Optical nanoscopy is crucial in life and materials sciences, revealing subtle cellular processes and nanomaterial properties. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) provides nanoscale resolution, relying on the interactions taking place between a laser beam, a sharp tip and the sample. The Atomic Force Microscope (AFM) is a fundamental part of an s-SNOM system, providing the necessary probe-sample feedback mechanisms for data acquisition. In this Letter, we demonstrate that s-SNOM data can be partially inferred from AFM images. We first show that a generative artificial intelligence (AI) model (pix2pix) can generate synthetic s-SNOM data from experimental AFM images. Second, we demonstrate that virtual s-SNOM data can be extrapolated from knowledge of the tip position and, consequently, from AFM signals. To this end, we introduce an analytical model that explains the mechanisms underlying AFM-to-s-SNOM image translation. These insights have the potential to be integrated into future physics-informed explainable AI models. The two proposed approaches generate pseudo s-SNOM data without direct optical measurements, significantly expanding access to optical nanoscopy through widely available AFM systems. This advancement holds great promise for reducing both time and costs associated with nanoscale imaging.

The global mortality rate from antimicrobial-resistant infections is steadily rising, driven primarily by the widespread use of antibiotics in the last decades, a problem exacerbated during the COVID-19 pandemic. The exponential growth of antimicrobial resistance far outpaces the current development of new antibiotics. One promising strategy to counteract the rise of antibiotic-resistant bacteria is the use of nanomaterials as antimicrobial agents. In recent works, Zinc-Doped Iron Oxide ZnxFe3-xO4 nanoparticles (NPs) have been demonstrated as a highly efficient cancer theranostics agent capable of several different, complementary, therapeutic routes, depending on the Zn doping concentration. In this study, we demonstrate for the first time the interesting antibacterial effects of this nanomaterial, investigating the interactions of ZnxFe3-xO4 NPs with various Zn concentrations (0.2 %, 1 %, 1.5 %, 2 %) with two opportunistic pathogens: the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Pseudomonas aeruginosa, both of which are among the top resistant nosocomial pathogens, and model organisms. We adopt a holistic approach, looking at: (i) the antimicrobial effects of ZnxFe3-xO4 NPs, either alone, or in combination with two antibiotics, gentamicin (CN) and ciprofloxacin (CIP), (ii) their efficacy at dispersing bacterial planktonic aggregates, and (iii) their inhibitory properties of biofilm formation. Last, we employ Atomic Force Microscopy (AFM) for qualitative and quantitative analyses of bacterial cells treated with CIP, CN, and ZnxFe3-xO4 NPs to enable knowledge of the mechanisms of antibacterial action of the latter.

Enhancing spectral resolution in a conventional arrayed waveguide grating AWG requires a longer differential optical path, which expands the device footprint and increases sensitivity to phase noise. To overcome this limitation, we propose an innovative approach that maintains the AWG layout and introduces an additional splitter at the device input. Leveraging the Moiré effect, generated by two gratings with slightly different pitches, we demonstrate that the spacing of a 7 channel multiplexer/demultiplexer can be reduced to 1 GHz at the central wavelength of 1550 nm. We present the theoretical foundation for a super-resolution AWG and provide the corresponding design guidelines.

We propose a novel all-optical hybrid MDM-OFDM system that enables variable transmission capacity by seamlessly switching between two-mode full subcarriers and single-mode sparse subcarriers multiplexing through the use of power loading. The operation depends on the mode crosstalk present between the arrayed waveguide grating and the two-mode fiber. Through rigorous analysis, our results indicate that for the two-mode full subcarrier multiplexing, a power loading of 0.78 dB for the TE10 mode guarantees uniform performance across all subcarriers. Furthermore, by effectively suppressing the TE10 mode using a power loading of 12 dB, our system achieves similar performances and functionality to single-mode sparse subcarrier multiplexing, wherein only the TE00 mode is utilized. Our system offers variable transmission rates for data center connections, using all-optical signal processing, without varying the modulation scheme and the symbol rate.

We propose a novel arrayed waveguide grating layout to achieve spectral resolution below 1 GHz at telecom wavelengths. We describe the working principle based on the Moire effect and provide design guidelines for a high-resolution planar multiplexer/demultiplexer.

We present three novel joint detection receiver configurations that can be fabricated using planar lightwave circuit technology and evaluate their performance in quantum communication systems. By leveraging Hadamard, Fourier, and fractional Fourier codewords, these architectures enhance system capacity, while improving power efficiency.

