Advanced laser frequency stabilisation systems for mobile strontium optical lattice clocks

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). A 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