Spectroscopic atomic sample plane localization for precise digital holography.

Area of Science:

• Atomic physics
• Optical imaging
• Holography

Background:

• Digital holography enables volumetric reconstruction of scattered light fields.
• Simultaneous 3D inference of absorption and phase shifts is possible by refocusing.
• Standard refocusing methods fail for featureless cold atomic gases.

Purpose of the Study:

• To extend refocusing protocols for featureless atomic samples in digital holography.
• To develop a reliable method for identifying the sample plane of cold atomic gases.
• To enable precise 3D spectroscopic imaging of cold atomic samples.

Main Methods:

• Extended the Gouy phase anomaly refocusing protocol to free atomic samples.
• Utilized a spectral phase angle relation robust against probe variations.
• Employed numeric back-propagation with an "out-of-phase" response as the refocus criterion.

Main Results:

• Successfully determined the sample plane of laser-cooled ³⁹K gas.
• Achieved high axial resolution (δz ≈ 1 µm) with a holographic microscope (NA=0.3, λp=770 nm).
• Demonstrated reliable identification of atomic sample location despite featureless nature.

Conclusions:

• The extended Gouy phase anomaly method reliably locates cold atomic samples.
• This technique enhances 3D spectroscopic imaging capabilities for atomic gases.
• The findings are crucial for advanced atomic physics and quantum technologies.