UC Berkeley

The development of attosecond technology is one of the most significant recent achievements in the field of ultrafast optics; it opens up new frontiers in atomic and molecular spectroscopy and dynamics. A unique attosecond pumpprobe apparatus using a compact Mach-Zehnder interferometer is developed. The interferometer system is compact (∼290 cm²) and completely located outside of the vacuum chamber. The location reduces the mechanical vibration from vacuum components such as turbopumps and roughing pumps. The stability of the interferometer is ∼50 as RMS over 24 hours, stabilized with an active feedback loop. The pump and probe fields can be easily altered to incorporate multiple colors. In the interferometer, double optical gating optics are arranged to generate isolated attosecond pulses with a supercontinuum spectrum. The frequencies of the attosecond pulses can be selected to be in the extreme ultraviolet (XUV) region (25–55 eV, 140 as) or the vacuum ultraviolet (VUV) region (15–24 eV, ∼400 as) by metal filters. Furthermore, the near infrared probe field (1.65 eV) can be upconverted to the ultraviolet (3.1 eV). The frequency tunability in the XUV and VUV is critical for selecting excited states of target atoms and molecules.