Precision laser spectroscopy of rubidium with a Frequency Comb

The development of the optical frequency comb technique has transformed the field of spectroscopy, allowing the measurement of atomic transition frequencies to unprecedented levels of accuracy. In this thesis a frequency comb has been used to make absolute frequency measurements of optical transitions to highly excited Rydberg levels in Rb. The reliable measurement of these levels plays an important role in improving the accuracy of atomic models and the widely used Rb atom is an excellent candidate for such studies. A laser system has been constructed and optimised for resolving these highly excited states in an ordinary vapour cell, using a Doppler-free technique of purely optical detection. After several developments to the apparatus, the absolute energies of a collection of Rydberg levels have been measured to an accuracy of 3 parts in 1010, demonstrating the first sub-megahertz accuracy optical Rydberg spectroscopy. A vapour cell is a convenient and straightforward solution for finding Rydberg levels and these findings show that cell-based detection techniques could potentially permit rapid advances in the field. Along the way, the vapour cell sample has also highlighted many interesting areas of exploration: For example, it has allowed long term laser stabilisation to Rydberg levels for experiments such as the micromaser. Also, the Rydberg atoms in the cell have been manipulated by microwaves, allowing the study of high ` = 4 states, which has illuminated a whole range of new experiments. It has even been found that one of the limiting factors of these cell-based schemes may be the knowledge of the frequency of lower lying transitions, which has ultimately led this research into a secondary area, involving the measurement of the Rb D lines with a frequency comb. Together, these findings have exposed a large variety of atomic physics to be investigated in the future.