Optical links can achieve spectral efficiencies beyond the Shannon limit by employing quantum joint detection receivers that decode messages collectively. We introduce a novel quantum-enhanced optical system based on Fourier codewords, that are generated and processed by a single arrayed waveguide grating. Numerical comparisons between the Fourier machine and the conventional Green machine demonstrate a quantum advantage in the low photon-number regime for both. Additionally, we propose a parallel configuration of the Fourier machine and numerically investigate its spectral efficiency

Superadditive quantum communication uses joint detection receivers to boost the system capacity. We explore the theoretical foundations and challenges of integrating quantum technologies into existing optical networks, evaluating their performance in a noisy channel.

A two-mode optical packet switching architecture using an optical multiport mode-division multiplexing label generator and processor is proposed. By combining optical labels on two modes, the number of labels is increased exponentially. Beat noise significantly affects the label error rate, when multimode crosstalk is maximum. This impairment can be mitigated by time shifting the optical labels of the two modes by half of the label duration.

We outline design guidelines for AWGs, highlighting their versatility beyond conventional MUX/DeMUX functionality. We describe AWG configurations for time-frequency packing, optical Fourier transform and fractional Fourier transforms, as well as for enhanced filter shaping, offering improved bandwidth performance.

Infectious diseases are acknowledged as one of the leading causes of death worldwide. Statistics show that the annual death toll caused by bacterial infections has reached 14 million, most of which are caused by drug-resistant strains. Bacterial antibiotic resistance is currently regarded as a compelling problem with dire consequences, which motivates the urgent identification of alternative ways of fighting bacteria. Various types of nanomaterials have been reported to date as efficient antibacterial solutions. Among these, carbon-based nanomaterials, such as carbon nanodots, carbon graphene oxide, and carbon nanotubes (CNTs), have been shown to be effective in killing a wide panel of pathogenic bacteria. With this study, we aim to provide additional insights into this topic of research by investigating the antibacterial activity of a specific type of multiwalled CNTs, with diameters from 50 to 150 nm, against two representative opportunistic pathogens, i.e., the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Pseudomonas aeruginosa, both included among the top antibiotic-resistant pathogens. We also test the synergistic effect of CNTs with different antibiotics commonly used in the treatment of infections caused by S. aureus and/or P. aeruginosa. Additionally, a novel approach for quantitatively analyzing bacterial aggregation in brightfield microscopy images was implemented. This method was utilized to assess the effectiveness of CNTs, either alone or in combination with antibiotics, in dispersing bacterial aggregates. Finally, atomic force microscopy coupled with a newly devised image analysis pipeline was used to examine any potential morphological changes in bacterial cells following exposure to CNTs and antibiotics.

The ability to exchange messages between distant users is the cornerstone of the second industrial revolution and a crucial stepping stone of the current third industrial revolution, involving digital technologies and automation. As the bit rate approaches the nonlinear channel capacity, it is necessary to provide quantum-mechanical description of the information transmission and processing. We review the modeling approach of information carriers as quantum-optical states, assessing the advantages of considering the Holevo capacity compared to the Shannon capacity. We present a novel quantum-limited all-optical architecture based on Fourier codes generated by a single passive multiport encoder/decoder. We demonstrate that the proposed Fourier machine presents a coding efficiency larger than Shannon limit.

In the past years, optical fluorescence microscopy (OFM) made steady progress towards increasing the localisation precision of fluorescent emitters in biological samples. The high precision achieved by these techniques has prompted new claims, whose rigorous validation is an outstanding problem. For this purpose, local estimation theory (LET) has emerged as the most used mathematical tool. We establish a novel multi-parameter estimation framework that captures the full complexity of single-emitter localisation in an OFM experiment. Our framework relies on the fact that there are other unknown parameters alongside the emitter's coordinates, such as the average number of photons emitted (brightness), that are correlated to the emitter position, and affect the localisation precision. The increasing complexity of a multi-parameter approach allows for a more accountable assessment of the precision. We showcase our method with MINFLUX microscopy, the OFM approach that nowadays generates images with the best resolution. Introducing the brightness as an unknown parameter, we shed light on features that remain obscure in the conventional approach: the precision can be increased only by increasing the brightness, (i.e., illumination power or exposition time), whereas decreasing the beam separation offers limited advantages. We demonstrate that the proposed framework is a solid and general method for the quantification of single-emitter localisation precision for any OFM approach on equal footing, evaluating the localization precision of stimulated emission depletion (STED) microscopy and making a comparison with MINFLUX microscopy.

