Continuous-wave terahertz field imaging based on photonics-based self-heterodyne electro-optic detection

Area of Science:

• Photonics
• Terahertz (THz) Imaging
• Electro-optic Measurement

Background:

• Terahertz (THz) imaging requires precise measurement of field amplitude and phase.
• Traditional THz imaging techniques often rely on complex setups involving mechanical delay lines or phase-locked synthesizers, limiting system simplicity and accessibility.

Purpose of the Study:

• To demonstrate a novel photonics-based self-heterodyne electro-optic field imaging technique for THz frequencies.
• To simplify THz field imaging by eliminating the need for mechanical delay lines and phase-locked synthesizers.
• To achieve simultaneous amplitude and phase imaging of THz fields with improved system simplicity.

Main Methods:

• Utilizing an optical intensity beat generated by mixing two frequency-detuned free-running lasers for both THz generation and detection.
• Employing an optical frequency shifter to shift the beat frequency for coherent heterodyne measurement with free-running lasers.
• Implementing a photonics-based self-heterodyne approach for electro-optic field imaging.

Main Results:

• Successfully demonstrated simultaneous amplitude and phase imaging of a 125 GHz THz field radiated from a horn antenna.
• Achieved a standard deviation of 0.18 radians for phase measurements, indicating high precision.
• Validated the effectiveness of the photonics-based self-heterodyne technique in simplifying THz imaging systems.

Conclusions:

• The developed photonics-based self-heterodyne technique offers a simplified and effective approach for THz field imaging.
• The elimination of mechanical delay lines and phase-locked synthesizers significantly enhances system simplicity.
• This technique provides a promising pathway for advanced THz applications requiring precise amplitude and phase information.