Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Review of Scientific Instruments

Design and characterization of a resonant microwave cavity as a diagnostic for ultracold plasmas

M. A. W. van Ninhuijs, K. A. Daamen, Job Beckers, O.J. Luiten

Published Jan 1, 2021• 7 citations
Publisher

Abstract

We present the design and commissioning of a resonant microwave cavity as a novel diagnostic for the study of ultracold plasmas. This diagnostic is based on the measurements of the shift in the resonance frequency of the cavity, induced by an ultracold plasma that is created from a laser-cooled gas inside. This method is simultaneously non-destructive, very fast (nanosecond temporal resolution), highly sensitive, and applicable to all ultracold plasmas. To create an ultracold plasma, we implement a compact magneto-optical trap based on a diffraction grating chip inside a 5 GHz resonant microwave cavity. We are able to laser cool and trap (7.25 ± 0.03) × 107 rubidium atoms inside the cavity, which are turned into an ultracold plasma by two-step pulsed (nanosecond or femtosecond) photo-ionization. We present a detailed characterization of the cavity, and we demonstrate how it can be used as a fast and sensitive probe to monitor the evolution of ultracold plasmas non-destructively. The temporal resolution of the diagnostic is determined by measuring the delayed frequency shift following femtosecond photo-ionization. We find a response time of 18 ± 2 ns, which agrees well with the value determined from the cavity quality factor and resonance frequency.

DOI
10.1063/5.0037846

Related papers

Collisional microwave heating and wall interaction of an ultracold plasma in a resonant microwave cavity

M. A. W. van Ninhuijs, Job Beckers, O.J. Luiten

Abstract Recently, we introduced a resonant microwave cavity as a diagnostic tool for the study of ultracold plasmas (UCPs). This diagnostic allows us to study the electron dynamics of UCPs non-destructively, very fast, and with high sensitivity by measuring the shift in the resonance frequency of a cavity, induced by a plasma. However, in an attempt to theoretically predict the frequency shift using a Gaussian self-similar expansion model, a three times faster plasma decay was observed in the experiment than found in the model. For this, we proposed two causes: plasma–wall interactions and collisional microwave heating. In this paper, we investigate the effect of both causes on the lifetime of the plasma. We present a simple analytical model to account for electrons being lost to the cavity walls. We find that the model agrees well with measurements performed on plasmas with different initial electron temperatures and that the earlier discrepancy can be attributed to electrons being lost to the walls. In addition, we perform measurements for different electric field strengths in the cavity and find that the electric field has a small, but noticeable effect on the lifetime of the plasma. By extending the model with the theory of collisional microwave heating, we find that this effect can be predicted quite well by treating the energy transferred from the microwave field to the plasma as additional initial excess energy for the electrons.

New Journal of Physics•Jun 1, 2022•4 citations

Microwave cavity resonance spectroscopy of ultracold plasmas

M. A. W. van Ninhuijs, K. A. Daamen, J. G. H. Franssen +4 more

We present an in situ study of the electron dynamics of an ultracold $^{85}\mathrm{Rb}$ plasma using microwave cavity resonance spectroscopy with submicrosecond temporal resolution and vastly improved sensitivity. We observe a three times faster plasma decay than predicted by a self-similar Gaussian expansion model, which might be attributed to collisional microwave heating and plasma-wall interactions. The demonstrated sensitivity enables nondestructive probing of other (nearly) ionized media of fundamental importance as well, such as cold Rydberg gases and antihydrogen plasmas.

Physical Review A•Dec 12, 2019•22 citations

Photoionization-cross-section measurement of the Rb85 5 P3/22 excited state using microwave cavity resonance spectroscopy

M. A. W. van Ninhuijs, Job Beckers, O.J. Luiten

We present microwave cavity resonance spectroscopy as a technique to determine excited-state photoionization cross sections of laser-cooled atoms. We demonstrate this technique by measuring the photoionization cross section of the $5^{2}P_{3/2}({F}^{\ensuremath{'}}=4)$ excited state of $^{85}\mathrm{Rb}$ to continuum by creating an ultracold plasma inside a 5-GHz resonant microwave cavity. We find a photoionization cross section of $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\phantom{\rule{4pt}{0ex}}{\mathrm{m}}^{2}$ for photon excess energies of 50, 100, 200, and 500 K above the ionization threshold. The measurements yield a cross section which is approximately 2 to 3 times smaller than the value provided by existing theory for the $5p$ excited state of $^{85}\mathrm{Rb}$ and two earlier measurements performed with other techniques for similar excess energies.

