solution of the density-matrix equations which include the effects of velocity-changing collisions and state-changing collisions.

Physical Review ANov 1, 19885 citations

Doppler narrowing of EIT linewidth in closed-loop systems

Nawaz Sarif Mallick, Kanhaiya Pandey

PramanaJun 19, 202011 citations

Pulling of the emission frequency of an injection laser by Doppler-free absorption resonances in an intracavity cell

A. M. Akulshin, Motoichi Ohtsu

Optical frequency locking of two injection lasers was achieved with the aid of a Doppler-free absorption resonance, as the result of simultaneous interaction of radiations from two lasers with rubidium vapour inside an intracavity cell. Narrowing of the emission line width by a factor of 8 and a reduction in the frequency noise by 15 dB were achieved in a band up to 350 kHz. A nonlinear frequency pulling by a resonance of coherent population trapping in an intracavity cell was demonstrated for the first time.Optical frequency locking of two injection lasers was achieved with the aid of a Doppler-free absorption resonance, as the result of simultaneous interaction of radiations from two lasers with rubidium vapour inside an intracavity cell. Narrowing of the emission line width by a factor of 8 and a reduction in the frequency noise by 15 dB were achieved in a band up to 350 kHz. A nonlinear frequency pulling by a resonance of coherent population trapping in an intracavity cell was demonstrated for the first time.

Quantum ElectronicsJul 31, 19945 citations

Compensating Doppler broadening with light-shifts

Claude N. Cohen-Tannoudji, F. Hoffbeck, Serge Reynaud

Optics CommunicationsOct 1, 197827 citations

^{87}

Rb where the lower transition is driven by a strong control field resonant with the D2 line at a wavelength of 780 nm, while a weak counter-propagating probe field at the telecom C-band wavelength of 1529 nm (

5P_{(3/2)}\leftrightarrow 4D_{(5/2)}

) interrogates the dressed states. We observe absorption features with a resonant optical depth of approximately 4 and a full width at half maximum of about 17 MHz. Remarkably, this corresponds to an order-of-magnitude reduction relative to the Doppler width, while the optical depth on the upper transition of the ladder scheme exceeds that of the Doppler-broadened lower transition. The measured spectra are in good agreement with theoretical modeling. Combining high optical density with sub-Doppler-width absorption lines typically requires laser-cooled atoms, while our approach profits from the experimental simplicity of a hot-vapor platform.