Narrow linewidth lasers for use with neutral strontium as a frequency standard

摘要

The continual development of precise timing has always pushed technology forward, and the latest generation of clocks uses electronic transitions within cooled atoms as their frequency reference. For atoms where the clock transition is at an optical frequency an ultra stable laser is used to probe the transition; the construction and development of this laser for use with strontium is the subject of this thesis. The system consists of a laser, an optical cavity and the electronics to lock the laser to the optical cavity. The theoretical component of this thesis looked into the possible materials used to make the optical cavity from and how the optical cavity should be supported to minimize the frequency noise of the laser. A compact external cavity diode laser was constructed and shown to have a linewidth of 26 ±15 kHz. To lock and narrow the linewidth of this laser, two ultra stable optical cavity assemblies were constructed with vibration and thermal stabilisation enclosures. To characterise the laser stability a beat measurement was performed between the two stabilised lasers and a beat note linewidth of 1:37 ± 0:28 Hz was measured. The instability of the beat note was measured; an Allan deviation of 2 x10(^-)(^1)(^4) was obtained between averaging times of 0.2 s and 1 s.