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Tuning from enhanced absorption to transparency in the Hanle effect

Harish Ravi, Sapam Ranjita Chanu, Vasant Natarajan A

Published Oct 13, 2015• 0 citations
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Abstract

We demonstrate that the Hanle effect can be tuned from enhanced absorption to enhanced transmission simply by changing the polarization of the laser beam from linear to circular. The experiments are done on the D$_2$ line of Cs at 852 nm, using the closed hyperfine transition $ F_g = 4 \rightarrow F_e = 5 $. The transformation can be understood qualitatively based on optical pumping and coherences among the magnetic sublevels of the levels involved. To increase the coherence time, the experiments done in a paraffin-coated Cs vapor cell (at room temperature). The observed linewidth is extremely narrow (about 1 mG or 175 Hz), making this a promising technique for all kinds of precision measurements.

Related papers

Polarization-dependent tuning of the Hanle effect in the ground state of Cs

Harish Ravi, Mangesh Bhattarai, Vineet Bharti +1 more

We demonstrate that the Hanle effect can be tuned between magnetically induced absorption (MIA) and magnetically induced transmission (MIT) simply by changing the polarization of the input laser beam.The experiments are done using closed hyperfine transitions of the D2 line of 133 Cs -Fg = 3 → Fe = 2 and Fg = 4 → Fe = 5.The former shows a transformation from MIT to MIA, while the latter shows the opposite behavior.A qualitative explanation based on optical pumping and coherences among the magnetic sublevels of the ground state is borne out by a detailed density-matrix calculation.To increase the coherence time, the experiments are done in a Cs vapor cell with paraffin coating on the walls.The observed linewidth is extremely narrow (∼ 0.1 mG) compared to previous work in this area, making this a promising technique for all kinds of precision measurements.

arXiv:1510.06058•Europhysics Letters (EPL)•Mar 1, 2017•16 citations

Polarization-dependent tuning of the Hanle effect in the ground state of Cs

Harish Ravi, Mangesh Bhattarai, Vineet Bharti +1 more

We demonstrate that the Hanle effect can be tuned between magnetically induced absorption (MIA) and magnetically induced transmission (MIT) simply by changing the polarization of the input laser beam. The experiments are done using closed hyperfine transitions of the D-2 line of Cs-133 - Fg = 3 -> F-e = 2 and F-g = 4 -> Fe = 5. The former shows a transformation from MIT to MIA, while the latter shows the opposite behavior. A qualitative explanation based on optical pumping and coherences among the magnetic sublevels of the ground state is borne out by a detailed density- matrix calculation. To increase the coherence time, the experiments are done in a C-s vapor cell with paraffin coating on the walls. The observed linewidth is extremely narrow (similar to 0.1mG) compared to previous work in this area, making this a promising technique for all kinds of precision measurements. Copyright (C) EPLA, 2017

•Jan 1, 2017•16 citations

Tuning of the Hanle effect from EIT to EIA using spatially separated probe and control beams

Mangesh Bhattarai, Vineet Bharti, Vasant Natarajan A

Abstract We demonstrate a technique for continuous tuning of the Hanle effect from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) by changing the polarization ellipticity of a control beam. In contrast to previous work in this field, we use spatially separated probe and control beams. The experiments are done using magnetic sublevels of the Fg = 4 → Fe = 5 closed hyperfine transition in the 852 nm D2 line of 133Cs. The atoms are contained in a room temperature vapor cell with anti-relaxation (paraffin) coating on the walls. The paraffin coating is necessary for the atomic coherence to be transported between the beams. The experimental results are supported by a density-matrix analysis of the system, which also explains the observed amplitude and zero-crossing of the resonances. Such continuous tuning of the sign of a resonance has important applications in quantum memory and other precision measurements.

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Level-crossing resonances on open atomic transitions in a buffered Cs vapor cell: Linewidth narrowing, high contrast, and atomic magnetometry applications

