The hyperfine Paschen-Back Faraday effect

We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen–Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive index. Fitting to the atomic spectra, we achieve magnetic field sensitivity at the 10 −4 level. Finally we note that the Faraday signal shows zero crossings which can be used as temperature insensitive error signals for laser frequency stabilization at large detuning. The theoretical sensitivity for 87 Rb is found to be ∼40 kHz °C −1 .We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen–Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive index. Fitting to the atomic spectra, we achieve magnetic field sensitivity at the 10 −4 level. Finally we note that the Faraday signal shows zero crossings which can be used as temperature insensitive error signals for laser frequency stabilization at large detuning. The theoretical sensitivity for 87 Rb is found to be ∼40 kHz °C −1 .

arXiv:1401.1659Journal of Physics B Atomic Molecular and Optical PhysicsMar 26, 201456 citations

Absolute absorption and dispersion of a rubidium vapour in the hyperfine Paschen-Back regime

Weller, L, Kleinbach, KS, Zentile, MA +4 more

Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen–Back regime for fields greater than 0.33 T on the Rb D2 line. The experiment uses a compact 1 mm3 microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen–Back regime for fields greater than 0.33 T on the Rb D2 line. The experiment uses a compact 1 mm3 microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.

Nov 14, 201244 citations

Applications of the Faraday effect in hot atomic vapours

Mark A. Zentile

This thesis presents both a computational and experimental investigation into light propagation in hot alkali-metal vapours, with a particular focus on utilizing the Faraday effect for practical applications. A model to calculate various spectra for a weak-probe laser beam in an atomic medium with an applied axial magnetic field is presented. A computer program (ElecSus) was developed which implements this model efficiently. Using ElecSus we design optical devices such as Faraday filters and laser frequency stabilizing references. The design of Faraday filters utilizing compact vapour cells is shown, along with excellent agreement with experiment. The importance of including the effect of self broadening in the model is shown for these short path length vapour cells. Also, a Faraday filter is presented that can potentially be used for quantum optics experiments on the caesium D $_1$ line (894~nm). The filter displays the highest ratio of transmission to equivalent noise bandwidth to date for a linear Faraday filter, demonstrating the power of computerized optimization for this application. Furthermore, a Faraday filter is presented for use as an intra-cavity element in an external-cavity diode laser. A proof-of-principle experiment is demonstrated which shows that using a short external cavity with the Faraday filter eliminates mode-hops. Experimentally and theoretically the Faraday effect is investigated in large magnetic fields where alkali-metal atoms enter the hyperfine Paschen-Back regime. This hyperfine Paschen-Back Faraday effect is shown to allow a direct measure of the refractive indices for left and right circular polarized light. Furthermore, fitting the weak-probe spectra using ElecSus is found to give measures of the magnetic field with a fractional precision of the order of $10^{-4}$ . In addition we study slow-light pulse propagation in a high density rubidium vapour, showing that our theoretical model for the electric susceptibility is valid for short pulses as well as continuous-wave light. This shows that the model is accurate for predicting weak-probe pulse propagation.This thesis presents both a computational and experimental investigation into light propagation in hot alkali-metal vapours, with a particular focus on utilizing the Faraday effect for practical applications. A model to calculate various spectra for a weak-probe laser beam in an atomic medium with an applied axial magnetic field is presented. A computer program (ElecSus) was developed which implements this model efficiently. Using ElecSus we design optical devices such as Faraday filters and laser frequency stabilizing references. The design of Faraday filters utilizing compact vapour cells is shown, along with excellent agreement with experiment. The importance of including the effect of self broadening in the model is shown for these short path length vapour cells. Also, a Faraday filter is presented that can potentially be used for quantum optics experiments on the caesium D$_1$ line (894~nm). The filter displays the highest ratio of transmission to equivalent noise bandwidth to date for a linear Faraday filter, demonstrating the power of computerized optimization for this application. Furthermore, a Faraday filter is presented for use as an intra-cavity element in an external-cavity diode laser. A proof-of-principle experiment is demonstrated which shows that using a short external cavity with the Faraday filter eliminates mode-hops. Experimentally and theoretically the Faraday effect is investigated in large magnetic fields where alkali-metal atoms enter the hyperfine Paschen-Back regime. This hyperfine Paschen-Back Faraday effect is shown to allow a direct measure of the refractive indices for left and right circular polarized light. Furthermore, fitting the weak-probe spectra using ElecSus is found to give measures of the magnetic field with a fractional precision of the order of $10^{-4}$. In addition we study slow-light pulse propagation in a high density rubidium vapour, showing that our theoretical model for the electric susceptibility is valid for short pulses as well as continuous-wave light. This shows that the model is accurate for predicting weak-probe pulse propagation.

