A Novel 3D Probe for Near-Field Scanning Microwave Microscopy

Area of Science:

• Applied Physics
• Materials Science
• Electromagnetism

Background:

• Near-field scanning microwave microscopy (NSMM) faces challenges in achieving high resolution over practical scan areas.
• Existing NSMM techniques are limited by the classical Abbe diffraction limit.

Purpose of the Study:

• To introduce a novel three-dimensional (3D) NSMM probe for enhanced electromagnetic property probing.
• To investigate how probe geometry influences spatial resolution and image fidelity.

Main Methods:

• Development of a 3D NSMM probe using a split-ring resonator (SRR) coupled to a microstrip line and loaded with metallic bars.
• Full-wave numerical simulations to extract the field-spread function (FSF) and analyze spatial-frequency content.
• Fabrication using printed circuit board (PCB) technology and experimental validation.

Main Results:

• The 3D probe design enhances electric-field localization via field singularities.
• Simulations demonstrated that localized FSFs improve image fidelity and preserve higher spatial frequencies.
• Experimental imaging of a dielectric slab with a void showed good agreement with the convolution model.

Conclusions:

• The proposed 3D SRR-based probe acts as a spatial filter, enabling higher resolution in NSMM imaging.
• Engineered near-field distribution is key to overcoming diffraction limits.
• The probe design offers a pathway to improved nanoscale electromagnetic characterization.