PiFM captures ultra-confined resonances and local field enhancement in hexagonal boron nitride optical nano-dipole antennae.
Unlike s-SNOM, PiFM works by mechanically detecting the gradient of the optical force generated by near fields on the AFM tip without the need for optical detection. The technique images the z-component of the field, which has the same distribution of the local charge density due to Gauss’s law.
The advantage of using PiFM is the acquisition of hyperspectral images of all the resonant modes in a structure with a single scan. Hyperspectral PiFM demonstrates excellent agreement between the theoretical simulations and the mapped resonance modes. See the amazing video of resonant phonon polaritons of RS1 band for various structures and wavelengths below. Link to all 4 videos are here.
The First 7 Resonant Modes in a Single Elliptical Hexagonal Boron Nitride
Optical Nano-dipole Antenna Arm
Hyperspectral PiFM for different wavelengths in the RS1 band. (Tamagnone et al., Sci. Adv. 2018; 4: eaat7189 15 June 2018 DOI: 10.1126/sciadv.aat7189)
To read more about these exciting advances, please see “Ultra-confined mid-infrared resonant phonon polaritons in van der Waals nanostructures” Tamagnone et al. Science Advances 15 Jun 2018: Vol. 4, no. 6, eaat7189 DOI: 10.1126/sciadv.aat7189