Jan 1, 20154 citations

Absolute absorption and dispersion of a rubidium vapour in the hyperfine Paschen–Back regime

Lee Weller, Kathrin S Kleinbach, Mark A. Zentile +3 more

Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87 Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen–Back regime for fields greater than 0.33 T on the Rb D 2 line. The experiment uses a compact 1 mm 3 microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.Here we report on measurements of the absolute absorption and dispersion properties of an isotopically pure 87 Rb vapour for magnetic fields up to and including 0.6 T. We discuss the various regimes that arise when the hyperfine and Zeeman interactions have different magnitudes, and show that we enter the hyperfine Paschen–Back regime for fields greater than 0.33 T on the Rb D 2 line. The experiment uses a compact 1 mm 3 microfabricated vapour cell that makes it easy to maintain a uniform and large magnetic field with a small and inexpensive magnet. We find excellent agreement between the experimental results and numerical calculations of the weak probe susceptibility where the line positions and strengths are calculated by matrix diagonalization.

arXiv:1208.1879Journal of Physics B Atomic Molecular and Optical PhysicsOct 4, 201245 citations

Hyperfine Paschen–Back regime in alkali metal atoms: consistency of two theoretical considerations and experiment

Armen D. Sargsyan, G. Hakhumyan, Claude Leroy +4 more

Simple and efficient λ-method and λ/2-method (λ is the resonant wavelength of laser radiation) based on a nanometric-thickness cell filled with rubidium (Rb) are implemented to study the splitting of hyperfine transitions of an Rb85 and Rb87D1 line in an external magnetic field in the range of B=0.5–0.7 T. It is experimentally demonstrated from 20 (12) Zeeman transitions allowed at low B-field in Rb85 (Rb87) spectra in the case of σ+ polarized laser radiation, only 6 (4) remain at B>0.5 T, caused by decoupling of the total electronic momentum J and the nuclear spin momentum I (hyperfine Paschen–Back regime). The expressions derived in the frame of completely uncoupled basis (J,mJ;I,mI) describe the experimental results extremely well for Rb85 transitions at B>0.6 T (that is a manifestation of hyperfine Paschen–Back regime). A remarkable result is that the calculations based on the eigenstates of the coupled (F,mF) basis, which adequately describe the system for a low magnetic field, also predict reduction of the number of transition components from 20 to 6 for Rb85 and from 12 to 4 for Rb87 spectrum at B>0.5 T. Also, the Zeeman transition frequency shifts, frequency intervals between the components and their slope versus B, are in agreement with the experiment.Simple and efficient λ-method and λ/2-method (λ is the resonant wavelength of laser radiation) based on a nanometric-thickness cell filled with rubidium (Rb) are implemented to study the splitting of hyperfine transitions of an Rb85 and Rb87D1 line in an external magnetic field in the range of B=0.5–0.7 T. It is experimentally demonstrated from 20 (12) Zeeman transitions allowed at low B-field in Rb85 (Rb87) spectra in the case of σ+ polarized laser radiation, only 6 (4) remain at B>0.5 T, caused by decoupling of the total electronic momentum J and the nuclear spin momentum I (hyperfine Paschen–Back regime). The expressions derived in the frame of completely uncoupled basis (J,mJ;I,mI) describe the experimental results extremely well for Rb85 transitions at B>0.6 T (that is a manifestation of hyperfine Paschen–Back regime). A remarkable result is that the calculations based on the eigenstates of the coupled (F,mF) basis, which adequately describe the system for a low magnetic field, also predict reduction of the number of transition components from 20 to 6 for Rb85 and from 12 to 4 for Rb87 spectrum at B>0.5 T. Also, the Zeeman transition frequency shifts, frequency intervals between the components and their slope versus B, are in agreement with the experiment.