Physical Review A•Dec 23, 2022•0 citations

Single-atom detection on a chip: from realization to application

Alexander Stibor, H. Bender, S Kühnhold +3 more

In this paper, we describe the preparation and detection of ultracold atoms on a microchip with single-atom sensitivity. The detection scheme is based on multi-photon ionization of atoms and the subsequent guiding of the generated ions by ion optics to a channel electron multiplier. We resolve single atoms with a detection efficiency above 60%. The detector is suitable for real-time observations of static and dynamic processes in ultracold quantum gases. Although the ionization is destructive, sampling a small subset of the atomic distribution is sufficient for the determination of the desired information. We take full high-resolution spectra of ultracold atoms by ionizing only 5% of the atoms. Using an additional microwave near 6.8 GHz, the detection scheme becomes energy, position and state selective. This can be used for in situ determination of the energy distribution and temperature of atom clouds inside the trap and applied for future correlation measurements.

New Journal of Physics•Jun 28, 2010•15 citations

An additive-manufactured microwave cavity for a compact cold-atom clock

Etienne Batori, Alan Bregazzi, Ben Lewis +4 more

We present an additive-manufactured microwave cavity for a Ramsey-type, double resonance, compact cold-atom clock. Atoms can be laser cooled inside the cavity using a grating magneto-optic trap with the cavity providing an excellent TE011-like mode while maintaining sufficient optical access for atomic detection. The cavity features a low Q-factor of 360 which conveniently reduces the cavity pulling of the future clock. Despite the potential porosity of the additive-manufacturing process, we demonstrate that the cavity is well-suited for vacuum. A preliminary clock setup using cold atoms allows for measuring the Zeeman spectrum and Rabi oscillations in the cavity which enables us to infer excellent field uniformity and homogeneity, respectively, across the volume accessed by the cold atoms. Ramsey spectroscopy is demonstrated, indicating that the cavity is suitable for clock applications. Finally, we discuss the limitations of the future clock.

arXiv:2305.02898•Journal of Applied Physics•Jun 8, 2023•4 citations

Two-dimensional electronic spectroscopy of an ultracold gas

Friedemann Landmesser, Tobias Sixt, Katrin Dulitz +2 more

Femtosecond coherent multidimensional spectroscopy is demonstrated for an ultracold gas. A setup for phase modulation spectroscopy is used to probe the 3 2 S 1/2 –2 2 P 1/2,3/2 transition in an 800 μ K-cold sample of 7 Li atoms confined in a magneto-optical trap. The observation of a double quantum coherence response, a signature of interparticle interactions, paves the way for detailed investigations of few- and many-body effects in ultracold gases using this technique. The experiment combines a frequency resolution of 3 GHz with a potential time resolution of 200 fs, which allows for high-resolution studies of ultracold atoms and molecules both in the frequency and in the time domain.

