Simulations of a Dielectric Slot Tip for Scanning Near-Field Microwave Microscope

In order to study possible ways for improving the throughput and resolution of Scanning Near-Field Optical Microscope (SNOM) tips we set up a Scanning Near-Field Microwave Microscope (SNMM) with geometry similar to tapered, coated fiber tips that are frequently used in SNOM. In order to obtain the desired improvement, we introduce slits in the cladding and attach a small metallic tip. These modifications allow us to obtain a mode conversion from linearly polarized fiber modes to rotationally-symmetric wire modes that provide a very high resolution better than 1/800 of the wavelength at 10 GHz. The microwave measurements are supported by full 3D simulations based on a finite elements solver.