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

Magneto-optical trapping of strontium for use as a mobile frequency reference

Bjorn Ole Kock

Published Dec 1, 2013• 6 citations
OpenAlex

Abstract

Atomic Caesium clocks have made an astonishing development in the past few decades, with them gaining an order of magnitude in precision every decade. A new generation of atomic optical clocks is now emerging, which is moving to the forefront of timekeeping. By going from microwave to optical frequencies these clocks are now reaching fractional uncertainty levels in the 10\\(^-\\)\\(^1\\)\\(^8\\), opening a whole new range of exciting applications. This thesis presents the design and implementation of an experiment for laser cooling of strontium atoms, focusing on the mobility of the setup, opening a range of new applications as a mobile clock. The experimental apparatus applies a range of new techniques for strontium, such as the use of a two dimensional magneto-optical trap for pre cooling atoms, allowing for a compact and transportable system. A mobile laser system for laser cooling strontium atoms was realized. This includes a frequency doubling system for the main cooling transition. The constructed monolithic frequency doubling cavity has generated 300 mW of blue light and proven to be a stable setup suitable for a mobile system. The 3D-MOT was able to capture 4 * 10\\(^5\\) atoms with a long lifetime of 5.5 s, with further improvements for a significant increase in atom number currently being implemented.

Related papers

Towards a strontium based stationary optical lattice clock

Qasim Hassan Ubaid

Optical atomic clocks have proven to be the most stable clocks with the lowest systematic uncertainty which has now reached a record level of (9.4 X10/(^{19}/)). Thus optical clocks now surpass the best fountain Cs atomic clocks by three orders of magnitude which opens the prospect of using optical clocks as frequency standards for timekeeping in the near future. \n \nThis thesis describes the progress that has been made towards a stationary optical lattice clock based on strontium atoms, and reports the results of an ongoing characterization. \n \nAn experimental apparatus was designed and built to efficiently slow, cool, and trap the strontium atoms which represent the heart of the strontium optical lattice clock discussed in this thesis. The novel aspects of the experimental development described in the thesis comprise a frequency doubling cavity for producing 461 nm laser light employed for cooling and trapping the strontium atoms in the first stage cooling. This cavity provided sufficient power for cooling and trapping the strontium atoms for up to 300 mW of 461 nm laser light. Furthermore, a new design of Zeeman slower based on spherical permanent magnets was produced, built and characterized. \n \nThe slower is compact, tunable, easy to assemble and maintain, and cost-effective as the permanent magnets do not require any power supply or water cooling. It is suggested that this kind of Zeeman slower constitutes an ideal solution for portable optical clock systems. A blue magneto-optical trap was realized for the first time with such a Zeeman slower. With about 30 mW of a 461 nm laser, up to 6X10/(^8/) atoms were captured.

•Jul 20, 2020•0 citations

Towards miniaturized strontium optical lattice clock

Wei He

Optical atomic clocks with precisions and accuracies in the 10\(^-\)\(^1\)\(^8\) level [1] are now the most advanced man-made timekeeping devices. They outperform the microwave cesium atomic clocks that realize the SI definition of the second. Scaling down the size of optical atomic clocks may open the door to a range of industrial and space applications. In this thesis, the design and preliminary results of a compact strontium cooling system are presented. In the first cooling stage, the high power 461 nm laser with 300 mW output features a modular design, while smaller laser sources for demonstrating a strontium magneto-optical trap have also been investigated. An innovative design that couples a spectroscopy cell directly into the scientific chamber reduces the overall size and power consumption of the system. Additionally, using strontium oxide as a source of strontium atoms suitable for optical clocks has achieved initial success. For the first time, a single-beam MOT configuration is applied to strontium. In this novel apparatus, the blue MOT and red MOT broadband cooling phases are able to trap 5x10\(^6\) and 1000 atoms, respectively. This work shows promising progress towards developing a functional miniaturized strontium optical lattice clock.

•Jul 1, 2017•5 citations

Development of an Apparatus for a Strontium Optical Lattice Optical Frequency Standard

