Below-threshold harmonic generation in gas-jets for Th-229 nuclear spectroscopy

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Laser Physics

Background:

• Below-threshold harmonic generation in gas jets is a key method for producing vacuum ultra-violet (VUV) light.
• VUV light sources are essential for applications like probing nuclear isomeric transitions, such as that of Thorium-229.
• Developing efficient VUV frequency combs requires understanding harmonic generation efficiencies.

Purpose of the Study:

• To measure the conversion efficiencies of below-threshold harmonics generated in Argon and Krypton gas jets.
• To assess the potential of Ytterbium-based laser sources for generating VUV frequency combs.
• To provide crucial data for the development of practical VUV light sources.

Main Methods:

• Utilized a phase-mismatched generation scheme with Argon and Krypton as nonlinear media.
• Employed a 220 fs, 1030 nm Ytterbium laser source to generate 7th and 5th harmonics.
• Characterized the 3rd harmonic generation from a 178 fs, 515 nm laser source.

Main Results:

• Achieved a maximum conversion efficiency of 1.1 × 10⁻⁵ for the 7th harmonic (147 nm) using the 1030 nm source.
• Obtained a maximum conversion efficiency of 0.78 × 10⁻⁴ for the 5th harmonic (206 nm).
• Measured a maximum conversion efficiency of 0.3% for the 3rd harmonic (172 nm) from the 515 nm source.

Conclusions:

• Below-threshold harmonic generation in gas jets is a viable route to VUV frequency combs.
• The measured efficiencies are critical for designing and optimizing VUV sources for spectroscopic applications.
• This work advances the development of VUV light sources for fundamental science and potential applications.