Advanced Lasers for High Resolution Spectroscopy

Laser spectroscopy is a driving force in fundamental research projects in various fields. The advances in laser technology is fueling scientific findings. In many spectroscopy experiments, external cavity diode lasers (ECDL) interrogate a prepared sample, e.g. molecular gases, atoms or even rare isotopes. Frequency doubling and quadrupling allows for reliable tunable cw laser radiation down to 190 nm. The high performance and reliability of our ECDLs are oftentimes essential to reach new scientific findings. In order to put such cw-lasers to work, i.e. to integrate them into high-resolution spectroscopy experiments, it is often required to measure the frequency of the laser field. Frequency combs based on femtosecond lasers enable absolute frequency measurements. Our commercial frequency comb uses difference frequency generation (DFG), which is advantageous for stability and robustness. In this talk, I will highlight the impact of high performance laser systems by discussing selected experiments. Ultra-stable lasers: Linewidths below 1 Hz, i.e. below 10-15 instability o Reducing the linewidth of a free running ECDLs o Locking lasers to ultra-high finesse optical cavities o Potential of further improvements - High Power visible and UV lasers - Frequency combs o CEO (carrier envelope offset frequency) free by DFG (difference frequency generation) o 1 Hz comb teeth across spectrum - Optical clocks o State of the art o Impact on fundamental research and geodesy o Why going to space? o Relevance of latest developments for SI discussions