Label-free incoherent super-resolution optical microscopy

TL;DR

This paper introduces EPSLON, a novel label-free super-resolution microscopy technique that uses silicon nitride waveguide photoluminescence to achieve near-field illumination, enabling super-resolution imaging without fluorescent labels.

Contribution

The study proposes a new physics-based methodology to overcome the diffraction limit in label-free incoherent optical microscopy using evanescent photoluminescence from silicon nitride waveguides.

Findings

Demonstrated label-free super-resolution imaging with SIM and IFON techniques.

Showed that silicon nitride waveguide photoluminescence mimics fluorescent molecule kinetics.

Achieved stable, linear, and time-invariant illumination for super-resolution microscopy.

Abstract

The photo-kinetics of fluorescent molecules have enabled the circumvention of far-field optical diffraction-limit. Despite its enormous potential, the necessity to label the sample may adversely influence the delicate biology under investigation. Thus, continued development efforts are needed to surpass the far-field label-free diffraction barrier. The coherence of the detected light in label-free mode hinders the application of existing super-resolution methods based on incoherent fluorescence imaging. In this article, we present the physics and propose a methodology to circumvent this challenge by exploiting the photoluminescence of silicon nitride waveguides for near-field illumination of unlabeled samples. The technique is abbreviated EPSLON, Evanescently decaying Photoluminescence Scattering enables Label-free Optical Nanoscopy. We demonstrate that such an illumination has properties that mimic the photo-kinetics of nano-sized fluorescent molecules. This allows for developing a label-free incoherent system that is linear in intensity, and stable with time thereby permitting the application of techniques like structured illumination microscopy (SIM) and intensity-fluctuation-based optical nanoscopy (IFON) in label-free mode to circumvent the diffraction limit.