arXiv:1309.5775Journal of the Optical Society of America BApr 8, 201443 citations

Wide range linear magnetometer based on a sub-microsized K vapor cell

Marcis P. Auzinsh, Armen D. Sargsyan, A. Tonoyan +4 more

39 K atoms have the smallest ground state ( 2 S 1 / 2 ) hyperfine splitting of all the most naturally abundant alkali isotopes and, consequently, the smallest characteristic magnetic field value B 0 = A 2 S 1 / 2 / μ B ≈ 170 G , where A 2 S 1 / 2 is the ground state’s magnetic dipole interaction constant. In the hyperfine Paschen–Back regime ( B ≫ B 0 , where B is the magnitude of the external magnetic field applied on the atoms), only eight Zeeman transitions are visible in the absorption spectrum of the D 1 line of 39 K , while the probabilities of the remaining 16 Zeeman transitions tend to zero. In the case of 39 K , this behavior is reached already at relatively low magnetic field B > B 0 . For each circular polarization ( σ − , σ + ), four spectrally resolved atomic transitions having sub-Doppler widths are recorded using a sub-microsized vapor cell of thickness L = 120 − 390 n m . We present a method that allows to measure the magnetic field in the range of 0.1 − 10 k G with micrometer spatial resolution, which is relevant in particular for the determination of magnetic fields with large gradients (up to 3 G/µm). The theoretical model describes well the experimental results.39 K atoms have the smallest ground state ( 2 S 1 / 2 ) hyperfine splitting of all the most naturally abundant alkali isotopes and, consequently, the smallest characteristic magnetic field value B 0 = A 2 S 1 / 2 / μ B ≈ 170 G , where A 2 S 1 / 2 is the ground state’s magnetic dipole interaction constant. In the hyperfine Paschen–Back regime ( B ≫ B 0 , where B is the magnitude of the external magnetic field applied on the atoms), only eight Zeeman transitions are visible in the absorption spectrum of the D 1 line of 39 K , while the probabilities of the remaining 16 Zeeman transitions tend to zero. In the case of 39 K , this behavior is reached already at relatively low magnetic field B > B 0 . For each circular polarization ( σ − , σ + ), four spectrally resolved atomic transitions having sub-Doppler widths are recorded using a sub-microsized vapor cell of thickness L = 120 − 390 n m . We present a method that allows to measure the magnetic field in the range of 0.1 − 10 k G with micrometer spatial resolution, which is relevant in particular for the determination of magnetic fields with large gradients (up to 3 G/µm). The theoretical model describes well the experimental results.

arXiv:2203.11553Applied OpticsJun 17, 202214 citations

_1

line (894~nm). The filter displays the highest ratio of transmission to equivalent noise bandwidth to date for a linear Faraday filter, demonstrating the power of computerized optimization for this application. Furthermore, a Faraday filter is presented for use as an intra-cavity element in an external-cavity diode laser. A proof-of-principle experiment is demonstrated which shows that using a short external cavity with the Faraday filter eliminates mode-hops. Experimentally and theoretically the Faraday effect is investigated in large magnetic fields where alkali-metal atoms enter the hyperfine Paschen-Back regime. This hyperfine Paschen-Back Faraday effect is shown to allow a direct measure of the refractive indices for left and right circular polarized light. Furthermore, fitting the weak-probe spectra using ElecSus is found to give measures of the magnetic field with a fractional precision of the order of

10^{-4}

. In addition we study slow-light pulse propagation in a high density rubidium vapour, showing that our theoretical model for the electric susceptibility is valid for short pulses as well as continuous-wave light. This shows that the model is accurate for predicting weak-probe pulse propagation.