XUV frequency comb operation in an astigmatism-compensated enhancement cavity

Abstract

We have developed an extreme ultraviolet (XUV) frequency comb for performing ultra-high precision spectroscopy on the many XUV transitions found in highly charged ions (HCI). Femtosecond pulses from a 100 MHz phase-stabilized near-infrared frequency comb are amplified and then fed into a femtosecond enhancement cavity (fsEC) inside an ultra-high vacuum chamber. The low-dispersion fsEC coherently superposes several hundred incident pulses and, with a single cylindrical optical element, fully compensates astigmatism at the $w_0=15\mu$m waist cavity focus. With a gas jet installed there, intensities reaching $\sim 10^{14}$ W/cm${}^2$ generate coherent high harmonics with a comb spectrum at 100 MHz rate. We couple out of the fsEC harmonics from the 7th up to the 35th (42 eV; 30 nm) to be used in upcoming experiments on HCI frequency metrology.

12 pages, 6 figures

References in corpus (12)

• Frequency comb spectroscopy
• Optical frequency comb technology for ultra-broadband radio-frequency photonics
• Direct detection of the 229Th nuclear clock transition
• Enhanced effect of temporal variation of the fine structure constant in diatomic molecules
• Enhanced laboratory sensitivity to variation of the fine-structure constant using highly-charged ions
• Coherent laser spectroscopy of highly charged ions using quantum logic
• Lifetime measurement of the ${}^{229}$Th nuclear isomer
• Efficient output coupling of intracavity high harmonic generation
• Highly charged ions with E1, M1, and E2 transitions within laser range
• Optical transitions in highly-charged californium ions with high sensitivity to variation of the fine-structure constant
• High-Precision Ramsey-Comb Spectroscopy Based on High-Harmonic Generation
• Interrogating the temporal coherence of EUV frequency combs with highly charged ions