Denis V. Brazhnikov, V. I. Vishnyakov, Andrei Goncharov +3 more

The ground-state Hanle effect (GSHE) in alkali-metal atomic vapor using a single circularly polarized light wave underlies one of the most reliable and simple techniques of modern atomic magnetometry. This effect causes a narrow (subnatural-width) resonance in the light wave intensity passing through the vapor cell. The GSHE-based sensors typically operate in the so-called spin-exchange relaxation-free (SERF) regime to reduce the resonance linewidth. However, this regime requires a relatively high temperature of vapors (approximately equal to $150{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$), leading to high heat release and power consumption of the sensor head. In addition, without applying special measures, the SERF regime significantly limits the dynamic range of measurements. Here we study a pump-probe scheme involving a single elliptically polarized light wave and a polarimetric detection technique. The wave is in resonance with two adjacent optical transitions in the cesium ${D}_{1}$ line ($\ensuremath{\lambda}\phantom{\rule{0.16em}{0ex}}\ensuremath{\approx}\phantom{\rule{0.16em}{0ex}}894.5$ nm) due to their overlap in the presence of a buffer gas (130 Torr neon). Using a small ($V\ensuremath{\approx}0.1\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}$) glass vapor cell, we demonstrate the possibility to observe subnatural-width resonances with a high contrast-to-width ratio (up to 45%/mG) in low-temperature ($60{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$) operation due to strong light-induced circular dichroism in the medium. Based on the $\mathrm{\ensuremath{\Lambda}}$ scheme of atomic energy levels, we obtain explicit analytical expressions for the shape of the resonance line. The model reveals a linewidth narrowing effect due to openness of the level scheme. The observed bright features are unusual for magneto-optical atomic spectroscopy as openness is commonly considered to be an undesirable effect that degrades resonance characteristics. Measuring the noise voltage, we estimate the sensitivity of the magnetic-field measurements to be 1.8 $\mathrm{pT}/\sqrt{\mathrm{Hz}}$ with a sensitivity of 60 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ in the photon-shot-noise limit. In general, the results contribute to the theory of GSHE resonances and also can be applied to development of a low-temperature high-sensitivity miniaturized magnetic-field sensor with an extended dynamic range.

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Measurement of longitudinal and transverse spin relaxation rates using the ground-state Hanle effect

N. Castagna, Antoine Weis

We present a theoretical and experimental study of the resonant circularly-polarized-light-induced Hanle effect in the ground state of Cs vapor atoms in a paraffin-coated cell. The effect manifests itself as a narrow resonance (centered at $B=0$) in the dependence of the optical transmission coefficient of the vapor on the magnitude of an external magnetic field $\stackrel{P\vec}{B}$. We develop a theoretical model that yields an algebraic expression for the shape of these resonances for arbitrary field orientations and arbitrary angular momenta of the states coupled by the exciting light, provided that the light power is kept sufficiently small. An experimental procedure for assessing the range of validity of the model is given. Experiments were carried out on the laser-driven Cs ${D}_{1}$ transition both in longitudinal and transverse field geometries, and the observed line shapes of the corresponding bright and dark resonances give an excellent confirmation of the model predictions. The method is applied for determining the intrinsic longitudinal and transverse relaxation rates of the vector magnetization in the vapor and their dependence on light power.

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Enhanced absorption Hanle effect in the configuration of crossed laser beam and magnetic field

