Robust terahertz self-heterodyne system using a phase noise compensation technique

Area of Science:

• Terahertz Science and Technology
• Optical Engineering
• Signal Processing

Background:

• Terahertz (THz) self-heterodyne systems are crucial for spectroscopy and imaging.
• Conventional systems face limitations due to phase noise from laser sources, degrading signal quality.
• Phase noise impacts the accuracy and stability of THz measurements.

Purpose of the Study:

• To propose and demonstrate a novel phase noise compensation technique for THz self-heterodyne systems.
• To improve the phase noise performance and reduce phase drift in THz measurements.
• To enhance the robustness and applicability of THz self-heterodyne systems.

Main Methods:

• Implementation of a phase noise compensation technique using an auxiliary photodiode and electric circuit.
• Subtraction of generated phase noise from the THz signal via a lock-in amplifier.
• Evaluation of phase noise and phase drift under open-air measurement conditions without strict temperature control.

Main Results:

• Achieved a phase noise standard deviation of 0.67 degrees without delay balance control.
• Demonstrated a phase drift of approximately 10 degrees under ambient temperature variations.
• Successfully compensated for laser source phase noise in the THz self-heterodyne system.

Conclusions:

• The proposed phase noise compensation technique significantly enhances THz self-heterodyne system performance.
• The system exhibits improved phase noise and reduced phase drift, making it more robust.
• This advancement enables more stable and accurate THz measurements in less controlled environments.