Apertureless near-field optical microscopy

Abstract

We discuss the operating principles of the apertureless scanning near-field optical microscope (ASNOM), in which the probe acts as a rod antenna and its electromagnetic radiation plays the role of the registered signal. The phase and amplitude of the emitted wave vary depending on the ‘grounding conditions’ of the antenna tip at the sample point under study. Weak radiation from a tiny (2–15 μm long) tip is detected using optical homo- and heterodyning and the nonlinear dependence of the tip polarizability on the tip–surface distance. The lateral resolution of ASNOMs is determined by the tip curvature radius (1– 20 nm), regardless of the wavelength (500 nm–100 μm). ASNOMs are shown to be capable of providing a surface optical map with nanometer resolution and carrying out spectral- and time-resolved measurements at a selected point on the surface.

Near-Field Plasmonic Probe with Super Resolution and High Throughput and Signal-to-Noise Ratio

“…Spatially resolving objects at the nanoscale satisfies a wide range of demands in science and technology. To fulfill such demands, near-field scanning optical microscopy (NSOM) is a powerful technique that simultaneously enables optical imaging, spectroscopic analysis and chemical identification beyond the diffraction limit. − To date, there are two major types of NSOM tips: an aperture-type tip (a-tip) and a scattering-type tip (s-tip; also known as an apertureless-type tip). The a-tip is constructed by introducing a tiny aperture to a fiber taper or to the tip apex of an atomic force microscope (AFM) probe.…”

Photoinduced force microscopy as a novel method for the study of microbial nanostructures

“…So, an important advantage of PiFM over these applications is its high spectral resolution of 1 cm −1 , which can assist in the deconvolution of fine spectral components, which are lost in the 8 cm −1 resolution found in AFM-IR in these applications. 40,41 Table 1 A comparison between the operation modes and resolution of AFM-IR (atomic force microscope-infrared spectroscopy), PiFM and s-SNOM (scattering scanning near-field optical microscopy) AFM-IR 32 PiFM 24,29 s-SNOM 33 Operating mode…”

Topography-induced variations of localized surface plasmon resonance in tip-enhanced Raman configuration

“…[4,5] In order to overcome this limitation, techniques such as apertureless scanning near-field optical microscopy (aSNOM) were developed. [6] aSNOM combines the high spatial resolution of conventional scanning probe microscopy (SPM) with the high sensitivity of surface enhanced optical analysis. [7,8] In our previous work, we used aSNOM to image changes in average refractive index of a variety of materials at the nanoscale.…”