The characterisation of deep-ultraviolet ultrafast pulses by active synchronisation via balanced cross-correlation

This thesis details techniques necessary for the characterisation of the deep UV output from mode-locked cerium lasers. Previously 6 ps pulses have been obtained from an 80 MHz Ce:LiCAF laser, but these pulses are likely to have been chirped given there was no intracavity dispersion control. Full characterisation, using techniques such as frequency resolved optical gating (FROG), is needed to further develop these novel solid-state ultraviolet laser systems to their full potential as femtosecond or even attosecond lasers. The most appropriate technique for characterisation of deep UV ultrafast pulses is to perform synchronous cross correlation FROG (X-FROG) measurements using an auxilliary femtosecond Ti:sapphire laser as a reference. The first steps to achieving this are to synchronise two independent ultrafast lasers: the Ce:LiCAF laser under test with a femtosecond Ti:sapphire laser. Given that the Ce:LiCAF laser is itself synchronously pumped by the 266 nm fourth harmonic from a mode-locked Nd:YVO4 laser, initial synchronisation of the Ti:sapphire laser to the Nd:YVO4 laser is suitable for evaluating synchronisation and UV X-FROGtechniques. A femtosecond Ti:sapphire laser was synchronised to an independently running mod elocked Nd:YVO4 laser using balanced synchronisation techniques, and the timing uncertainties of the synchronisation were evaluated. Synchronous and asynchronous cross-correlation and FROG techniques were employed to evaluate the 266 nm pump laser and Ti:sapphire reference laser ultrafast pulses. This is the key first step to performing such measurements on the output of a cerium laser to allow further optimisation and external pulse compression of this system.