Can Nanotechnology Shine a New Light on Antimicrobial Photodynamic Therapies?

Recent developments in light‐controlled therapies (e.g., photodynamic and photothermal therapies) provide promising strategies to prevent and suppress bacterial infections, which are a leading cause of morbidity and mortality. Antibacterial photodynamic therapy (aPDT) has drawn increasing attention from the scientific society for its potential to kill multidrug‐resistant pathogenic bacteria and for its low tendency to induce drug resistance. In this chapter, we summarize the mechanism of action of aPDT, the photosensitizers, as well the current developments in terms of treating Gram‐positive and Gram‐negative bacteria. The chapter also describes the recent progress relating to photomedicine for preventing bacterial infections and biofilm formation. We focus on the laser device used in aPDT and on the light‐treatment parameters that may have a strong impact on the results of aPDT experiments. In the last part of this chapter, we survey on the various nanoparticles delivering photoactive molecules, and photoactive‐nanoparticles that can potentially enhance the antimicrobial action of aPDT

Impact of waveguide cross section on nonlinear impairments in integrated optical filters for WDM communication systems

Integrated optical chips enabling the realization of low-cost optical network units (ONU) is of great interest both for data centre solutions and for passive optical networks. In particular, in the frame of passive optical networks an interesting possibility is constituted by the presence, in the ONU of a Wavelength Division Multiplexing (WDM) filter [1] One of the most popular solution is based on a micro-ring resonators. The filter doesn’t introduce any relevant impairment in the downstream signal, as the optical power reaching the ONU, at the resonant wavelength, is generally so small that nonlinear effects can be generally neglected. Nevertheless, if the upstream signal, that generally has a much higher power, has to pass through the same resonator can undergo nonlinear effects like two-photon absorption (TPA), free-carriers absorption (FCA), and free-carrier dispersion (FCD) [2]. In this abstract we show the results of an experimental analysis we carried out in order to investigate the impact of optical nonlinear effects in WDM integrated micro-filters exploiting different designs (double- and triple- resonators structures, racetracks, rings, curved coupling regions, etc.) and exhibiting significantly different waveguide cross-sections (from 500 × 220 nm to 825 × 100 nm). The nonlinear behaviour evaluation has been carried out by performing two different sets of experiments. In the first one the amplified spontaneous emission emitted by an Er-doped fiber amplifier was filtered (by using a tunable filter with 5 nm band-width) and then amplified and then input by grating-assisted coupling to the filtering structures. Changes of filter transfer function were observed as a function of the input power. Conversely, in the second setup a narrowband CW-laser was used, and the behaviour of output power as a function of the input power was recorded

Soft proton exchanged channel waveguides in congruent lithium tantalate for frequency doubling

We report on stable optical waveguides fabricated by soft-proton exchange in periodically-poled congruent lithium tantalate in the α-phase. The channel waveguides are characterized in the telecom wavelength range in terms of both linear properties and frequency doubling. The measurements yield a nonlinear coefficient of about 9.5pm/V, demonstrating that the nonlinear optical properties of lithium tantalate are left nearly unaltered by the process

Roadmap for optofluidics

Optofluidics, nominally the research area where optics and fluidics merge, is a relatively new research field and it is only in the last decade that there has been a large increase in the number of optofluidic. applications, as well as in the number of research groups, devoted to the topic. Nowadays optofluidics applications include, without being limited to, lab-on-a-chip devices, fluid-based and controlled lenses, optical sensors for fluids and for suspended particles, biosensors, imaging tools, etc. The long list of potential optofluidics applications, which have been recently demonstrated, suggests that optofluidic technologies will become more and more common in everyday life in the future, causing a significant impact on many aspects of our society. A characteristic of this research field, deriving from both its interdisciplinary origin and applications, is that in order to develop suitable solutions a. combination of a deep knowledge in different fields, ranging from materials science to photonics, from microfluidics to molecular biology and biophysics,. is often required. As a direct consequence, also being able to understand the long-term evolution of optofluidics research is not. easy. In this article, we report several expert contributions on different topics. so as to provide guidance for young scientists. At the same time, we hope that this document will also prove useful for funding institutions and stakeholders. to better understand the perspectives and opportunities offered by this research field

Roadmap for Optical Tweezers 2023

Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration

Roadmap on all-optical processing

The ability to process optical signals without passing into the electrical domain has always attracted the attention of the research community. Processing photons by photons unfolds new scenarios, in principle allowing for unseen signal processing and computing capabilities. Optical computation can be seen as a large scientific field in which researchers operate, trying to find solutions to their specific needs by different approaches; although the challenges can be substantially different, they are typically addressed using knowledge and technological platforms that are shared across the whole field. This significant know-how can also benefit other scientific communities, providing lateral solutions to their problems, as well as leading to novel applications. The aim of this Roadmap is to provide a broad view of the state-of-the-art in this lively scientific research field and to discuss the advances required to tackle emerging challenges, thanks to contributions authored by experts affiliated to both academic institutions and high-tech industries. The Roadmap is organized so as to put side by side contributions on different aspects of optical processing, aiming to enhance the cross-contamination of ideas between scientists working in three different fields of photonics: optical gates and logical units, high bit-rate signal processing and optical quantum computing. The ultimate intent of this paper is to provide guidance for young scientists as well as providing research-funding institutions and stake holders with a comprehensive overview of perspectives and opportunities offered by this research field

Unifying theory of compensation techniques for intrachannel nonlinear effects

We show a new graphical method to identify and create configurations yielding to nonlinearity compensation in a fiber transmission system. Method validity is shown with regards to different link configurations and different compensation techniques. It is demonstrated that a unifying principle can always be applied, because only one physical effect is involved, even if different practical arrangements are proposed. Disclosed method allows gaining physical insight and can be applied to derive new compensation techniques; two examples of configurations derived using the proposed technique are also reported

Nonlinearity Compensation in a Fiber Optic Link by Optical Phase Conjugation

This article is intended as a guide to the techniques for nonlinearity compensation in a fiber-optic communication link based on optical phase conjugation. In the first part, the basics of the phase conjugation process are illustrated from both a mathematical and physical point of view. Then, the more commonly used devices for optical phase conjugation are described, with particular attention to the devices based on periodically poled lithium niobate waveguides. Subsequently, the applications of optical phase conjugation to the nonlinearity compensation of amplitude-modulated and phase-modulated signals are analyzed