A terahertz broadband 3 dB directional coupler based on bridged PPDW

Area of Science:

• Electromagnetics and Wave Propagation
• Microwave and Terahertz Engineering
• Integrated Photonics

Background:

• Parallel plate dielectric waveguides (PPDWs) are essential components in microwave and terahertz systems.
• Conventional PPDW couplers often suffer from limited bandwidth and large footprints.
• There is a need for compact, high-performance directional couplers for terahertz applications.

Purpose of the Study:

• To propose and demonstrate a novel broadband 3 dB directional coupler using a bridged PPDW structure.
• To achieve very flat coupling and high performance at terahertz frequencies.
• To enhance bandwidth, isolation, and reduce the physical size compared to conventional designs.

Main Methods:

• A bridge structure was introduced in the uniform coupling section between two PPDWs.
• Quarter-circle bend arms were employed as transition sections for improved isolation and reduced reflections.
• The design was optimized for operation at terahertz frequencies, specifically around 1 THz.

Main Results:

• The bridged PPDW coupler achieved broadband 3 dB coupling with a uniform coupling length of only 400 μm.
• Excellent performance metrics were obtained: average return loss > 28 dB, average isolation > 27 dB, and average insertion loss of 0.9 dB.
• A significant increase in bandwidth (4.2 times) and a reduction in uniform coupling length (61%) were observed compared to conventional PPDW couplers.
• The device demonstrated a percentage bandwidth of 12.5% at 1 THz.

Conclusions:

• The proposed bridged PPDW directional coupler offers a significant advancement in terahertz component technology.
• Its broadband characteristics, compact size, and mechanical stability make it suitable for terahertz integrated circuits and systems.
• This novel design paves the way for more efficient and versatile terahertz applications.