arXiv subjects

Artur Bednarkiewicz

Publications and source records attributed to Artur Bednarkiewicz.

5 recordsLinked to original sources

arXiv2026

Non-invasive super-resolution imaging through scattering media using highly nonlinear labels

While scattered light conveys most of the information we perceive, scattering may also distort that information before it reaches our detectors. The problem is acute in many applications, such as in high-resolution microscopy of biological tissue, where scattering degrades both resolution and signal-to-noise ratio. Here, for the first time, we demonstrate that combining two intrinsic properties of scattered light: speckle statistics and the memory effect, with highly non-linear optical response yields, rather surprisingly, super-resolution, low-background, non-invasive imaging of objects completely hidden behind a strongly scattering, opaque layers. Crucially, our technique of Nonlinear Imaging with Speckle Excitation (NISE) does not resort to wavefront shaping, adaptive optics, complicated optical setups, or iterative image reconstruction algorithms. Because the strategy relies solely on the properties of scattered light and high-order nonlinear response of the luminescent labels, it can be applied to any speckle-forming propagation, from biological tissue to multicore fibers, combined with any type of phenomenon that exhibits a sufficiently high order nonlinearity.

physics.optics↗

arXiv2025

Label free sub-diffraction imaging using non-linear photon avalanche backlight

Optical imaging below the limit of light diffraction offers an unprecedented opportunity to study outlook, organization, interactions or in-situ functioning of sub-micrometer, highly transparent objects such as subcellular structures in vitro, thin layers or nano-engineered devices. However, most of current methodologies require to use specially designed luminescent labels, which not only may affect the properties of the sample itself, but often are (photo)toxic, susceptible to photobleaching, offer limited color combinations or specificity of labeling. Moreover, the dedicated fluorescence based super-resolution optical techniques are often technically complex and cumbersome to use. The existing non-destructive, non-invasive and label-free super-resolution imaging (SRI) methods are also challenging, complex and elusive to apply. To address these issues, here we propose and experimentally demonstrate a new concept of label-free sub-diffraction optical imaging. The transmission avalanche backlight (TAB) microscopy exploits huge optical non-linearities of photon avalanching materials, which are acting as a virtual near-field nano aperture - a diffraction limited backlight of the actual sample. Such approach enables to augment imaging contrast of highly transparent samples and thin layers, by translating small attenuation and scattering loses occurring on these translucent samples into amplified modulation of luminescence intensity of the avalanche backlighted substrate (ABS). At no additional cost, sub-diffraction imaging is achieved with simple, single beam laser scanning microscopy setup, leading to ca. 70 nm optical resolution. This far-field, label-free, raster scanning imaging technique, with augmented contrast and optical imaging resolution below diffraction limit, may become pivotal for studies in biology, physics, materials science, nanophotonics and nanoengineering

physics.optics↗

arXiv2024

The mechanisms behind extreme susceptibility of photon avalanche emission to quenching

The photon avalanche (PA) process that emerges in lanthanide-doped crystals yields a threshold and highly nonlinear (of the power law order > 5) optical response to photoexcitation. PA emission is the outcome of excited-state absorption combined with a cross-relaxation process, which creates positive and efficient energy looping. In consequence, this combination of processes should be highly susceptible to small perturbations in energy distribution and thus can be hindered by other competitive 'parasite' processes such as energy transfer (ET) to quenching sites. Although luminescence quenching is a well-known phenomenon, the exact mechanisms of susceptibility of PA to resonant energy transfer (RET) remain poorly understood limiting practical applications. A deeper understanding of these mechanisms may pave the way to new areas of PA exploitation. This study focuses on the investigation of the LiYF$_{4}$:3%Tm$^{3+}$ PA system co-doped with $Nd^{3+}$ acceptor ions, which was found to impact both the looping and emitting levels and thus to effectively disrupt PA emission, causing an increase in the PA threshold ($I_{th}$) and a decrease in PA nonlinearity ($S_{max}$). Our complementary modelling results revealed that the ET from the looping level increased $I_{th}$ and $S_{max}$, whereas the ET from the emitting level diminished $S_{max}$ and the final emission intensity. Ultimately, significant PA emission quenching demonstrates a high relative sensitivity ($S_{R}$) to infinitesimal amounts of $Nd^{3+}$ acceptors, highlighting the potential for PA to be utilized as an ultra-sensitive, fluorescence-based reporting mechanism that is suitable for the detection and quantification of physical and biological phenomena or reactions.

cond-mat.mtrl-sci↗

arXiv2021

Phase transition facilitated highly sensitive luminescence nanothermometry and thermal imaging

Currently available temperature measurements or imaging at nano-micro scale are limited to fluorescent molecules and luminescent nanocrystals, whose spectral properties respond to temperature variation. The principle of operation of these conventional temperature probes is typically related to temperature induced multiphonon quenching or temperature dependent energy transfers, therefore, above 12%/K sensitivity and high thermal resolution remain a serious challenge. Here we demonstrate a novel class of highly sensitive thermographic phosphors operating in room temperature range with milikelvin thermal resolution, whose temperature readings are reproducible, luminescence is photostable and brightness is not compromised by thermal quenching. Corroborated with phase transition structural characterization and high spatio-temporal temperature imaging, we demonstrated that optically active europium ions are highly and smoothly susceptible to monoclinic to tetragonal phase transition in LiYO2 host, which is evidenced by changed number and the splitting of Stark components as well as by smooth variation of contribution between magnetic and electric dipole transitions. Further, reducing the size of phosphor from bulk to nanocrystalline matrix, shifted the phase transition temperature from 100oC down to room temperature. These findings provide insights into the mechanism underlaying phase transition based luminescence nanothermometry and motivate future research toward new, highly sensitive, high temporal and spatial resolution nano-thermometers aiming at precise studying heat generation or diffusion in numerous biological and technology applications.

cond-mat.mtrl-sci↗

arXiv2020

Giant nonlinear optical responses from photon avalanching nanoparticles

Avalanche phenomena leverage steeply nonlinear dynamics to generate disproportionately high responses from small perturbations and are found in a multitude of events and materials, enabling technologies including optical phase-conjugate imaging, infrared quantum counting, and efficient upconverted lasing. However, the photon avalanching (PA) mechanism underlying these optical innovations has been observed only in bulk materials and aggregates, and typically at cryogenic temperatures, limiting its utility and impact. Here, we report the realization of PA at room temperature in single nanostructures--small, Tm-doped upconverting nanocrystals--and demonstrate their use in superresolution imaging at near-infrared (NIR) wavelengths within spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave or pulsed lasers and exhibit all of the defining features of PA. These hallmarks include excitation power thresholds, long rise time at threshold, and a dominant excited-state absorption that is >13,000x larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of pump intensity. This enables the realization of photon-avalanche single-beam superresolution imaging (PASSI), achieving sub-70 nm spatial resolution using only simple scanning confocal microscopy and before any computational analysis. Pairing their steep nonlinearity with existing superresolution techniques and computational methods, ANPs allow for imaging with higher resolution and at ca. 100-fold lower excitation intensities than is possible with other probes. The low PA threshold and exceptional photostability of ANPs also suggest their utility in a diverse array of applications including sub-wavelength bioimaging, IR detection, temperature and pressure transduction, neuromorphic computing, and quantum optics.

physics.optics↗