Stefan Alaric Schäffer
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View article: Modeling of a continuous superradiant laser on the sub-mHz <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:msup><mml:mrow/><mml:mn>1</mml:mn></mml:msup><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mn>0</mml:mn></mml:msub></mml:mrow><mml:mo>→</mml:mo><mml:mrow><mml:msup><mml:mrow/><mml:mn>3</mml:mn></mml:msup><mml:msub><mml:mi mathvariant="normal">P</mml:mi><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:mrow></mml:math> transition in neutral strontium-88
Modeling of a continuous superradiant laser on the sub-mHz transition in neutral strontium-88 Open
Continuous superradiance using a narrow optical transition has the potential to improve the short-term stability of state-of-the-art optical clocks. Even though pulsed superradiant emission on a mHz linewidth clock transition has been show…
View article: Continuous cavity QED with an atomic beam
Continuous cavity QED with an atomic beam Open
Atoms coupled to cavities provide an exciting playground for the study of fundamental interactions of atoms mediated through a common channel. Many of the applications of cavity QED and cold-atom experiments more broadly, suffer from limit…
View article: Codes for simulation of cooling, loading and pumping of Sr atoms.
Codes for simulation of cooling, loading and pumping of Sr atoms. Open
Collection of codes for simulation of cooling, loading and pumping Sr atoms in the optical conveyor. Basic details are presented in the file "code descr.pdf". For more details please refer to arXiv:2409.06575 .
View article: Continuous cavity-QED with an atomic beam
Continuous cavity-QED with an atomic beam Open
Atoms coupled to cavities provide an exciting playground for the study of fundamental interactions of atoms mediated through a common channel. Many of the applications of cavity-QED and cold-atom experiments more broadly, suffer from limit…
View article: Collectively enhanced Ramsey readout by cavity sub- to superradiant transition
Collectively enhanced Ramsey readout by cavity sub- to superradiant transition Open
When an inverted ensemble of atoms is tightly packed on the scale of its emission wavelength or when the atoms are collectively strongly coupled to a single cavity mode, their dipoles will align and decay rapidly via a superradiant burst. …
View article: Collectively enhanced Ramsey readout by cavity sub- to superradiant transition
Collectively enhanced Ramsey readout by cavity sub- to superradiant transition Open
When an inverted ensemble of atoms is tightly packed on the scale of its emission wavelength or when the atoms are collectively strongly coupled to a single cavity mode, their dipoles will align and decay rapidly via a superradiant burst. …
View article: Prospects of a superradiant laser based on a thermal or guided beam of Sr-88
Prospects of a superradiant laser based on a thermal or guided beam of Sr-88 Open
The prospects of superradiant lasing on the 7.5 kHz wide $^1$S$_0$-$^3$P$_1$ transition in $^{88}$Sr is explored by using numerical simulations of two systems based on realistic experimental numbers. One system uses the idea of demonstrati…
View article: Cavity-immune spectral features in the pulsed superradiant crossover regime
Cavity-immune spectral features in the pulsed superradiant crossover regime Open
Lasing in the bad cavity regime has promising applications in precision\nmetrology due to the reduced sensitivity to cavity noise. Here we investigate\nthe spectral properties and phase behavior of pulsed lasing on the $^1$S$_0 -\n^3$P$_1$…
View article: Optical atomic clock comparison through turbulent air
Optical atomic clock comparison through turbulent air Open
We use frequency comb-based optical two-way time-frequency transfer (O-TWTFT) to measure the optical frequency ratio of state-of-the-art ytterbium and strontium optical atomic clocks separated by a 1.5 km open-air link. Our free-space meas…
View article: Frequency Ratio Measurements with 18-digit Accuracy Using a Network of Optical Clocks
Frequency Ratio Measurements with 18-digit Accuracy Using a Network of Optical Clocks Open
Atomic clocks occupy a unique position in measurement science, exhibiting higher accuracy than any other measurement standard and underpinning six out of seven base units in the SI system. By exploiting higher resonance frequencies, optica…
View article: Lasing on a narrow transition in a cold thermal strontium ensemble
Lasing on a narrow transition in a cold thermal strontium ensemble Open
Highly stable laser sources based on narrow atomic transitions provide a\npromising platform for direct generation of stable and accurate optical\nfrequencies. Here we investigate a simple system operating in the\nhigh-temperature regime o…
View article: Towards the optical second: verifying optical clocks at the SI limit
Towards the optical second: verifying optical clocks at the SI limit Open
The pursuit of ever more precise measures of time and frequency motivates redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on the microwave hyperfine transition in…
View article: Optical-Clock-Based Time Scale.
Optical-Clock-Based Time Scale. Open
A time scale is a procedure for accurately and continuously marking the passage of time. It is exemplified by Coordinated Universal Time (UTC) and provides the backbone for critical navigation tools such as the Global Positioning System. P…
View article: Towards Adoption of an Optical Second: Verifying Optical Clocks at the SI Limit
Towards Adoption of an Optical Second: Verifying Optical Clocks at the SI Limit Open
The pursuit of ever more precise measures of time and frequency is likely to lead to the eventual redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on a microwave t…
View article: Faraday-Shielded dc Stark-Shift-Free Optical Lattice Clock
Faraday-Shielded dc Stark-Shift-Free Optical Lattice Clock Open
We demonstrate the absence of a dc Stark shift in an ytterbium optical lattice clock. Stray electric fields are suppressed through the introduction of an in-vacuum Faraday shield. Still, the effectiveness of the shielding must be experimen…
View article: Material-Dependencies of the THz emission from plasmonic graphene-based photoconductive antenna structures
Material-Dependencies of the THz emission from plasmonic graphene-based photoconductive antenna structures Open
Graphene supports surface plasmon polaritons with comparatively slow propagation velocities in the THz region, which becomes increasingly interesting for future communication technologies. This ability can be used to realize compact antenn…
View article: Dynamics of bad-cavity-enhanced interaction with cold Sr atoms for laser stabilization
Dynamics of bad-cavity-enhanced interaction with cold Sr atoms for laser stabilization Open
Hybrid systems of cold atoms and optical cavities are promising systems for increasing the stability of laser oscillators used in quantum metrology and atomic clocks. In this paper we map out the atom-cavity dynamics in such a system and d…
View article: Towards passive and active laser stabilization using cavity-enhanced atomic interaction
Towards passive and active laser stabilization using cavity-enhanced atomic interaction Open
Ultra stable frequency references such as the ones used in optical atomic clocks and for quantum metrology may be obtained by stabilizing a laser to an optical cavity that is stable over time. State-of-the-art frequency references are cons…