Continuous-wave narrow-linewidth vacuum ultraviolet laser source

Area of Science:

• Nuclear Physics
• Quantum Optics
• Laser Spectroscopy

Background:

• The low-energy isomeric transition in Thorium-229 (229Th) is key for nuclear clock development.
• Previous research enabled initial spectroscopy but lacked suitable lasers for coherent control.
• An intense, narrow-linewidth vacuum ultraviolet (VUV) laser is crucial for manipulating the 229Th nucleus.

Purpose of the Study:

• To develop a continuous-wave (CW) laser source at 148.4 nm with an ultranarrow linewidth.
• To enable coherent nuclear manipulation for the 229Th nuclear clock.
• To establish a tunable VUV laser platform for quantum science and spectroscopy.

Main Methods:

• Generated a CW laser at 148.4 nm using four-wave mixing (FWM) in cadmium vapor.
• Achieved high power output (>100 nW) and broad wavelength tunability.
• Employed a spatially resolved homodyne technique to assess phase noise.

Main Results:

• Demonstrated a novel CW VUV laser source at 148.4 nm.
• Achieved a projected linewidth well below 100 Hz, a five-orders-of-magnitude improvement.
• Confirmed feasibility of sub-hertz VUV linewidths by constraining FWM-induced phase noise.

Conclusions:

• The developed laser addresses the primary challenge for a 229Th nuclear clock.
• This ultranarrow-linewidth VUV laser platform has broad potential applications.
• The technology opens new avenues in quantum information science, condensed-matter physics, and VUV spectroscopy.