205-240  GHz free-space-to-fiber mode adapter with an 80% mode conversion efficiency

Area of Science:

• Optics and Photonics
• Terahertz Technology
• Fiber Optics

Background:

• Efficient coupling of broadband terahertz (THz) radiation into hollow-core fibers (HCFs) is crucial for THz applications.
• Existing methods often suffer from low efficiency or narrow bandwidth.
• The TE01 mode is desirable for low-loss propagation in HCFs.

Purpose of the Study:

• To propose and simulate an integrated terahertz mode adapter for efficient free-space to HCF coupling.
• To achieve high mode conversion efficiency from a Gaussian beam to the TE01 mode in HCF.
• To ensure a broadband operating capability for the developed adapter.

Main Methods:

• Design of an integrated adapter comprising a pyramidal horn antenna, a broadband mode converter, and a conical horn.
• Electromagnetic simulations to analyze the coupling efficiency and mode conversion.
• Characterization of the adapter's performance across a range of terahertz frequencies.

Main Results:

• The proposed terahertz mode adapter demonstrates a high mode conversion efficiency of up to 80% for Gaussian beam to TE01 mode.
• Simulations confirm efficient excitation of the TE01 mode in the hollow-core fiber.
• A wide operating bandwidth exceeding 15.7% (205-240 GHz) was achieved.

Conclusions:

• The integrated terahertz mode adapter offers a promising solution for efficient broadband THz coupling into HCFs.
• The high conversion efficiency and wide bandwidth pave the way for advanced THz communication and sensing systems.
• The adapter design is validated through simulation, showing significant potential for experimental implementation.