arXiv:2210.03023•Optics Letters•Dec 5, 2022•9 citations
We present the design and commissioning of a resonant microwave cavity as a novel diagnostic for the study of ultracold plasmas. This diagnostic is based on the measurements of the shift in the resonance frequency of the cavity, induced by an ultracold plasma that is created from a laser-cooled gas inside. This method is simultaneously non-destructive, very fast (nanosecond temporal resolution), highly sensitive, and applicable to all ultracold plasmas. To create an ultracold plasma, we implement a compact magneto-optical trap based on a diffraction grating chip inside a 5 GHz resonant microwave cavity. We are able to laser cool and trap (7.25 ± 0.03) × 107 rubidium atoms inside the cavity, which are turned into an ultracold plasma by two-step pulsed (nanosecond or femtosecond) photo-ionization. We present a detailed characterization of the cavity, and we demonstrate how it can be used as a fast and sensitive probe to monitor the evolution of ultracold plasmas non-destructively. The temporal resolution of the diagnostic is determined by measuring the delayed frequency shift following femtosecond photo-ionization. We find a response time of 18 ± 2 ns, which agrees well with the value determined from the cavity quality factor and resonance frequency.
Abstract Recently, we introduced a resonant microwave cavity as a diagnostic tool for the study of ultracold plasmas (UCPs). This diagnostic allows us to study the electron dynamics of UCPs non-destructively, very fast, and with high sensitivity by measuring the shift in the resonance frequency of a cavity, induced by a plasma. However, in an attempt to theoretically predict the frequency shift using a Gaussian self-similar expansion model, a three times faster plasma decay was observed in the experiment than found in the model. For this, we proposed two causes: plasma–wall interactions and collisional microwave heating. In this paper, we investigate the effect of both causes on the lifetime of the plasma. We present a simple analytical model to account for electrons being lost to the cavity walls. We find that the model agrees well with measurements performed on plasmas with different initial electron temperatures and that the earlier discrepancy can be attributed to electrons being lost to the walls. In addition, we perform measurements for different electric field strengths in the cavity and find that the electric field has a small, but noticeable effect on the lifetime of the plasma. By extending the model with the theory of collisional microwave heating, we find that this effect can be predicted quite well by treating the energy transferred from the microwave field to the plasma as additional initial excess energy for the electrons.
We present an in situ study of the electron dynamics of an ultracold 85Rb^{85}\mathrm{Rb}85Rb plasma using microwave cavity resonance spectroscopy with submicrosecond temporal resolution and vastly improved sensitivity. We observe a three times faster plasma decay than predicted by a self-similar Gaussian expansion model, which might be attributed to collisional microwave heating and plasma-wall interactions. The demonstrated sensitivity enables nondestructive probing of other (nearly) ionized media of fundamental importance as well, such as cold Rydberg gases and antihydrogen plasmas.
We present microwave cavity resonance spectroscopy as a technique to determine excited-state photoionization cross sections of laser-cooled atoms. We demonstrate this technique by measuring the photoionization cross section of the $5^{2}P_{3/2}({F}^{\ensuremath{'}}=4)$ excited state of 85Rb^{85}\mathrm{Rb}85Rb to continuum by creating an ultracold plasma inside a 5-GHz resonant microwave cavity. We find a photoionization cross section of $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\phantom{\rule{4pt}{0ex}}{\mathrm{m}}^{2}$ for photon excess energies of 50, 100, 200, and 500 K above the ionization threshold. The measurements yield a cross section which is approximately 2 to 3 times smaller than the value provided by existing theory for the 5p5p5p excited state of 85Rb^{85}\mathrm{Rb}85Rb and two earlier measurements performed with other techniques for similar excess energies.
In this paper, we describe the preparation and detection of ultracold atoms on a microchip with single-atom sensitivity. The detection scheme is based on multi-photon ionization of atoms and the subsequent guiding of the generated ions by ion optics to a channel electron multiplier. We resolve single atoms with a detection efficiency above 60%. The detector is suitable for real-time observations of static and dynamic processes in ultracold quantum gases. Although the ionization is destructive, sampling a small subset of the atomic distribution is sufficient for the determination of the desired information. We take full high-resolution spectra of ultracold atoms by ionizing only 5% of the atoms. Using an additional microwave near 6.8 GHz, the detection scheme becomes energy, position and state selective. This can be used for in situ determination of the energy distribution and temperature of atom clouds inside the trap and applied for future correlation measurements.
We present an additive-manufactured microwave cavity for a Ramsey-type, double resonance, compact cold-atom clock. Atoms can be laser cooled inside the cavity using a grating magneto-optic trap with the cavity providing an excellent TE011-like mode while maintaining sufficient optical access for atomic detection. The cavity features a low Q-factor of 360 which conveniently reduces the cavity pulling of the future clock. Despite the potential porosity of the additive-manufacturing process, we demonstrate that the cavity is well-suited for vacuum. A preliminary clock setup using cold atoms allows for measuring the Zeeman spectrum and Rabi oscillations in the cavity which enables us to infer excellent field uniformity and homogeneity, respectively, across the volume accessed by the cold atoms. Ramsey spectroscopy is demonstrated, indicating that the cavity is suitable for clock applications. Finally, we discuss the limitations of the future clock.
Femtosecond coherent multidimensional spectroscopy is demonstrated for an ultracold gas. A setup for phase modulation spectroscopy is used to probe the 3 2 S 1/2 –2 2 P 1/2,3/2 transition in an 800 μ K-cold sample of 7 Li atoms confined in a magneto-optical trap. The observation of a double quantum coherence response, a signature of interparticle interactions, paves the way for detailed investigations of few- and many-body effects in ultracold gases using this technique. The experiment combines a frequency resolution of 3 GHz with a potential time resolution of 200 fs, which allows for high-resolution studies of ultracold atoms and molecules both in the frequency and in the time domain.