Contrast enhancement of microsphere-assisted super-resolution imaging in dark-field microscopy

Abstract

We report a method of boosting the imaging contrast of microsphere-assisted super-resolution visualization by utilizing dark-field illumination (DFI). We conducted experiments on both 10-µm-diameter silica (SiO2) microspheres with refractive index n ∼ 1.46 under no and partial immersion in ethyl alcohol (n ∼ 1.36) and 20-µm-diameter barium titanate glass (BTG, n ∼ 1.9) microspheres with full immersion to show the super-resolution capability. We experimentally demonstrated that the imaging contrast and uniformity were extraordinarily improved in the DFI mode. The intensity profiles in the visualization also numerically confirm the enhanced sharpness for a better imaging quality when applying DFI.

All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

“…More systematic studies as well as the applications of microsphere-based (or the derivatives of microspheres such as liquid droplets and microbers) imaging can be found extensively in the mainstream optics and photonics journals. 48,[180][181][182][183][184][185][186][187][188] Different than other super-resolution imaging techniques like hyperlens and superlens, [189][190][191] super-oscillation lens, 17,[192][193][194] and uorescence-based modalities, 195,196 the underlying physics of imaging beyond the Rayleigh limit via dielectric microspheres has not been completely revealed yet, although there was a study that claimed that it is due to the FWHM of PNJs. 31 Maslov et al investigated the theoretical limits of resolution available in microsphere-based nanoscopy using incoherent point emitters in the air.…”

Selecting a Proper Microsphere to Combine Optical Trapping with Microsphere-Assisted Microscopy

“…Besides these techniques, in 2011, an optical microscope aided by fused silica (SiO 2 ) microspheres with low index ( n ∼ 1.46) in air was used to achieve 100-nm-resolution imaging under white light illumination [6], and the observation power of microscopes was enhanced greatly. The microscopy assisted by index-different microspheres, typically the SiO 2 , polystyrene (PS), melamine formaldehyde (MF), barium titanate glass (BTG) microsphere, demonstrates the feasibility to realize super-resolution imaging of nanostructures and biological samples in different conditions [7][8][9][10][11][12]. Many other non-spherical and non-symmetrical particle-lens have also been investigated [13,14], and the main advantage of a sphere is that it can achieve ultra-sharp focusing of the incoming wave to generate extreme spatial field localization.…”

Coated High-Refractive-Index Barium Titanate Glass Microspheres for Optically Trapped Microsphere Super-Resolution Microscopy: A Simulation Study

“…Darafsheh et al realized optical super-resolution imaging by using high-refractive-index barium titanate glass (BTG) microspheres ( n ∼ 1.9-2.1) totally immersed in a liquid environment [8], and they also studied the influence of immersion medium on imaging performance in microsphere-assisted microscopy [9]. This label-free super-resolution imaging technique has attracted many research groups across the world, demonstrating sub-diffraction discerning ability in nanostructure detections and biological observations [10][11][12][13]. The super-resolution mechanism of microsphere-assisted microscopy is still a heated topic [14][15][16].…”