Phase-stabilized UV light at 267 nm through twofold second harmonic generation

Area of Science:

• Atomic, Molecular, and Optical Physics
• Laser Physics and Photonics
• Quantum Metrology

Background:

• Phase-stable laser light is crucial for enhancing the interrogation time of optical clocks.
• Achieving longer interrogation times directly translates to reduced statistical uncertainties in optical clock measurements.
• The 27Al+ ion optical clock requires highly stable laser light for precise measurements.

Purpose of the Study:

• To report a novel laser system for generating phase-stabilized ultraviolet (UV) light.
• To provide a laser source suitable for high-precision optical clocks, specifically the aluminum ion optical clock.
• To demonstrate the feasibility of extending optical clock interrogation times through advanced laser stabilization techniques.

Main Methods:

• Frequency quadrupling of a 1069.6 nm fiber laser using two cascaded nonlinear crystals (PPLN waveguide and DKDP).
• Single-pass configuration for both nonlinear crystals to generate UV light at 267.4 nm.
• Beat-node measurement utilizing an existing phase-stabilized quadrupling system to assess short-term phase stability.

Main Results:

• Generation of over 50 µW of phase-stabilized UV light at 267.4 nm.
• Achieved a fractional frequency instability of less than 5x10^-17 at 1 second, supporting lifetime-limited probing.
• Demonstrated an electronically limited instability of 1x10^-18 at 1 second with in-loop error signal.

Conclusions:

• The developed laser system successfully provides phase-stabilized UV light for optical clocks.
• The achieved stability is sufficient for lifetime-limited probing of the 27Al+ clock transition.
• Further improvements in stability are anticipated through interferometric path length stabilization.