Electron-phonon interactions are fundamentally important physical processes responsible for many key discoveries in condensed matter physics and material sciences. Herein, by exploiting the scattering-type scanning near-field optical microscope (s-SNOM) excited with a femtosecond infrared (IR) laser, we explored strong coupling between IR phonons few-layer graphene (FLG) ultrahot electrons, whi...

Optical microresonators that are coupled to optical waveguides often behave quite similar to Fabry-Perot resonators. After summarising key properties of such resonators, three characterization methods will be discussed. The first involves the analysis of transmission and reflection spectra, from which important parameters like (waveguide) loss and coupling or reflection coefficients can be extr...

In order to investigate the suitability of random arrays of nanoparticles for plasmonic enhancement in the visible-near infrared range, we introduced three-dimensional scanning near-field optical microscopy (3D-SNOM) imaging as a useful technique to probe the intensity of near-field radiation scattered by random systems of nanoparticles at heights up to several hundred nm from their surface. We...

Optical metamaterials have unique properties which result from geometric confinement of the optical conductivity. We developed a series of infrared metasurfaces based on an array of metallic square loop antennas. The far-field absorption spectrum can be designed with resonances across the infrared by scaling the geometric dimensions. We measure the amplitude and phase of the resonant mode as st...

Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanor...

Holography has paved the way for phase imaging in a variety of wide-field techniques, including electron, X-ray and optical microscopy. In scanning optical microscopy, however, the serial fashion of image acquisition seems to challenge a direct implementation of traditional holography. Here we introduce synthetic optical holography (SOH) for quantitative phase-resolved imaging in scanning optic...

Polaritons allow for strong light-matter coupling and highly sensitive analysis of (bio)chemical substances processes. Nanoimaging the polaritons’ evanescent fields is critically important experimental mode identification field confinement studies. Here we describe two setups polariton nanoimaging spectroscopy in liquid. We first demonstrate mapping localized plasmon polaritons metal antennas w...

Scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared nanospectroscopy (nano-FTIR) are emerging tools for nanoscale chemical material identification. Here, we push s-SNOM and nano-FTIR one important step further by enabling them to quantitatively measure local dielectric constants and infrared absorption. Our technique is based on an analytical model, wh...

We present an experimental study of the coupling of light from a probe of a scanning near-field optical microscope ~SNOM! into a mesoscopic structure consisting of gold stripes with varying separations. We demonstrate that the coupling efficiency depends upon the polarization direction in the probe relative to the stripes as well as the separation between the lines. Two possible explanations fo...