3D point scanning super-resolution microscopy via polarization modulation

Analysis and verification of fluorescence super-resolution microscopy via polarization modulation in reciprocal space

Based on the polarization property of fluorescent dipoles, fluorescence super-resolution microscopy recently has been proposed by modulating the polarization of the excitation light. In this technique, the super-resolution image is reconstructed by processing the polarization-modulated fluorescence image stack with an iteration algorithm. However, the mechanism of resolution improvement by polarization modulation has been questioned. In this paper, the mechanism of resolution enhancement by polarization modulation is analyzed in reciprocal space. The mathematical model and the reconstruction algorithm of fluorescence super-resolution microscopy via polarization modulation are proposed in reciprocal space. The corresponding simulation results and analysis show that polarization modulation can enlarge the highest detected spatial frequency of fluorescence microscopy to achieve super resolution, which verifies the role of polarization modulation in resolution improvement and provides a useful reference to study fluorescence super-resolution microscopy via polarization modulation in reciprocal space.

Polarized resonant emission of monolayer WS2 coupled with plasmonic sawtooth nanoslit array

Transition metal dichalcogenide (TMDC) monolayers have enabled important applications in light emitting devices and integrated nanophotonics because of the direct bandgap, spin-valley locking and highly tunable excitonic properties. Nevertheless, the photoluminescence polarization is almost random at room temperature due to the valley decoherence. Here, we show the room temperature control of the polarization states of the excitonic emission by integrating WS₂ monolayers with a delicately designed metasurface, i.e. a silver sawtooth nanoslit array. The random polarization is transformed to linear when WS₂ excitons couple with the anisotropic resonant transmission modes that arise from the surface plasmon resonance in the metallic nanostructure. The coupling is found to enhance the valley coherence that contributes to ~30% of the total linear dichroism. Further modulating the transmission modes by optimizing metasurfaces, the total linear dichroism of the plasmon-exciton hybrid system can approach 80%, which prompts the development of photonic devices based on TMDCs.

Here the authors show that WS₂ coupled with a plasmonic sawtooth nanoslit array is an efficient exciton-plasmon hybrid system which enables polarization modulation of the excitonic emission at the nanoscale up to 80% and observation of valley coherence at room temperature.

Three-dimensional super-resolved live cell imaging through polarized multi-angle TIRF

Measuring three-dimensional nanoscale cellular structures is challenging, especially when the structure is dynamic. Owing to the informative total internal reflection fluorescence (TIRF) imaging under varied illumination angles, multi-angle (MA) TIRF has been examined to offer a nanoscale axial and a subsecond temporal resolution. However, conventional MA-TIRF still performs badly in lateral resolution and fails to characterize the depth image in densely distributed regions. Here, we emphasize the lateral super-resolution in the MA-TIRF, exampled by simply introducing polarization modulation into the illumination procedure. Equipped with a sparsity and accelerated proximal algorithm, we examine a more precise 3D sample structure compared with previous methods, enabling live cell imaging with a temporal resolution of 2 s and recovering high-resolution mitochondria fission and fusion processes. We also shared the recovery program, which is the first open-source recovery code for MA-TIRF, to the best of our knowledge.