Fundamental precision limits of fluorescence microscopy: a perspective on MINFLUX.

Over the past years, fluorescence microscopy (FM) has steadily progressed in increasing the localization precision of fluorescent emitters in biological samples and led to new claims, whose rigorous validation remains an outstanding problem. We present a novel, to the best of our knowledge, multi-parameter estimation framework that captures the full complexity of a single-emitter FM localization experiment. We showcase our method with Minimum Flux (MINFLUX) microscopy, among the highest-resolution approaches, demonstrating that (i) the localization precision can be increased only by turning the illumination intensity up, thus increasing the risk of photo-bleaching, and it is independent from the beams' separation, and (ii) in presence of background noise, the localization precision decreases with the beams' separation.

Antibacterial Interactions of Ethanol-Dispersed Multiwalled Carbon Nanotubes with and .

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.

Expanding the microbiologist toolbox new far-red-emitting dyes suitable for bacterial imaging.

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.

An image processing-based quantification of gram variability in Acinetobacter baumannii.

Gram staining differentiates bacteria as gram-positive and gram-negative, depending on their cell wall constituents, and coloring cells in violet and pink, respectively. Sometimes, a subpopulation of the same bacterial species assumes different colors, ranging from pink to violet, for reasons that are not completely understood yet. We analyze conventional brightfield images and use an automated pipeline to count pink and violet cells.

Growth Phase- and Desiccation-Dependent Morphology: An Atomic Force Microscopy Investigation.

has emerged as a major bacterial pathogen during the past three decades. The majority of the infections occur in hospitals and are caused by strains endowed with high desiccation tolerance, which represents an essential feature for the adaptation to the nosocomial environment. This work aims at investigating the desiccation response of the multidrug-resistant strain ACICU as a function of the bacterial growth phase and oxygen availability, by correlating bacterial survival with shape alterations.

SSNOMBACTER: A collection of scattering-type scanning near-field optical microscopy and atomic force microscopy images of bacterial cells.

Background: In recent years, a variety of imaging techniques operating at nanoscale resolution have been reported. These techniques have the potential to enrich our understanding of bacterial species relevant to human health, such as antibiotic-resistant pathogens. However, owing to the novelty of these techniques, their use is still confined to addressing very particular applications, and their availability is limited owing to associated costs and required expertise.

STED nanoscopy of KK114-stained pathogenic bacteria.

Super-resolution microscopy techniques can provide answers to still pending questions on prokaryotic organisms but are yet to be used at their full potential for this purpose. To address this, we evaluate the ability of the rhodamine-like KK114 dye to label various types of bacteria, to enable imaging of fine structural details with stimulated emission depletion microscopy (STED). We assessed fluorescent labeling with KK114 for eleven Gram-positive and Gram-negative bacterial species and observed that this contrast agent binds to their cell membranes.

Geometrical-optics approach to measure the optical density of bacterial cultures using a LED-based photometer.

We develop a suitable geometrical-optics approach and demonstrate that it is possible to measure the optical density (OD) of bacterial cultures using a light emitting diode (LED)-based photometer. We measure both attenuation and spot-size variation, and we compensate for diffraction and stray-light impairment related to the incoherent source and large detection area. The approach is validated for different concentrations of two bacterial species, and , that present different shapes and clustering organization.

Geometrical-optics approach to increase the accuracy in LED-based photometers for point-of-care testing.

A geometrical-optics approach is proposed to increase the accuracy in photometric measurements, using a point-of-care testing (POCT) LED-based sensor. Due to stray-light effects, the measurement accuracy depends on the dimension of the CMOS area, where the radiation is detected. We propose two image processing approaches and evaluate the influence of the sensor area.

New Shuttle Vectors for Real-Time Gene Expression Analysis in Multidrug-Resistant Acinetobacter Species: and Responses to Environmental Stressors.

The genus includes species of opportunistic pathogens and harmless saprophytes. The type species, , is a nosocomial pathogen renowned for being multidrug resistant (MDR). Despite the clinical relevance of infections caused by MDR and a few other spp.

