Interrogating the Temporal Coherence of EUV Frequency Combs with Highly Charged Ions

Area of Science:

• Atomic Physics
• Quantum Optics
• Ultrafast Lasers

Background:

• Extreme ultraviolet (EUV) frequency combs are crucial for advanced spectroscopy.
• Intracavity high-order harmonic generation (HHG) is a primary source for EUV frequency combs.
• Verifying the temporal coherence of EUV combs is essential for their applications.

Purpose of the Study:

• To propose a novel scheme for inferring the temporal coherence of EUV frequency combs.
• To demonstrate a method for verifying coherence over timescales significantly longer than current capabilities.
• To enable high-precision spectroscopy of EUV transitions.

Main Methods:

• Simulating the excitation dynamics of highly charged Mg-like ions interacting with EUV pulse trains.
• Analyzing the spectral properties of ion excitations to determine coherence time.
• Investigating the microscopic origins of macroscopic equivalence between pulsed and continuous-wave laser excitations.

Main Results:

• A direct correlation between the spectrum of ion excitations and the coherence time of the EUV pulse train was established.
• The microscopic equivalence between pulsed and continuous-wave laser excitations was demonstrated.
• The proposed scheme allows for coherence time determination at timescales several orders of magnitude longer than current methods.

Conclusions:

• The developed scheme offers a robust method for verifying the temporal coherence of EUV frequency combs.
• This advancement enables ultra-high-precision spectroscopy of EUV transitions with relative accuracy up to 10^-17.
• The findings pave the way for new applications in attosecond science and precision measurements.