Self-referenced single-shot THz detection.

Area of Science:

• Terahertz (THz) spectroscopy and detection
• Optics and photonics
• Materials science

Background:

• Terahertz time-domain spectroscopy (THz-TDS) is a powerful tool for material characterization.
• Shot-to-shot fluctuations in laser pulses are a major source of noise in single-shot THz detection.
• Existing noise reduction methods, like polarization-gated balanced detection, can be complex or limited.

Purpose of the Study:

• To introduce a novel self-referencing method for reducing noise in single-shot terahertz detection.
• To demonstrate the effectiveness of this method in achieving a low noise floor.
• To validate the method's capability for precise material property measurements.

Main Methods:

• A single terahertz (THz) pulse was split using a reflective echelon to generate simultaneous signal and reference waveforms.
• Correlation function based referencing was employed, independent of polarization states.
• The DC conductivity of a 30 nm free-standing gold film was measured using a single THz pulse.

Main Results:

• The self-referencing scheme significantly reduced noise originating from shot-to-shot fluctuations.
• The achieved noise floor was comparable to state-of-the-art polarization-gated balanced detection.
• The measured DC conductivity of gold (σ₀ = 1.3 ± 0.4 × 10⁷ S m⁻¹) agreed well with four-point probe measurements.

Conclusions:

• The developed self-referencing method offers a robust and effective way to minimize noise in single-shot THz detection.
• This technique is versatile and not limited by polarization dependencies.
• The method shows significant potential for accurate characterization of dynamical changes and small signals in materials.