Total internal reflection-based extractor and collimator of terahertz radiation

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Terahertz Technology

Background:

• Photoconductive antennas are crucial for generating terahertz (THz) radiation.
• Efficient extraction and collimation of THz radiation from semiconductor substrates remain a challenge.
• Existing methods often suffer from low efficiency and poor beam quality.

Purpose of the Study:

• To design and model a novel optical element for enhanced THz radiation extraction and collimation.
• To improve the efficiency and beam quality of THz radiation from photoconductive antennas.
• To investigate the performance of a truncated silicon paraboloid for THz beam shaping.

Main Methods:

• Design of a truncated silicon paraboloid optical element.
• Utilizing geometrical optics for initial calculations.
• Employing finite-difference time-domain (FDTD) modeling for detailed simulation.
• Analyzing terahertz energy transmission and beam characteristics.

Main Results:

• The designed element is a truncated silicon paraboloid (1-2 cm length).
• Total internal reflection within the paraboloid efficiently directs THz radiation.
• The output is a collimated beam (5-7 mm diameter) with a flat wavefront.
• High terahertz energy transmission efficiency of approximately 70% was achieved.
• Approximately 90% of the transmitted energy was contained within the collimated beam.

Conclusions:

• The truncated silicon paraboloid is an effective optical element for THz radiation management.
• This design significantly improves the extraction and collimation efficiency of THz beams.
• The developed method offers a promising solution for high-quality THz beam generation in scientific and technological applications.