Chip-based label-free incoherent super-resolution optical microscopy.

The photo-kinetics of fluorescent molecules have enabled the circumvention of the 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.

From superior contrast to super resolution label free optical microscopy.

Label-free optical microscopy utilizes the information encoded in light scattered off unlabeled particles to generate the images. This review article starts off with a discussion on how this light matter interaction gives rise to the issues of poor-contrast and diffraction-limited spatial resolution. Then, this article reviews the various far-field label-free optical microscopy techniques that have been developed, with an emphasis on the physical mechanisms behind the image formation processes in such techniques.

Low-loss, low-background aluminum oxide waveguide platform for broad-spectrum on-chip microscopy.

A versatile wide-spectrum photonic integrated circuit (PIC) platform, spanning from ultraviolet (UV) to infrared (IR) wavelengths, is essential for advancing on-chip optical microscopy and spectroscopy applications. The key desirable requirements for PICs are low-loss, low-autofluorescence background signals, and high-refractive index contrast (HIC) to enable compact designs. Here, we present a low-loss, low-autofluorescence aluminum oxide (AlO) waveguide platform developed using atomic layer deposition (ALD).

Erratum to: Multi-moded high-index contrast optical waveguide for super-contrast high-resolution label-free microscopy.

[This corrects the article DOI: 10.1515/nanoph-2022-0100.].

Demystifying speckle field interference microscopy.

Dynamic speckle illumination (DSI) has recently attracted strong attention in the field of biomedical imaging as it pushes the limits of interference microscopy (IM) in terms of phase sensitivity, and spatial and temporal resolution compared to conventional light source illumination. To date, despite conspicuous advantages, it has not been extensively implemented in the field of phase imaging due to inadequate understanding of interference fringe formation, which is challenging to obtain in dynamic speckle illumination interference microscopy (DSI-IM). The present article provides the basic understanding of DSI through both simulation and experiments that is essential to build interference microscopy systems such as quantitative phase microscopy, digital holographic microscopy and optical coherence tomography.

Multi-moded high-index contrast optical waveguide for super-contrast high-resolution label-free microscopy.

The article elucidates the physical mechanism behind the generation of superior-contrast and high-resolution label-free images using an optical waveguide. Imaging is realized by employing a high index contrast multi-moded waveguide as a partially coherent light source. The modes provide near-field illumination of unlabeled samples, thereby repositioning the higher spatial frequencies of the sample into the far-field.

High-throughput spatial sensitive quantitative phase microscopy using low spatial and high temporal coherent illumination.

High space-bandwidth product with high spatial phase sensitivity is indispensable for a single-shot quantitative phase microscopy (QPM) system. It opens avenue for widespread applications of QPM in the field of biomedical imaging. Temporally low coherence light sources are implemented to achieve high spatial phase sensitivity in QPM at the cost of either reduced temporal resolution or smaller field of view (FOV).

Characterization of Liposomes Using Quantitative Phase Microscopy (QPM).

The rapid development of nanomedicine and drug delivery systems calls for new and effective characterization techniques that can accurately characterize both the properties and the behavior of nanosystems. Standard methods such as dynamic light scattering (DLS) and fluorescent-based assays present challenges in terms of system's instability, machine sensitivity, and loss of tracking ability, among others. In this study, we explore some of the downsides of batch-mode analyses and fluorescent labeling, while introducing quantitative phase microscopy (QPM) as a label-free complimentary characterization technique.

On-chip TIRF nanoscopy by applying Haar wavelet kernel analysis on intensity fluctuations induced by chip illumination.

Photonic-chip based TIRF illumination has been used to demonstrate several on-chip optical nanoscopy methods. The sample is illuminated by the evanescent field generated by the electromagnetic wave modes guided inside the optical waveguide. In addition to the photokinetics of the fluorophores, the waveguide modes can be further exploited for introducing controlled intensity fluctuations for exploitation by techniques such as super-resolution optical fluctuation imaging (SOFI).

Sampling moiré method: a tool for sensing quadratic phase distortion and its correction for accurate quantitative phase microscopy.

The advantages of quantitative phase microscopy (QPM) such as label-free imaging with high spatial sensitivity, live cell compatibility and high-speed imaging makes it viable for various biological applications. The measurement accuracy of QPM strongly relies on the shape of the recorded interferograms, whether straight or curved fringes are recorded during the data acquisition. Moreover, for a single shot phase recovery high fringe density is required.

Polarization evolution in single-ring antiresonant hollow-core fibers.

Understanding polarization in waveguides is of fundamental importance for any photonic device and is particularly relevant within the scope of fiber optics. Here, we investigate the dependence of the geometry-induced polarization behavior of single-ring antiresonant hollow-core fibers on various parameters from the experimental perspective, showing that structural deviations from an ideal polygonal shape impose birefringence and polarization-dependent loss, confirmed by a toy model. The minimal output ellipticity was found at the wavelength of lowest loss near the center of the transmission band, whereas birefringence substantially increases toward the resonances.