Superfocusing of terahertz wave through spoof surface plasmons

Area of Science:

• Physics
• Electromagnetism
• Nanotechnology

Background:

• Terahertz (THz) waves offer unique properties for imaging and sensing.
• Achieving subwavelength focusing of THz waves remains a challenge.
• Spoof surface plasmons (SSP) provide a route to manipulate THz waves at the subwavelength scale.

Purpose of the Study:

• To propose and numerically demonstrate a novel method for superfocusing terahertz waves.
• To engineer field patterns for enhanced radiationless electromagnetic interference (REI) focusing.
• To investigate the potential for superfocusing using ultra-thin metallic gratings.

Main Methods:

• Utilizing modified subwavelength metallic gratings to generate spoof surface plasmons (SSP).
• Leveraging Fabry-Perot resonances for near-field rapid oscillation formation.
• Engineering groove width and grating number to control phase and amplitude modulation.
• Evaluating focusing performance using full-width-half-maximum (FWHM) beamwidth and superfocusing metric.

Main Results:

• Achieved a superfocusing metric of 1.67 with optimized Fabry-Perot resonance (seventh order).
• Obtained a FWHM beamwidth of 0.06λ at a distance of 0.1λ, a 540% improvement over a single slit.
• Demonstrated focusing capability on ultra-thin metallic gratings.
• Verified two-dimensional subwavelength focusing behavior numerically.

Conclusions:

• The proposed method enables significant superfocusing of terahertz waves.
• This technique offers potential for enhanced resolution in THz sensing and super-resolution imaging.
• The ability to maintain focusing on ultra-thin structures broadens practical applications.