Ferruccio Renzoni, S. Cartaleva, G. Alzetta +1 more

We analyze the Hanle effect on the closed Fg equals 3 yields Fe equals 4 D2-line transition of 85Rb, by both numerical solutions of the optical Bloch equations and by experimental investigations on cell containing rubidium vapor. For laser radiation with linear polarization orthogonal to the applied magnetic field, the Hanle signal is characterized by narrow bright resonances at low laser intensities. A bright resonance Hanle signal is obtained also exciting the rubidium atoms by circularly polarized laser light and scanning a transversely applied magnetic field, at different values of an applied longitudinal magnetic field. We report experimental and numerical evidence of this new bright resonance.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 9, 2001•0 citations
We demonstrate that the Hanle effect can be tuned from enhanced absorption to enhanced transmission simply by changing the polarization of the laser beam from linear to circular. The experiments are done on the D2_22​ line of Cs at 852 nm, using the closed hyperfine transition Fg=4→Fe=5F_g = 4 \rightarrow F_e = 5Fg​=4→Fe​=5. The transformation can be understood qualitatively based on optical pumping and coherences among the magnetic sublevels of the levels involved. To increase the coherence time, the experiments done in a paraffin-coated Cs vapor cell (at room temperature). The observed linewidth is extremely narrow (about 1 mG or 175 Hz), making this a promising technique for all kinds of precision measurements.
We demonstrate that the Hanle effect can be tuned between magnetically induced absorption (MIA) and magnetically induced transmission (MIT) simply by changing the polarization of the input laser beam.The experiments are done using closed hyperfine transitions of the D2 line of 133 Cs -Fg = 3 → Fe = 2 and Fg = 4 → Fe = 5.The former shows a transformation from MIT to MIA, while the latter shows the opposite behavior.A qualitative explanation based on optical pumping and coherences among the magnetic sublevels of the ground state is borne out by a detailed density-matrix calculation.To increase the coherence time, the experiments are done in a Cs vapor cell with paraffin coating on the walls.The observed linewidth is extremely narrow (∼ 0.1 mG) compared to previous work in this area, making this a promising technique for all kinds of precision measurements.
We demonstrate that the Hanle effect can be tuned between magnetically induced absorption (MIA) and magnetically induced transmission (MIT) simply by changing the polarization of the input laser beam. The experiments are done using closed hyperfine transitions of the D-2 line of Cs-133 - Fg = 3 -> F-e = 2 and F-g = 4 -> Fe = 5. The former shows a transformation from MIT to MIA, while the latter shows the opposite behavior. A qualitative explanation based on optical pumping and coherences among the magnetic sublevels of the ground state is borne out by a detailed density- matrix calculation. To increase the coherence time, the experiments are done in a C-s vapor cell with paraffin coating on the walls. The observed linewidth is extremely narrow (similar to 0.1mG) compared to previous work in this area, making this a promising technique for all kinds of precision measurements. Copyright (C) EPLA, 2017
Abstract We demonstrate a technique for continuous tuning of the Hanle effect from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) by changing the polarization ellipticity of a control beam. In contrast to previous work in this field, we use spatially separated probe and control beams. The experiments are done using magnetic sublevels of the Fg = 4 → Fe = 5 closed hyperfine transition in the 852 nm D2 line of 133Cs. The atoms are contained in a room temperature vapor cell with anti-relaxation (paraffin) coating on the walls. The paraffin coating is necessary for the atomic coherence to be transported between the beams. The experimental results are supported by a density-matrix analysis of the system, which also explains the observed amplitude and zero-crossing of the resonances. Such continuous tuning of the sign of a resonance has important applications in quantum memory and other precision measurements.
The ground-state Hanle effect (GSHE) in alkali-metal atomic vapor using a single circularly polarized light wave underlies one of the most reliable and simple techniques of modern atomic magnetometry. This effect causes a narrow (subnatural-width) resonance in the light wave intensity passing through the vapor cell. The GSHE-based sensors typically operate in the so-called spin-exchange relaxation-free (SERF) regime to reduce the resonance linewidth. However, this regime requires a relatively high temperature of vapors (approximately equal to $150{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$), leading to high heat release and power consumption of the sensor head. In addition, without applying special measures, the SERF regime significantly limits the dynamic range of measurements. Here we study a pump-probe scheme involving a single elliptically polarized light wave and a polarimetric detection technique. The wave is in resonance with two adjacent optical transitions in the cesium D1{D}_{1}D1​ line ($\ensuremath{\lambda}\phantom{\rule{0.16em}{0ex}}\ensuremath{\approx}\phantom{\rule{0.16em}{0ex}}894.5$ nm) due to their overlap in the presence of a buffer gas (130 Torr neon). Using a small ($V\ensuremath{\approx}0.1\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{3}$) glass vapor cell, we demonstrate the possibility to observe subnatural-width resonances with a high contrast-to-width ratio (up to 45%/mG) in low-temperature ($60{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$) operation due to strong light-induced circular dichroism in the medium. Based on the $\mathrm{\ensuremath{\Lambda}}$ scheme of atomic energy levels, we obtain explicit analytical expressions for the shape of the resonance line. The model reveals a linewidth narrowing effect due to openness of the level scheme. The observed bright features are unusual for magneto-optical atomic spectroscopy as openness is commonly considered to be an undesirable effect that degrades resonance characteristics. Measuring the noise voltage, we estimate the sensitivity of the magnetic-field measurements to be 1.8 pT/Hz\mathrm{pT}/\sqrt{\mathrm{Hz}}pT/Hz​ with a sensitivity of 60 fT/Hz\mathrm{fT}/\sqrt{\mathrm{Hz}}fT/Hz​ in the photon-shot-noise limit. In general, the results contribute to the theory of GSHE resonances and also can be applied to development of a low-temperature high-sensitivity miniaturized magnetic-field sensor with an extended dynamic range.
We present a theoretical and experimental study of the resonant circularly-polarized-light-induced Hanle effect in the ground state of Cs vapor atoms in a paraffin-coated cell. The effect manifests itself as a narrow resonance (centered at B=0B=0B=0) in the dependence of the optical transmission coefficient of the vapor on the magnitude of an external magnetic field $\stackrel{P\vec}{B}$. We develop a theoretical model that yields an algebraic expression for the shape of these resonances for arbitrary field orientations and arbitrary angular momenta of the states coupled by the exciting light, provided that the light power is kept sufficiently small. An experimental procedure for assessing the range of validity of the model is given. Experiments were carried out on the laser-driven Cs D1{D}_{1}D1​ transition both in longitudinal and transverse field geometries, and the observed line shapes of the corresponding bright and dark resonances give an excellent confirmation of the model predictions. The method is applied for determining the intrinsic longitudinal and transverse relaxation rates of the vector magnetization in the vapor and their dependence on light power.
We analyze the Hanle effect on the closed Fg equals 3 yields Fe equals 4 D2-line transition of 85Rb, by both numerical solutions of the optical Bloch equations and by experimental investigations on cell containing rubidium vapor. For laser radiation with linear polarization orthogonal to the applied magnetic field, the Hanle signal is characterized by narrow bright resonances at low laser intensities. A bright resonance Hanle signal is obtained also exciting the rubidium atoms by circularly polarized laser light and scanning a transversely applied magnetic field, at different values of an applied longitudinal magnetic field. We report experimental and numerical evidence of this new bright resonance.