A VUV frequency comb seems to be a promising candidate for performing high-resolution spectroscopy on the Th-229 nucleus. Such a device up-converts the frequency of a stabilized femtosecond laser from the infrared to the ultraviolet using a process called “high-harmonic generation” (HHG). This process is usually performed in noble gas jets. It requires extreme optical field amplitudes, which usually can only be realized when enhancing the laser power in a passive built-up cavity. The Vienna team has now demonstrated that such a process can be realized more efficiently using a solid-state target than a noble gas jet. The all-solid approach furthermore makes the setup simpler (no gas streaming into vacuum!) and compact. We could show that the solid-state HHG process maintains the original comb structure by performing a beating measurement with a UV CW laser at 266 nm, generously borrowed by the TOPTICA team. Further credits got to Erin Young and Jim Speck from University of California for producing the AlN targets. Read the full article HERE.