Demonstration of PAM4-OCDM system with electrical amplitude-level pre-tuning and post-equalization for data centers applications.

A PAM4-OCDM system with optical multi-/demultiplexing and electrical pre-/post-processing is proposed for short-reach applications. We experimentally demonstrate, for the first time, a power-efficient 4 OC x 10 GSymbol/s PAM4-OCDM system. The four PSK-OCs are simultaneously generated using a single light source and a passive multiport optical encoder and received by a single optical decoder and cascaded DSP.

All-optical Nyquist-OTDM to Nyquist-WDM conversion for high-granular flexible optical networks.

We have proposed and experimentally demonstrated all-optical multiplexing (MUX)-format conversion from Nyquist optical time division multiplex (OTDM) to Nyquist wavelength division multiplex (WDM). The system is simply configured with a straight-type phase modulator (PM) driven by a sinusoidal wave and an optical Nyquist filter. In the theoretical investigation, it is proved that the single Nyquist signal is completely converted to Nyquist WDM signal, which consists of two half-baud-rate signals with different carrier frequencies.

A low-power photonic quantization approach using OFDM subcarrier spectral shifts.

Photonic analog-to-digital conversion and optical quantization are demonstrated, based on the spectral shifts of orthogonal frequency division multiplexing subcarriers and a frequency-packed arrayed waveguide grating. The system is extremely low-energy consuming since the spectral shifts are small and generated by cross-phase modulation, using a linear-slope high-speed and low-jitter pulse train generated by a mode locked laser diode. The feasibility of a 2, 3 and 4-bit optical quantization scheme is demonstrated.

First demonstration of a scalable MDM/CDM optical access system.

A novel hybrid all-optical mode-division multiplexing and code division multiplexing architecture for flexible and scalable access networks is presented. We successfully demonstrate, for the first time, an asynchronous on-off keying modulation, 2 mode x 4 code x 10 Gbps transmission over 42-km link, using a set of single-mode and two-mode fibers, without dispersion compensation. The four phase-shift keyed optical codes are generated at a single wavelength, by a multiport encoder/decoder, and we use an optical mode multiplexer/demultiplexer in the remote node and at the central office.

Chromatic dispersion monitoring and adaptive compensation using pilot symbols in an 8 x 12.5 Gbit/s all-optical OFDM system.

We propose and experimentally demonstrate a novel technique for chromatic dispersion (CD) monitoring and adaptive compensation in an 8 x 12.5 Gbit/s all-optical orthogonal frequency-division multiplexing (AO-OFDM) system by using two pilot symbols and a virtually imaged phased array (VIPA) for a tunable CD compensator. The two pilot symbols are added to the first and the last sub-channels of the OFDM signal, and their relative time delay is detected and used for CD estimation at the CD monitoring circuit.

Tunable optical code converter using XPM and linear-slope pulse streams generated by FBGs.

We propose for the first time (to the best of our knowledge) and demonstrate a tunable multiple optical code (OC) converter for flexible networks that allows dynamic code (bandwidth) allocation in a way similar to a tunable laser. With respect to other OC converters, this scheme can convert both specific and multiple OCs by changing only the amplifier gain. The proposed scheme uses cross-phase modulation (XPM) and two linear-slope control pulse streams generated by fiber Bragg gratings (FBGs) in the C-band.

Demonstration and performance investigation of all-optical OFDM systems based on arrayed waveguide gratings.

We experimentally demonstrate an 8 x 12.5 Gbit/s all-optical orthogonal frequency-division multiplexing (AO-OFDM) system using arrayed waveguide gratings (AWGs), which perform discrete Fourier transform (DFT) and inverse DFT (IDFT) of a signal directly in the optical domain. The experimental results show that frequency orthogonality of OFDM sub-channels is degraded in the AWG due to the slab-diffraction effect.

What else can an AWG do?

