Nanoscale mapping of refractive index by using scattering-type scanning near-field optical microscopy

Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering

“…While the AFM images reveal the topography of the sample surface, the s-SNOM images (amplitude and phase) reveal the optical properties of the samples. According to the general conception, the amplitude signal is linked to the dispersion, while the phase signal is linked to the optical absorption [34,35]. The surfaces of HEF samples deposited at room temperature with the power of 300 W (sample #2) and at 350 °C with the power of 100 W (sample #5) have similar morphologies, which consist of round particles of small sizes (Figure 6a,c).…”

Correlative imaging of biological tissues with apertureless scanning near-field optical microscopy and confocal laser scanning microscopy

“…In the collected s-SNOM amplitude and phase images optical signal variations can be perceived across the surface of the imaged melanin granules. These variations can be exploited for quantitatively assessing variations in the dielectric function [15], and hence optical parameters such as refractive index [33], transmittance, absorption, etc., which are important for practical applications requiring the prediction of light transport through pigmented tissue [34]. s-SNOM images based on amplitude and phase contrast are correlated but contain nonetheless complementary information [12] and simultaneous mapping of amplitude and phase of the near-field scattered light can be exploited to obtain both real and imaginary parts of the refractive index or the dielectric permittivity [15,33].…”

“…These variations can be exploited for quantitatively assessing variations in the dielectric function [15], and hence optical parameters such as refractive index [33], transmittance, absorption, etc., which are important for practical applications requiring the prediction of light transport through pigmented tissue [34]. s-SNOM images based on amplitude and phase contrast are correlated but contain nonetheless complementary information [12] and simultaneous mapping of amplitude and phase of the near-field scattered light can be exploited to obtain both real and imaginary parts of the refractive index or the dielectric permittivity [15,33]. Furthermore, s-SNOM phase images are less prone to "edge darkening" artifacts which can occur in s-SNOM amplitude images at the locations of sharp topographical steps where weaker scattering is exhibited as a result of increased distance between the tip and the sample [35].…”

“…In this regard, in a set of future experiments we plan to replace CLSM with MPM and use Two-Photon Excitation Fluorescence (TPEF) and Second Harmonic Generation (SHG) in combination with s-SNOM to image unlabeled ocular and epithelial tissues. The three techniques have a complementary usefulness in imaging non-labeled biological specimens: (i) TPEF can be used to probe the autofluorescence generated by endogenous chromophores, such as the enzyme cofactors nicotinamide adenine dinucleotide or flavin adenine dinucleotide, (ii) SHG can collect optical signals generated from non-centrosymetric molecules present in animal tissues, such as myosin, tubulin or collagen, while (iii) s-SNOM can provide valuable information based on dielectric contrast, and can quantitatively assess optical properties such as refractive index, absorption, etc [15,33].…”

Improved Point Dipole Model for Subwavelength Resolution Scattering Near-Field Optical Microscopy (SNOM)

“…Recently, the high spatial resolution of SNOM, which is independent of wavelength, has been implemented in various practical applications, such as nanoscale vibration spectroscopy [3], identification of the material type according to the SNOM image on the edge of the sample [4], nanoimaging of plasma polaritons in nanostructures, such as graphene-layered structure [5][6][7][8][9] and nanoantennas [10,11], contrast and imaging performance in photo-induced force microscopy [12], quantitative measurement of nano-optical properties [13,14], sensitivity of SNOM nanometer imaging with temperature [15], and tomographic NF imaging [16][17][18].…”