With its direct correspondence to the electronic structure, angle-resolved photoemission spectroscopy (ARPES) is a ubiquitous tool for the study of solids. When extended to the temporal domain, time-resolved (TR)-ARPES offers the potential to move beyond equilibrium properties, exploring both the unoccupied electronic structure as well as its dynamical response under ultrafast perturbation. By performing high-harmonic generation inside a femtosecond enhancement cavity (fsEC), we realized a practical source for TR-ARPES that achieves a flux of over 10^11 photons/s delivered to the sample, and operates over a range of 8-40 eV with a repetition rate of 60 MHz. This source enables TR-ARPES studies with a temporal and energy resolution of 190 fs and 22 meV, respectively. To showcase the capabilities of this setup, we develop a novel approach to determine the mode-projected electron-phonon matrix element in graphite, with unprecedented sensitivity, directly in the time domain.
Recent development of extreme ultraviolet (XUV) sources based on high harmonic generation (HHG) in femtosecond enhancement cavities (fsEC) has enabled generation of high photon ux ( ̴ 1013-1014 photons/sec) in the XUV, at high repetition rates (> 50 MHz) and spanning the spectral region from 40 nm - 120 nm. Here we demonstrate the potential offered by this approach for angle-resolved photoemission spectroscopy by measuring the photoemission spectrum of Au using 8.3 and 25 eV photons with excellent resolution at rapid data rates.
We report on the development of a compact multiphoton microscopy (MPM) system based on a frequency-doubled, femtosecond erbium-doped fiber laser source at 1.58 μm. By use of periodically poled MgO:LiNbO3, frequency-doubled pulses at 790 nm with average power of 75 mW and pulse width of 130 fs are applied as the excitation source. The fiber laser is optimized for its parameters along with the dispersive properties of the delivery fiber such that the MPM signal is maximized at the sample location. Micro-electro-mechanical system (MEMS) scanner, miniature objective, and multimode fiber are further used to make the MPM system compact. MPM images are obtained from unstained biological samples. The MPM system with a compact, portable, low-cost fiber laser has a great potential to transform the bench-top MPM system to a portable system for in vivo MPM imaging.
Conference Committee Involvement (1)
Time and Frequency Metrology
29 August 2007 | San Diego, California, United States