The present paper aims to describe other functionalities for an arrayed waveguide grating (AWG)-based device, showing that this widely used configuration can be designed not only to frequency multiplex/demultiplex wavelength division multiplexing (WDM) signals, but also to perform the discrete Fourier transform (DFT) and the discrete fractional Fourier transform (DFrFT) of a signal, in all-optical orthogonal frequency division multiplexing (OFDM) systems. In addition 1 × N and N × N phased array switches architectures are described, as well as a new configuration to perform polarization diversity demultiplexing. Finally, a general approach, based on an analogy with the finite impulse response (FIR) filter approach, is presented to design optical modulators for any modulation format, using either phase modulators (PM) or electro-absorption modulators (EAM).

Noise suppression using optimum filtering of OCs generated by a multiport encoder/decoder.

We propose a novel receiver configuration using an extreme narrow band-optical band pass filter (ENB-OBPF) to reduce the multiple access interference (MAI) and beat noises in an optical code division multiplexing (OCDM) transmission. We numerically and experimentally demonstrate an enhancement of the code detectability, that allows us to increase the number of users in a passive optical network (PON) from 4 to 8 without any forward error correction (FEC).

Demonstration of asynchronous, 40 Gbps x 4-user DPSK-OCDMA transmission using a multi-port encoder/decoder.

We have developed a new 8-chip, 320 Gchip/s encoder/decoder with eight input/output ports, that can be used in 40-Gb/s PON networks. The device has been to multiplex four asynchronous 40 Gb/s users, using DPSK modulation. The transmission over 50 km has been successfully demonstrated for the first time.

Generalized fiber Fourier optics.

A twofold generalization of the optical schemes that perform the discrete Fourier transform (DFT) is given: new passive planar architectures are presented where the 2 × 2 3 dB couplers are replaced by M × M hybrids, reducing the number of required connections and phase shifters. Furthermore, the planar implementation of the discrete fractional Fourier transform (DFrFT) is also described, with a waveguide grating router (WGR) configuration and a properly modified slab coupler.

High-security 2.5 Gbps, polarization multiplexed 256-ary OCDM using a single multi-port encoder/decoder.

A block-ciphered (M-ary) optical code division multiplexing (OCDM) can provide larger security than a conventional OCDM system based on bit ciphering. We propose a polarization multiplexed (POL-MUX) M-ary OCDM system and demonstrated 2.5 Gbps, POL-MUX 256 ( = 16X16)-ary OCDM transmission using a single multi-port optical encoder/decoder (E/D).

Spectral coherent-state quantum cryptography.

A novel implementation of quantum-noise optical cryptography is proposed, which is based on a simplified architecture that allows long-haul, high-speed transmission in a fiber optical network. By using a single multiport encoder/decoder and 16 phase shifters, this new approach can provide the same confidentiality as other implementations of Yuen's encryption protocol, which use a larger number of phase or polarization coherent states. Data confidentiality and error probability for authorized and unauthorized receivers are carefully analyzed.

Field trial of 160 Gbit/s DWDM-based optical packet switching and transmission.

We demonstrated, for the first time, a field trial of 160 (16 lambda x 10) Gbit/s, fine granularity, DWDM-based optical packet switching and transmission by newly-developed burst-mode EDFAs and an optical packet switch prototype with multiple all-optical label processors. We achieved 64 km field transmission and switching of 160 (16 lambda x 10) Gbit/s DWDM-based optical packets encapsulating almost 10 Gbit/s IP packets with error-free operation (IP-packet-loss-rate <10(-6) and bit-error-rate <10(-9)).

Angular momentum dynamics of a paraxial beam in a uniaxial crystal.

The conservation law governing the dynamics of the radiation angular momentum component along the optical axis (z axis) of a uniaxial crystal is derived from Maxwell's equations; the existence of this law is physically related to the rotational invariance of the crystal around the optical axis. Specializing the obtained general expression for the z component of the angular momentum flux to the case of a paraxial beam propagating along the optical axis, we find that the expression is the same as the corresponding one for a paraxial beam propagating in an isotropic medium of refractive index n(o) (ordinary refractive index of the crystal); besides, we show that the flux is conserved during propagation and that it decomposes into the sum of an intrinsic and an orbital contribution. Investigating their dynamics we demonstrate that they are coupled and, during propagation, an exchange between them exists.