Strong focusing on diffraction-limited spots is essential for many photonic applications and is particularly relevant for optical trapping; however, all currently used approaches fail to simultaneously provide flexible transportation of light, straightforward implementation, compatibility with waveguide circuitry, and strong focusing. Here, we demonstrate the design and 3D nanoprinting of an ultrahigh numerical aperture meta-fibre for highly flexible optical trapping. Taking into account the peculiarities of the fibre environment, we implemented an ultrathin meta-lens on the facet of a modified single-mode optical fibre via direct laser writing, leading to a diffraction-limited focal spot with a record-high numerical aperture of up to NA ≈ 0.9. The unique capabilities of this flexible, cost-effective, bio- and fibre-circuitry-compatible meta-fibre device were demonstrated by optically trapping microbeads and bacteria for the first time with only one single-mode fibre in combination with diffractive optics. Our study highlights the relevance of the unexplored but exciting field of meta-fibre optics to a multitude of fields, such as bioanalytics, quantum technology and life sciences.

A significant improvement in acquisition speed of structured illumination microscopy (SIM) opens a new field of applications to this already well-established super-resolution method towards 3D scanning real-time imaging of living cells. We demonstrate a method of increased acquisition speed on a two-beam SIM fluorescence microscope with a lateral resolution of ~100 nm at a maximum raw data acquisition rate of 162 frames per second (fps) with a region of interest of 16.5  ×  16.5 µm, free of mechanically moving components. We use a programmable spatial light modulator (ferroelectric LCOS) which promises precise and rapid control of the excitation pattern in the sample plane. A passive Fourier filter and a segmented azimuthally patterned polarizer are used to perform structured illumination with maximum contrast. Furthermore, the free running mode in a modern sCMOS camera helps to achieve faster data acquisition.

Abstract:We describe a two-beam interference structured illumination fluorescence microscope. The novelty of the presented system lies in its simplicity. A programmable electro-optical spatial light modulator in an intermediate image plane enables precise and rapid control of the excitation pattern in the specimen. The contrast of the projected light pattern is strongly influenced by the polarization state of the light entering the high NA objective. To achieve high contrast, we use a segmented polarizer. Furthermore, a mask with six holes blocks unwanted components in the spatial frequency spectrum of the illumination grating. Both these passive components serve their purpose in a simpler and almost as efficient way as active components. We demonstrate a lateral resolution of 114.2 ± 9.5 nm at a frame rate of 7.6 fps per reconstructed 2D slice.

High optical resolution in microscopy usually goes along with costly hardware components, such as lenses, mechanical setups and cameras. Several studies proved that Single Molecular Localization Microscopy can be made affordable, relying on off-the-shelf optical components and industry grade CMOS cameras. Recent technological advantages have yielded consumer-grade camera devices with surprisingly good performance. The camera sensors of smartphones have benefited of this development. Combined with computing power smartphones provide a fantastic opportunity for “imaging on a budget”. Here we show that a consumer cellphone is capable of optical super-resolution imaging by (direct) Stochastic Optical Reconstruction Microscopy (dSTORM), achieving optical resolution better than 80 nm. In addition to the use of standard reconstruction algorithms, we used a trained image-to-image generative adversarial network (GAN) to reconstruct video sequences under conditions where traditional algorithms provide sub-optimal localization performance directly on the smartphone. We believe that “cellSTORM” paves the way to make super-resolution microscopy not only affordable but available due to the ubiquity of cellphone cameras.

Tracking and analyzing the individual diffusion of nanoscale objects such as proteins and viruses is an important methodology in life science. Here, we show a sensor that combines the efficiency of light line illumination with the advantages of fluidic confinement. Tracking of freely diffusing nano-objects inside water-filled hollow core fibers with core diameters of tens of micrometers using elastically scattered light from the core mode allows retrieving information about the Brownian motion and the size of each particle of the investigated ensemble individually using standard tracking algorithms and the mean squared displacement analysis. Specifically, we successfully measure the diameter of every gold nanosphere in an ensemble that consists of several hundreds of 40 nm particles, with an individual precision below 17% (±8 nm). In addition, we confirm the relevance of our approach with respect to bioanalytics by analyzing 70 nm λ-phages. Overall these features, together with the strongly reduced demand for memory space, principally allows us to record thousands of frames and to achieve high frame rates for high precision tracking of nanoscale objects.

Spatial light modulators (SLM) update in a synchronous manner, whereas the data readout process in fast structured illumination systems is usually done using a rolling shutter camera with asynchronous readout. In structured illumination microscopy (SIM), this leads to synchronization problems causing a speed limit for fast acquisition. In this paper we present a configuration to overcome this limit by exploiting the extremely fast SLM display and dividing it into several segments along the direction of the rolling shutter of the sCMOS camera and displaying multiple SLM frames per camera acquisition. The sCMOS runs in continuous rolling shutter mode and the SLM keeps the readout-line always inside a dark region presenting different SIM patterns before and after the readout/start-exposure line. Using this approach, we reached a raw frame rate of 714 frames per second (fps) resulting in a two-beam SIM acquisition rate of 79 fps with a region of interest (ROI) of 16.5  ×  16.5 μm2.

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Fiber-based 3D tracking of nano-scale objects with high spatiotemporal resolution is demonstrated for exploring dynamics at the nanoscale levels.