Angle-Controlled Nanospectrum Switching from Lorentzian to Fano Lineshapes

Area of Science:

• Nanophotonics
• Terahertz (THz) Spectroscopy
• Metamaterials

Background:

• Tunable spectral lineshapes are crucial for nanoscale photonic technologies.
• Conventional far-field methods struggle with nanoscale phenomena, especially in the THz range.

Purpose of the Study:

• To precisely modulate spectral lineshapes (Lorentzian, Fano, antiresonance) at the nanoscale.
• To investigate the physical mechanisms behind these spectral transitions using THz scattering scanning near-field optical microscopy (s-SNOM).

Main Methods:

• Utilized a U-shaped resonant ring on a waveguide substrate.
• Employed THz scattering scanning near-field optical microscopy (s-SNOM) for nanoscale analysis.
• Analyzed time-domain phase shifts between waveguide excitation and ring resonance.

Main Results:

• Achieved precise control over Lorentzian, Fano, and antiresonance profiles.
• Identified time-domain phase shifts as the driving mechanism for spectral transitions.
• Observed nanoscale asymmetry in near-field response, undetectable by far-field methods.

Conclusions:

• Demonstrated a novel method for nanoscale spectral lineshape control.
• Highlighted the potential for characterizing nanoresonators and developing nanoscale phase sensors.
• Emphasized the superiority of s-SNOM for revealing nanoscale optical phenomena.