Ian R. Hill

Accurate time keeping is critical to the function and advancement of many human endeavours. Atomic clocks based on a microwave transition in atomic Cs have served as primary frequency standards to realise the SI second since their formal adoption in 1967. State-of-the-art, laser cooled, Cs fountains now routinely operate with fractional frequency uncertainties below the 10⁻¹⁵ level in laboratories throughout the world. Over the last decade, efforts to build frequency standards based on optical transitions have come to fruition and potential inaccuracies below the 10⁻¹⁷ level have been demonstrated. Such standards point to the future of time keeping and much development is being pursued to realise the potential of these 'next generation' optical clocks. One such approach, on which this work focusses, relies on a 'magic' wavelength optical lattice trap to provide (almost) Doppler- and recoil-free confinement of atoms during clock interrogation. At this 'magic' wavelength, light induced perturbation of the clock states is equal and so cancels precisely. This thesis describes the design and implementation of an optical lattice frequency standard apparatus based on 88Sr held in a 1D optical lattice. A review of the development of atomic frequency metrology is given from a historical viewpoint and the technology and limitations of current methods discussed. To tackle the blackbody radiation shift, which currently presents the greatest limitation to the Sr lattice clock, imposing at the 10⁻¹⁶ level, a scheme to measure the blackbody radiation shift coefficient at the 10⁻¹⁷ level is developed. Techniques to laser cool and trap atomic strontium are described and the implementation detailed. All laser systems required for clock operation are described including the design and implementation of extended-cavity diode lasers for precision spectroscopy. Details relevant to the eventual operation of the apparatus are discussed.

•Jun 1, 2012•3 citations

Laser controlled atom source for optical clocks

Ole Kock, Wei Jian He, Dariusz Świerad +4 more

Precision timekeeping has been a driving force in innovation, from defining agricultural seasons to atomic clocks enabling satellite navigation, broadband communication and high-speed trading. We are on the verge of a revolution in atomic timekeeping, where optical clocks promise an over thousand-fold improvement in stability and accuracy. However, complex setups and sensitivity to thermal radiation pose limitations to progress. Here we report on an atom source for a strontium optical lattice clock which circumvents these limitations. We demonstrate fast (sub 100 ms), cold and controlled emission of strontium atomic vapours from bulk strontium oxide irradiated by a simple low power diode laser. Our results demonstrate that millions of strontium atoms from the vapour can be captured in a magneto-optical trap (MOT). Our method enables over an order of magnitude reduction in scale of the apparatus. Future applications range from satellite clocks testing general relativity to portable clocks for inertial navigation systems and relativistic geodesy.

Scientific Reports•Nov 18, 2016•34 citations

Miniaturized setups for magneto-optical trapping of ytterbium and strontium

Julian Pick, Julia Voß, Florian Löwinger +6 more

Optical lattice clocks based on ytterbium (Yb) and strontium (Sr) are emerging as key technologies in precision timekeeping and metrology. Recent advancements in miniaturization and transportability are making them increasingly accessible for applications outside traditional laboratory settings. However, the degree of miniaturization is limited by the atomic source that is used to provide laser-cooled atoms for the clock spectroscopy. Conventional atomic sources for optical lattice clocks consist of a high-power oven and a magneto-optical trap (MOT) that requires six incident laser beams for three-dimensional trapping and cooling. Here, we present technologies that allow a significant miniaturization of the required experimental setups to realize a MOT for Yb and Sr. These are a chip-based microstructured atomic oven and in-vacuum optical elements that require only a single incident laser beam to generate all of the required beams for three-dimensional trapping and cooling. The oven was manufactured with LIDE® (laser induced deep etching). It was paired with an aluminum pyramid reflector to load Yb atoms into a MOT. The oven was placed directly at the outside of the reflector, forming a compact setup that is used for atom evaporation and direct trapping and cooling. In this configuration, MOT loading rates above 10^8 atoms/s were measured for oven heating powers below 250 mW. Furthermore, the microstructured oven was paired with a grating MOT chip inside a highly compact vacuum chamber. The chamber was additively manufactured from titanium and the assembled setup spans a volume of less than 750 ml. In this setup, up to 10^5 Sr atoms were trapped in the MOT.

•Jan 1, 2026•0 citations

Advanced laser frequency stabilisation systems for mobile strontium optical lattice clocks

S. Viswam

Strontium optical lattice clocks have undergone vast developments in the past decade with world leading frequency stability and uncertainty records. Now, a lot of scientists are moving from laboratory based clocks to transportable, and portable clocks for applications including space, fundamental science, finance, and communication. The research team at the University of Birmingham are working towards developing transportable apparatus for studying fundamental physics, global positioning system (GPS), and geodesy applications. This thesis reports on the progress towards two different transportable strontium optical lattice clocks, which we will call ‘miniclock’ and ‘Space Optical lattice Clock 2’ (SOC2). \nA diode-seeded tapered amplifier based narrow linewidth laser is developed and used to realise second stage cooling of strontium in miniclock apparatus. The laser has achieved a linewidth of 1 kHz after stabilising to a 3 cm long optical reference cavity. A multiple frequency stabilisation unit (FSU) for strontium lattice clocks is established. It is a robust, portable, and compact frequency stabilisation unit with a volume of 593 cm^3. Three different lasers are currently locked simultaneously to the FSU cavity, which could be extended to any number of lasers, enabling to use a single cavity for locking all the lasers required in a strontium lattice clock, except the clock laser. FSU is designed specifically for use in compact clocks. In the SOC2 system, realisation of clock transition and its characterisation are performed. A transition linewidth of 3 Hz is obtained for the SOC2 strontium clock. Further details and results are described in the thesis.

