Quantitative detection of substances without feature absorption peak by terahertz Rydberg atom sensor

Area of Science:

• Physics
• Spectroscopy
• Material Science

Background:

• Quantitative terahertz (THz) testing is advancing, but lacks broadband, fast material quantification methods.
• Conventional THz time-domain spectroscopy (THz-TDS) faces calibration challenges, especially at non-resonant frequencies.

Purpose of the Study:

• To introduce a novel Rydberg-atom THz detector for rapid and quantitative material analysis.
• To demonstrate the detector's capability in measuring α-lactose monohydrate (α-LM) concentration.

Main Methods:

• Utilized Rydberg atoms excited to the 40D_5/2 state, creating an electromagnetically induced transparency (EIT) signal.
• Measured THz field strength via Autler-Townes (AT) doublet splitting, which is affected by sample attenuation.
• Compared results with conventional THz-TDS for validation.

Main Results:

• The Rydberg-atom detector accurately quantified α-LM concentration by correlating AT splitting intervals with sample concentration.
• Achieved excellent agreement with the Beer-Lambert law across a wide concentration range, even at 108.9 GHz (non-resonant frequency).
• Outperformed THz-TDS in establishing reliable calibration at non-resonant frequencies.

Conclusions:

• Rydberg-atom sensors provide a powerful, versatile tool for quantitative THz spectroscopy.
• This method eliminates the need for sample-specific absorption peaks and broad system bandwidth.
• Paves the way for advanced non-destructive testing and material analysis.