Active fiber-based retroreflector providing phase-retracing anti-parallel laser beams for precision spectroscopy

Area of Science:

• Atomic Physics
• Laser Spectroscopy
• Optical Engineering

Background:

• Precision spectroscopy requires minimizing Doppler shifts.
• Traditional methods using corner cubes have limitations in wavefront retracing and polarization preservation.
• Optical cavities are not always feasible for certain experimental setups.

Purpose of the Study:

• To introduce a novel active fiber-based retroreflector for high-quality phase-retracing laser beams.
• To demonstrate its application in precision spectroscopy of Doppler-sensitive transitions.
• To overcome limitations of existing retroreflector technologies.

Main Methods:

• An active fiber-based retroreflector was designed and implemented.
• The system generates anti-parallel Gaussian laser beams.
• Spectroscopy of the 2S-4P transition in atomic hydrogen was performed using the retroreflector.

Main Results:

• High-quality phase-retracing anti-parallel Gaussian laser beams were achieved.
• An average suppression of the first-order Doppler shift to 4 parts in 10^6 was demonstrated.
• The system enabled competitive uncertainty determinations of the Rydberg constant and proton charge radius.

Conclusions:

• The active fiber retroreflector offers superior performance over corner cubes for precision spectroscopy.
• It provides a viable alternative to high finesse cavities in challenging experimental environments.
• This technology facilitates advanced measurements of fundamental atomic properties.