•Jul 13, 2020•2 citations
Atomic Caesium clocks have made an astonishing development in the past few decades, with them gaining an order of magnitude in precision every decade. A new generation of atomic optical clocks is now emerging, which is moving to the forefront of timekeeping. By going from microwave to optical frequencies these clocks are now reaching fractional uncertainty levels in the 10\(^-\)\(^1\)\(^8\), opening a whole new range of exciting applications. This thesis presents the design and implementation of an experiment for laser cooling of strontium atoms, focusing on the mobility of the setup, opening a range of new applications as a mobile clock. The experimental apparatus applies a range of new techniques for strontium, such as the use of a two dimensional magneto-optical trap for pre cooling atoms, allowing for a compact and transportable system. A mobile laser system for laser cooling strontium atoms was realized. This includes a frequency doubling system for the main cooling transition. The constructed monolithic frequency doubling cavity has generated 300 mW of blue light and proven to be a stable setup suitable for a mobile system. The 3D-MOT was able to capture 4 * 10\(^5\) atoms with a long lifetime of 5.5 s, with further improvements for a significant increase in atom number currently being implemented.
Optical atomic clocks have proven to be the most stable clocks with the lowest systematic uncertainty which has now reached a record level of (9.4 X10/(^{19}/)). Thus optical clocks now surpass the best fountain Cs atomic clocks by three orders of magnitude which opens the prospect of using optical clocks as frequency standards for timekeeping in the near future. \n \nThis thesis describes the progress that has been made towards a stationary optical lattice clock based on strontium atoms, and reports the results of an ongoing characterization. \n \nAn experimental apparatus was designed and built to efficiently slow, cool, and trap the strontium atoms which represent the heart of the strontium optical lattice clock discussed in this thesis. The novel aspects of the experimental development described in the thesis comprise a frequency doubling cavity for producing 461 nm laser light employed for cooling and trapping the strontium atoms in the first stage cooling. This cavity provided sufficient power for cooling and trapping the strontium atoms for up to 300 mW of 461 nm laser light. Furthermore, a new design of Zeeman slower based on spherical permanent magnets was produced, built and characterized. \n \nThe slower is compact, tunable, easy to assemble and maintain, and cost-effective as the permanent magnets do not require any power supply or water cooling. It is suggested that this kind of Zeeman slower constitutes an ideal solution for portable optical clock systems. A blue magneto-optical trap was realized for the first time with such a Zeeman slower. With about 30 mW of a 461 nm laser, up to 6X10/(^8/) atoms were captured.
Optical atomic clocks with precisions and accuracies in the 10−^-−1^118^88 level [1] are now the most advanced man-made timekeeping devices. They outperform the microwave cesium atomic clocks that realize the SI definition of the second. Scaling down the size of optical atomic clocks may open the door to a range of industrial and space applications. In this thesis, the design and preliminary results of a compact strontium cooling system are presented. In the first cooling stage, the high power 461 nm laser with 300 mW output features a modular design, while smaller laser sources for demonstrating a strontium magneto-optical trap have also been investigated. An innovative design that couples a spectroscopy cell directly into the scientific chamber reduces the overall size and power consumption of the system. Additionally, using strontium oxide as a source of strontium atoms suitable for optical clocks has achieved initial success. For the first time, a single-beam MOT configuration is applied to strontium. In this novel apparatus, the blue MOT and red MOT broadband cooling phases are able to trap 5x106^66 and 1000 atoms, respectively. This work shows promising progress towards developing a functional miniaturized strontium optical lattice clock.
Accurate time keeping is critical to the function and advancement of many human endeavours. Atomic clocks based on a microwave transition in atomic Cs have served as primary frequency standards to realise the SI second since their formal adoption in 1967. State-of-the-art, laser cooled, Cs fountains now routinely operate with fractional frequency uncertainties below the 10⁻¹⁵ level in laboratories throughout the world. Over the last decade, efforts to build frequency standards based on optical transitions have come to fruition and potential inaccuracies below the 10⁻¹⁷ level have been demonstrated. Such standards point to the future of time keeping and much development is being pursued to realise the potential of these 'next generation' optical clocks. One such approach, on which this work focusses, relies on a 'magic' wavelength optical lattice trap to provide (almost) Doppler- and recoil-free confinement of atoms during clock interrogation. At this 'magic' wavelength, light induced perturbation of the clock states is equal and so