Directional Coupling to a λ/5000 Nanowaveguide.

Area of Science:

• Terahertz (THz) technology
• Nanophotonics
• Plasmonics

Background:

• Silicon microdevices offer practical THz technologies due to low loss and fabrication ease.
• Diffraction limits conventional devices to hundreds of micrometers, hindering nanoscale THz applications.
• Efficiently coupling to nanoscale metallic gap modes for THz confinement is challenging.

Purpose of the Study:

• To demonstrate an efficient strategy for interfacing subterahertz radiation with nanoscale waveguides.
• To overcome diffraction limitations for nanoscale terahertz applications.
• To enable tailored and controllable interfacing of millimeter waves with nanoscale waveguides.

Main Methods:

• Fabrication of a 200 nm wide nanogap waveguide in a gold film.
• Utilizing phase matching between dielectric and nanogap waveguide modes for directional coupling.
• Conducting broadband far-field terahertz transmission and near-field measurements.

Main Results:

• Demonstrated efficient coupling of subterahertz radiation (1 mm wavelength) to a 200 nm nanogap waveguide.
• Observed a transmission dip due to resonant coupling, indicating power transfer to the nanogap.
• Achieved an estimated coupling efficiency of approximately 10% from dielectric to nanogap waveguide.

Conclusions:

• Presented a novel method for interfacing millimeter waves with nanoscale waveguides.
• The approach overcomes diffraction limits, enabling nanoscale terahertz device footprints.
• Potential applications include on-chip nanospectroscopy, telecommunications, and quantum technologies.