Glass fibres with silicon cores have emerged as a versatile platform for all-optical processing, sensing and microscale optoelectronic devices. Using SiGe in the core extends the accessible wavelength range and potential optical functionality because the bandgap and optical properties can be tuned by changing the composition. However, silicon and germanium segregate unevenly during non-equilibrium solidification, presenting new fabrication challenges, and requiring detailed studies of the alloy crystallization dynamics in the fibre geometry. We report the fabrication of SiGe-core optical fibres, and the use of CO 2 laser irradiation to heat the glass cladding and recrystallize the core, improving optical transmission. We observe the ramifications of the classic models of solidification at the microscale, and demonstrate suppression of constitutional undercooling at high solidification velocities. Tailoring the recrystallization conditions allows formation of long single crystals with uniform composition, as well as fabrication of compositional microstructures, such as gratings, within the fibre core.

Optical nanoscopy techniques can image intracellular structures with high specificity at sub-diffraction limited resolution, bridging the resolution gap between optical microscopy and electron microscopy. So far conventional nanoscopy lacks the ability to generate high throughput data, as the imaged region is small. Photonic chip-based nanoscopy has demonstrated the potential for imaging large areas, but at a lateral resolution of 130 nm. However, all the existing super-resolution methods provide a resolution of 100 nm or better. In this work, chip-based nanoscopy is demonstrated with a resolution of 75 nm over an extraordinarily large area of 0.5 mm x 0.5 mm, using a low magnification and high N.A. objective l ens. Furthermore, the performance of chip-based nanoscopy is benchmarked by studying the localization precision and illumination homogeneity for different waveguide widths. The advent of large field-of-view chip-based nanoscopy opens up new routes in diagnostics where high throughput is needed for the detection of non-diffuse disease, or rare events such as the early detection of cancer.

Blood analysis is an important diagnostic tool, as it provides a wealth of information about the patient's health. Raman spectroscopy is a promising tool for blood analysis, but widespread clinical application is limited by its low signal strength, as well as complex and costly instrumentation. The growing field of waveguide-based Raman spectroscopy tries to solve these challenges by working toward fully integrated Raman sensors with increased interaction areas. In this letter, we demonstrate resonance Raman measurements of hemoglobin, a crucial component of blood, at 532-nm excitation using a tantalum pentoxide (Ta 2 O 5) waveguide platform. We have also characterized the background signal from Ta 2 O 5 waveguide material when excited at 532 nm. In addition, we demonstrate spontaneous Raman measurements of isopropanol and methanol using the same platform. Our results suggest that Ta 2 O 5 is a promising waveguide platform for resonance Raman spectroscopy at 532 nm and, in particular, for blood analysis.

Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced contrast due to optical sectioning. The conventional approach is to use high numerical aperture microscope TIRF objectives for both excitation and collection, severely limiting the field of view and throughput. We present a novel approach to generating TIRF excitation for imaging with optical waveguides, called chip-based nanoscopy. The aim of this protocol is to demonstrate how chip-based imaging is performed in an already built setup. The main advantage of chip-based nanoscopy is that the excitation and collection pathways are decoupled. Imaging can then be done with a low magnification lens, resulting in large field of view TIRF images, at the price of a small reduction in resolution. Liver sinusoidal endothelial cells (LSECs) were imaged using direct stochastic optical reconstruction microscopy (dSTORM), showing a resolution comparable to traditional super-resolution microscopes. In addition, we demonstrate the high-throughput capabilities by imaging a 500 µm x 500 µm region with a low magnification lens, providing a resolution of 76 nm. Through its compact character, chip-based imaging can be retrofitted into most common microscopes and can be combined with other on-chip optical techniques, such as on-chip sensing, spectroscopy, optical trapping, etc. The technique is thus ideally suited for high throughput 2D super-resolution imaging, but also offers great opportunities for multimodal analysis.

Histology involves the observation of structural features in tissues using a microscope. While diffraction-limited optical microscopes are commonly used in histological investigations, their resolving capabilities are insufficient to visualize details at subcellular level. Although a novel set of super-resolution optical microscopy techniques can fulfill the resolution demands in such cases, the system complexity, high operating cost, lack of multi-modality, and low-throughput imaging of these methods limit their wide adoption for histological analysis. In this study, we introduce the photonic chip as a feasible high-throughput microscopy platform for super-resolution imaging of histological samples. Using cryopreserved ultrathin tissue sections of human placenta, mouse kidney, pig heart, and zebrafish eye retina prepared by the Tokuyasu method, we demonstrate diverse imaging capabilities of the photonic chip including total internal reflection fluorescence microscopy, intensity fluctuation-based optical nanoscopy, single-molecule localization microscopy, and correlative light-electron microscopy. Our results validate the photonic chip as a feasible imaging platform for tissue sections and pave the way for the adoption of super-resolution high-throughput multimodal analysis of cryopreserved tissue samples both in research and clinical settings.