Optical frequency combs are providing powerful tools for laser spectroscopy. Mode-locked femtosecond lasers and related emerging miniaturized devices can produce a large number of precisely evenly spaced spectral lines. Almost two decades ago, such spectral combs were introduced as tools for optical frequency metrology, motivated by the challenges of precision laser spectroscopy of atomic hydrogen as tests for fundamental physics laws. Current precision spectroscopy of hydrogen with frequency combs focuses on the "proton size puzzle", i.e. the discrepancy between the rms proton charge radius determined from Lamb shift measurements in ordinary hydrogen and in muonic hydrogen. Laser frequency combs provide the long-missing clockwork for optical atomic clocks, which are now approaching relative frequency uncertainties of 10-18. Distant clocks can be compared via optical fiber links at the 10-19 level, opening new opportunities for relativistic geodesy and astronomical interferometry. Frequency combs in space will permit new tests of Einstein's equivalence principle. As calibration tools for astronomical spectrographs, frequency combs are facilitating the search for exoplanets, and they may lead to direct evidence for the accelerating expansion of space in our universe. Laser combs are also enabling novel broadband molecular spectroscopy. They can dramatically improve the resolution and recording speed of Fourier spectrometers, and they are creating intriguing new opportunities for highly multiplexed nonlinear spectroscopy and microscopy.
Held Tuesdays at 4:30 pm in the William R. Hewlett Teaching Center, room 201.
Refreshments in the lobby of Varian Physics at 4:15 pm.
Spring 2015/2016, Committee: M. Schleier-Smith (Chair), G. Gratta, B. Lev, S. Zhang