Label-Free Optical Nanoscopy of Single-Layer Graphene

Abstract

The application of ultrafast pulsed laser sources and spectroscopic techniques enables label-free, deep-tissue optical microscopy. However, circumvention of the diffraction limit in this field is still an open challenge. Among such approaches, pump–probe microscopy is of increasing interest thanks to its highly specific nonfluorescent-based contrast mechanisms for the imaging of material and life science samples. In this paper, a custom femtosecond-pulsed near-infrared pump–probe microscope, which exploits transient absorption and stimulated Raman scattering interactions, is presented. The conventional pump–probe configuration is combined with a spatially shaped saturation pump beam, which allows for the reduction of the effective focal volume exploiting transient absorption saturation. By optimizing the acquisition parameters, such as power and temporal overlap of the saturation beam, we can image single-layer graphene deposited on a glass surface at the nanoscale and with increased layer sensitivity. These results suggest that saturation pump–probe nanoscopy is a promising tool for label-free high-resolution imaging.

Characterization of nanosensitive multifractality in submicron scale tissue morphology and its alteration in tumor progression

“…Recently, many optical nanoscopic techniques were developed based on labeling [1][2][3][4][5][6] and are limited to superficial imaging. [7][8][9][10][11][12][13] It is a challenging task for researchers to develop a diagnostic system that can provide label-free depth-resolved detection. There are few early developments that demonstrated averaged nanosensitive structural detection over a volume-rather than depth-resolved detection.…”

Optical nanoscopy

“…26. Moreover, due to the high laser intensity and architecture flexibility, such set-up is also suitable for second harmonic generation [80], pump-probe [81] and Mueller matrix [82] microscopy. Figure 27 shows the combined images.…”

Editorial: Advances in Label Free Tissue Imaging With Laser Scanning Microscopy Techniques

“…In the opinion of many, these techniques, together with investigations approaches based on their combined use, will soon become the central element of the default tissue characterization frameworks for both ex vivo and in vivo assays. Furthermore, emerging LSM techniques exploiting various ingenious strategies to achieve superresolved images in a label-free manner [9][10][11][12] are also likely to be transferred soon toward applications addressing tissue imaging.…”