cancels precisely. This thesis describes the design and implementation of an optical lattice frequency standard apparatus based on 88Sr held in a 1D optical lattice. A review of the development of atomic frequency metrology is given from a historical viewpoint and the technology and limitations of current methods discussed. To tackle the blackbody radiation shift, which currently presents the greatest limitation to the Sr lattice clock, imposing at the 10⁻¹⁶ level, a scheme to measure the blackbody radiation shift coefficient at the 10⁻¹⁷ level is developed. Techniques to laser cool and trap atomic strontium are described and the implementation detailed. All laser systems required for clock operation are described including the design and implementation of extended-cavity diode lasers for precision spectroscopy. Details relevant to the eventual operation of the apparatus are discussed.
Precision timekeeping has been a driving force in innovation, from defining agricultural seasons to atomic clocks enabling satellite navigation, broadband communication and high-speed trading. We are on the verge of a revolution in atomic timekeeping, where optical clocks promise an over thousand-fold improvement in stability and accuracy. However, complex setups and sensitivity to thermal radiation pose limitations to progress. Here we report on an atom source for a strontium optical lattice clock which circumvents these limitations. We demonstrate fast (sub 100 ms), cold and controlled emission of strontium atomic vapours from bulk strontium oxide irradiated by a simple low power diode laser. Our results demonstrate that millions of strontium atoms from the vapour can be captured in a magneto-optical trap (MOT). Our method enables over an order of magnitude reduction in scale of the apparatus. Future applications range from satellite clocks testing general relativity to portable clocks for inertial navigation systems and relativistic geodesy.
Optical lattice clocks based on ytterbium (Yb) and strontium (Sr) are emerging as key technologies in precision timekeeping and metrology. Recent advancements in miniaturization and transportability are making them increasingly accessible for applications outside traditional laboratory settings. However, the degree of miniaturization is limited by the atomic source that is used to provide laser-cooled atoms for the clock spectroscopy. Conventional atomic sources for optical lattice clocks consist of a high-power oven and a magneto-optical trap (MOT) that requires six incident laser beams for three-dimensional trapping and cooling. Here, we present technologies that allow a significant miniaturization of the required experimental setups to realize a MOT for Yb and Sr. These are a chip-based microstructured atomic oven and in-vacuum optical elements that require only a single incident laser beam to generate all of the required beams for three-dimensional trapping and cooling. The oven was manufactured with LIDE® (laser induced deep etching). It was paired with an aluminum pyramid reflector to load Yb atoms into a MOT. The oven was placed directly at the outside of the reflector, forming a compact setup that is used for atom evaporation and direct trapping and cooling. In this configuration, MOT loading rates above 10^8 atoms/s were measured for oven heating powers below 250 mW. Furthermore, the microstructured oven was paired with a grating MOT chip inside a highly compact vacuum chamber. The chamber was additively manufactured from titanium and the assembled setup spans a volume of less than 750 ml. In this setup, up to 10^5 Sr atoms were trapped in the MOT.
Strontium optical lattice clocks have undergone vast developments in the past decade with world leading frequency stability and uncertainty records. Now, a lot of scientists are moving from laboratory based clocks to transportable, and portable clocks for applications including space, fundamental science, finance, and communication. The research team at the University of Birmingham are working towards developing transportable apparatus for studying fundamental physics, global positioning system (GPS), and geodesy applications. This thesis reports on the progress towards two different transportable strontium optical lattice clocks, which we will call ‘miniclock’ and ‘Space Optical lattice Clock 2’ (SOC2). \nA diode-seeded tapered amplifier based narrow linewidth laser is developed and used to realise second stage cooling of strontium in miniclock apparatus. The laser has achieved a linewidth of 1 kHz after stabilising to a 3 cm long optical reference cavity. A multiple frequency stabilisation unit (FSU) for strontium lattice clocks is established. It is a robust, portable, and compact frequency stabilisation unit with a volume of 593 cm^3. Three different lasers are currently locked simultaneously to the FSU cavity, which could be extended to any number of lasers, enabling to use a single cavity for locking all the lasers required in a strontium lattice clock, except the clock laser. FSU is designed specifically for use in compact clocks. In the SOC2 system, realisation of clock transition and its characterisation are performed. A transition linewidth of 3 Hz is obtained for the SOC2 strontium clock. Further details and results are described in the thesis.