A single-mode labeling approach is proposed for a mode- multiplexed OPS system, and the corresponding detection performances are evaluated as a function of the received power. We introduce the mode dimension to increase the number of labels that can be generated and processed by a single multiport E/D, and we analyze configurations with reduced intra-mode crosstalk. We show that the label error rate is significantly influenced by inter-mode crosstalk, being TE10 labels more susceptible to crosstalk from adjacent ports, than TE00 labels.

An arrayed waveguide grating (AWG) configuration can simultaneously perform the optical discrete Fourier transform and multiplex and demultiplex (MUX/DeMUX) two optical modes, to optically generate/process orthogonal frequency division multiplexing (OFDM) signals in future scalable, converged two-mode optical communication systems. We use a single AWG-based MUX/DeMUX, inter-mode and intra-optical-subcarrier symbol interleaving to mitigate the mode/subcarrier crosstalk. We analyze the performance of a 2-mode x 8 optical-subcarrier x 10 Gbit/s, on-off keying (OOK), differential phase shift keying (DPSK), and differential quadrature phase shift keying (DQPSK) mode division multiplexing (MDM)-OFDM system, that can be used in high-speed, large-capacity short-range optical link, using only passive all-optical signal processing. We numerically demonstrate that it possible to achieve error-free transmission for an 8 subcarrier x 10 Gbit/s x 2 mode system, using OOK and DPSK modulation and for a 4 subcarrier x 10 Gbit/s x 2 mode system, using DQPSK modulation, using intra-optical-subcarrier symbol interleaving.

ABSTRACT Our understanding of bacteria is increasingly dependent on our ability to visualize cellular processes at the single-cell level with high spatial and temporal resolution. Advances in fluorescence microscopy are accompanied by an increasing demand for novel fluorophores that enable tagging specific bacterial components. In this context, new fluorescent probes emitting in the far-red (FR) are of particular interest as they reduce possible interference caused by sample autofluorescence and increase flexibility in multicolor imaging experiments. In this study, an extended set of previously reported and newly synthesized FR-emitting dyes has been characterized for their applicability in live single-cell imaging of the Gram-negative and Gram-positive prototype bacteria Escherichia coli and Bacillus subtilis. Toxicity tests demonstrated that these dyes do not interfere with the growth kinetics of both species, opening up the possibility of using them in live-cell imaging. Moreover, confocal laser-scanning microscopy imaging revealed that all the tested dyes can distinguish viable from dead bacterial cells. Among the newly synthesized fluorophores, the oxazine derivative KK 1905-NHS was particularly efficient in membrane staining and was effectively employed to monitor membrane biogenesis using a two-step labeling protocol on living cells. In addition, KK 1905-NHS was successfully used in super-resolution stimulated emission depletion microscopy. Overall, the new fluorophores presented in this study expand the microscopy toolbox, which is an asset for the investigation of fundamental bacterial processes. IMPORTANCE By harnessing the versatility of fluorescence microscopy and super-resolution imaging, bacteriologists explore critical aspects of bacterial physiology and resolve bacterial structures sized beyond the light diffraction limit. These techniques are based on fluorophores with profitable photochemical and tagging properties. The paucity of available far-red (FR)-emitting dyes for bacterial imaging strongly limits the multicolor choice of bacteriologists, hindering the possibility of labeling multiple structures in a single experiment. The set of FR fluorophores characterized in this study expands the palette of dyes useful for microbiologists, as they can be used for bacterial LIVE/DEAD staining and for tagging the membranes of viable Escherichia coli and Bacillus subtilis cells. The absence of toxicity makes these dyes suitable for live-cell imaging and allows monitoring of bacterial membrane biogenesis. Moreover, a newly synthesized FR-fluorophore can be employed for imaging bacterial membranes with stimulated emission depletion microscopy, a super-resolution technique capable of increasing the resolving power of conventional microscopes.

We review different super-resolution microscopy approaches used by microbiologists to investigate bacterial cell morphology and functions. We evidence the resolution achieved and focus on fluorophore selection and other critical imaging requirements. Some recent applications are described, which have defined novel insights into bacterial cellular structures. In particular, we evidenced the pivotal role that super-resolution microscopy can play in a near future to deal with antimicrobial resistance.

We numerically show the subcarrier performance uniformity in an all-optical hybrid mode division multiplexing and orthogonal frequency division multiplexing (MDM-OFDM) system with inter-mode sparse subcarrier multiplexing and inter-optical-subcarrier symbol interleaving, using an inter-mode subcarrier group power loading.