Optical clock transitions are exceptionally accurate measurement tools, essential for various applications like precise timekeeping, testing fundamental physics constants, and performing quantum simulations of many-body physics. Addressing these transitions requires stable and well-controlled laser systems. This thesis presents the development of such a laser system, specially designed to address the strontium clock transition for quantum simulations. The work involves the design and construction of an optical setup for coupling an external-cavity diode laser of wavelength 698 nm into a Fabry-Pérot cavity and the application of the Pound-Drever Hall locking technique for frequency stabilization. The work also addresses the implementation of a vibrational isolation stage to mitigate external vibrations on the cavity and an isolation box for acoustic and thermal stability. By integrating advanced optical and electronic methods, the precision and stability of the clock laser are significantly improved.
Optical clock transitions are exceptionally accurate measurement tools, essential for various applications like precise timekeeping, testing fundamental physics constants, and performing quantum simulations of many-body physics. Addressing these transitions requires stable and well-controlled laser systems. This thesis presents the development of such a laser system, specially designed to address the strontium clock transition for quantum simulations. The work involves the design and construction of an optical setup for coupling an external-cavity diode laser of wavelength 698 nm into a Fabry-Pérot cavity and the application of the Pound-Drever Hall locking technique for frequency stabilization. The work also addresses the implementation of a vibrational isolation stage to mitigate external vibrations on the cavity and an isolation box for acoustic and thermal stability. By integrating advanced optical and electronic methods, the precision and stability of the clock laser are significantly improved.
Neutral atoms confined in optical dipole traps, commonly referred to as optical tweezers, have attracted significant attention in the fields of quantum simulation and computation. This is attributed to their notable flexibility, relatively long coherence times, and promising scalability when compared to more established physical systems, such as superconducting circuits and trapped ions. This thesis presents a proposal for a clock laser designed to target the 698 nm transition in the bosonic isotope of strontium,88Sr. An overview of the experimental setup, encompassing the apparatus configuration, the generation of optical tweezers, and the laser sequences employed, is provided in the introduction. Following this, the thesis examines mechanisms that facilitate the forbidden clock transition, specifically a two-photon scheme and the magnetic admixture scheme. Additionally, an analytical presentation of the anticipated systematic light shifts is provided, as well as the experimental parameters. The state detection scheme and the associated imaging scheme are presented. The isolation architecture implemented to meet the stringent requirements of the clock laser is described. Followed by a section presenting the design of the optical configuration, the generation of error signals, and the associated feedback loops. As part of this presentation, a concise review of the Pound-Drever-Hall (PDH), fiber noise cancellation (FNC) and optical beating techniques is provided. Finally, the thesis outlines the preliminary scheme of generating Rydberg excitations and it manipulations following the implementation of the clock laser. Furthermore, the thesis notes several ongoing projects, such as the assembly and calibration of an improved spectroscopy cell and an external cavity diode laser (ECDL). Additionally, a concept for incorporating machine learning techniques to improve experimental efficiency is presented prior to the conclusion.
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.
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.
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.
Clocks based on optical transitions in ions and atoms are quickly moving to the forefront of the frequency standards field mainly because of the high spec-tral resolution, and therefore the potential stability and accuracy, which can be achieved. In this thesis a new optical clock based on neutral atoms trapped in an optical lattice is presented, demonstrating spectroscopy of the clock transition free of any lineshape or accuracy degradation due to atomic motion. The system simu-lates a single trapped ion clock, but allows use of thousands of atoms for improved signal to noise ratio, and clock stability. High accuracy can also be achieved as the lattice can be designed to shift the energy of the two atomic clock states equally, such that the transition frequency is unchanged. Strontium is a natural candidate for such a clock as it offers an extremely narrow optical transition (∼1 mHz) based on atomic states which are very insensitive to external fields. The strontium level structure allows efficient laser cooling to 1 µK with diode laser sources, and a con-venient wavelength of 813 nm for the zero-differential Stark shift optical lattice. The strontium lattice clock system has allowed observation of high signal-to-noise
We are studying a single Sr/sup +/ atom confined in a Paul trap to produce a frequency standard in the visible region of the spectrum. The goal is to excite a clock transition of the ion at 674 nm with a diode laser and measure its absolute frequency. It is only possible to probe the 0.3-Hz transition if the diode laser is extremely stable during the measurement process which in this experiment can take several minutes to complete. Frequency stabilization of the probing laser was achieved with a lock to an ultra-stable Fabry-Perot cavity. The cavity was temperature stabilized and has demonstrated good long term stability.