Laser THz emission nanoscopy and THz nanoscopy

Area of Science:

• Terahertz spectroscopy
• Near-field microscopy
• Condensed matter physics

Background:

• Scattering-type scanning near-field optical microscopy (s-SNOM) enables nanoscale optical investigations.
• Terahertz (THz) spectroscopy is crucial for probing charge carrier dynamics in materials.

Purpose of the Study:

• To experimentally and theoretically compare THz nanoscopy and laser terahertz emission nanoscopy (LTEN).
• To demonstrate the complementary information obtainable from these s-SNOM techniques for charge carrier analysis.
• To investigate THz near-field confinement and develop predictive models.

Main Methods:

• Utilized nanoscale reflection-type THz time-domain spectroscopy (THz nanoscopy).
• Employed nanoscale laser THz emission nanoscopy (LTEN).
• Developed a computational approach for electric field confinement and applied the finite dipole model (FDM).

Main Results:

• Achieved THz nanoscopy and LTEN imaging with high harmonic demodulation (up to 6th and 10th, respectively).
• Demonstrated THz near-field confinement down to 11 nm.
• Computational analysis revealed effective 'tip sharpening' in LTEN due to geometry and nonlinearity.
• Validated the finite dipole model for predicting broadband scattered THz fields and LTEN near-field response.

Conclusions:

• THz nanoscopy and LTEN offer complementary insights into material charge carriers.
• LTEN exhibits enhanced spatial resolution due to its unique generation mechanism and probe geometry.
• The finite dipole model is a valuable tool for simulating and understanding THz near-field interactions in s-SNOM.