Laser frequency combs have revolutionized the art of measuring the frequency of light. They have become the indispensible tools for precise laser spectroscopy from the THz region to the extreme ultraviolet. Their invention has been motivated by the long quest to study the spectrum of the simple hydrogen atom with the highest possible precision, in order to measure fundamental constants and to stringently test the fundamental laws of quantum physics.
Today, laser combs are serving as clockworks for optical atomic clocks, with applications from fundamental research to telecommunications and satellite navigation. By offering control of the electric field of extremely short light pulses, laser combs have become key tools for the emerging field of attosecond science. The calibration of astronomical spectrographs with laser combs will enable new searches for earth-like planets in distant solar systems, and may reveal the continuing expansion of space in the universe. Laser combs are revolutionizing molecular spectroscopy by dramatically extending the resolution and recording speed of Fourier spectrometers.
High harmonic generation promises to extend frequency comb techniques and precise spectroscopy into the extreme ultraviolet and soft X-ray regime.