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Early psoriatic arthritis (PsA) diagnosis is critical to prescribe timely treatment to prevent the irreversible joint damage and the many other problems that patients with PsA experience. This retrospective study aimed to highlight the benefits of a Rheuma-Derma Clinic focused on the early diagnosis and prompt treatment of PsA with a shared approach among Italian psoriasis patients. Diagnosing PsA early is the main goal to reduce joint damage and disability in the patients affected. Studies describing the results of rheuma-derma clinics aimed to reach this goal emerged in the last decade. This study presents limitations and advantages typical of retrospective designs.A Rheuma-Derma Clinic was created in 2017 at the Rheumatology Department of the Hospital Policlinico Gaspare Rodolico of the University of Catania in San Marco, Italy. This study compared the number of patients under disease-modifying antirheumatic treatment 5 years before and after the joint clinic was created. A rheumatologist and dermatologist simultaneously assessed patients with psoriasis and/or PsA to obtain a rapid multidisciplinary diagnostic approach and a shared therapeutic strategy. In addition, demographic, clinical, and clinimetrics data were collected.The number of patients with PsA receiving biological disease-modifying antirheumatic drugs increased 47% (from 255 to 374 patients) before and after the joint clinic was implemented. Likewise, those receiving conventional synthetic disease-modifying antirheumatic drugs increased by 47% (from 367 to 539) as well. Additionally, for all the clinimetrics evaluated (DAS28, HAQ, BASDAI, DAPSA, PASI, PGA), there was an improvement over the 12 months under the Rheuma-Derma Clinic care. The measures that improved the most were DAPSA, PGA, PASI, and BASDAI.The implementation of the Rheuma-Derma Clinic was associated with an increase in the number of patients diagnosed, the number of patients with PsA receiving DMARD treatments, and improvements in clinimetrics among the study participants.

Introduction: Enthesitis and dactylitis are difficult-to-treat features of psoriatic arthritis (PsA), leading to disability and affecting quality of life. Objective: The aim of this study is to evaluate enthesitis (using the Leed enthesitis index (LEI)) and dactylitis at 6 and 12 months in patients treated with apremilast. Methods: Patients affected by PsA from fifteen Italian rheumatological referral centers were screened. The inclusion criteria were: (a) enthesitis or dactylitisphenotype; (b) treatment with apremilast 30 mg bid. Clinical and treatment history, including PsA disease activity, were recorded. Mann–Whitney and chi-squared tests were used to assess the differences between independent groups, and Wilcoxon matched pairs signed-rank test assessed the differences between dependent samples. A p-value of

There are few real-world setting studies focused on apremilast effectiveness (i.e., retention rate) in psoriatic arthritis (PsA). The main aim of this retrospective observational study is the assessment of apremilast 3-year retention rate in real-world PsA patients. Moreover, the secondary objective is to report the reasons of apremilast discontinuation and the factors related to treatment persistence.In fifteen Italian rheumatological referral centers, all PsA consecutive patients who received apremilast were enrolled. Anamnestic data, treatment history, and PsA disease activity (DAPSA) at baseline were recorded. The Kaplan-Meier curve and the Cox analysis computed the apremilast retention rate and treatment persistence-related risk factors. A p-value 0.05 was considered statistically significant.The 356 enrolled patients (median age 60 [interquartile range IQR 52-67] yrs; male prevalence 42.7%) median observation period was 17 [IQR 7-34] months (7218 patients-months). The apremilast retention rate at 12, 24, and 36 months was, respectively, 85.6%, 73.6%, and 61.8%. The main discontinuation reasons were secondary inefficacy (34% of interruptions), gastro-intestinal intolerance (24%), and primary inefficacy (19%). Age and oligo-articular phenotype were related to treatment persistence (respectively hazard ratio 0.98 IQR 0.96-0.99; p = 0.048 and 0.54 IQR 0.31-0.95; p = 0.03).Almost three-fifths of PsA patients receiving apremilast were still in treatment after 3 years. This study confirmed its effectiveness and safety profile. Apremilast appears as a good treatment choice in all oligo-articular PsA patients and in those ones burdened by relevant comorbidities. Key Points • Apremilast retention rates in this real-life cohort and trials are comparable. • The oligo-articular phenotype is associated with long-lasting treatment (i.e., 3 years). • No different or more prevalent adverse events were observed.

We report on the theoretical and experimental demonstration of parametric driving of Kerr cavity solitons in a singly-resonant optical parametric oscillator with competing nonlinearities. We leverage this new configuration to perform random number generation.

Temporal cavity solitons are optical pulses that propagate indefinitely in nonlinear resonators. They are currently attracting a lot of attention, both for their many potential applications and for their connection to other fields of science. Cavity solitons are phase locked to a driving laser. This is what distinguishes them from laser dissipative solitons and the main reason why they are excellent candidates for precision applications such as optical atomic clocks. To date, the focus has been on driving Kerr solitons close to their carrier frequency, in which case a single stable localised solution exists for fixed parameters. Here we experimentally demonstrate, for the first time, Kerr cavity solitons excitation around twice their carrier frequency. In that configuration, called parametric driving, two solitons of opposite phase may coexist. We use a fibre resonator that incorporates a quadratically nonlinear section and excite stable solitons by scanning the driving frequency. Our experimental results are in excellent agreement with a seminal amplitude equation, highlighting connections to hydrodynamic and mechanical systems, amongst others. Furthermore, we experimentally confirm that two different phase-locked solitons may be simultaneously excited and harness this multiplicity to generate a string of random bits, thereby extending the pool of applications of Kerr resonators to random number generators and Ising machines.

This work proposes a new route to overcome the limits of the thermal poling technique for the creation of second order nonlinearity in conventional silica optical fibers. We prove that it is possible to enhance the nonlinear behavior of periodically poled fibers merging the effects of poling with the nonlinear intrinsic properties of some materials, such as MoS2, which are deposited inside the cladding holes of a twin-hole silica fiber. The optical waves involved in a second harmonic generation process partially overlap inside the thin film of the nonlinear material and exploit its higher third order susceptibility to produce an enhanced SHG., SCOPUS: ar.j, info:eu-repo/semantics/published

The management of patients with immuno-rheumatological diseases has profoundly changed during the COVID-19 pandemic and telemedicine has played an important role in the disease follow-up. In addition to monitoring disease activity and any adverse events, especially infectious events, assessing the psychological situation of the patient can be fundamental. Furthermore, COVID-19 has a serious impact on mental health and, since the beginning of the pandemic, a significantly higher incidence of anxiety disorders and depressive symptoms especially in younger people was observed. In this study, we evaluated the incidence of depressive disorders, anxiety, and fibromyalgia (FM) in our patients with rheumatoid arthritis and psoriatic arthritis during the lockdown period due to the COVID-19 pandemic and we validate the use of telemedicine in the clinical management of these patients. Mental and physical stress during the COVID-19 pandemic can greatly worsen FM symptoms and intensify patients’ suffering without a clinical flare of the inflammatory disease for patients affected by rheumatoid arthritis. Telemedicine has allowed us to identify patients who needed a face-to-face approach for therapeutic reevaluation even if not related to a flare of the inflammatory disease. Even if our data does not allow us to draw definitive conclusions regarding the effectiveness of telemedicine as greater than or equal to the standard face-to-face approach, we continue to work by modifying our approach to try to ensure the necessary care in compliance with safety and, optimistically, this tool will become an important part of rheumatic disease management.

The hollow regions of an anti-resonant fiber (ARF) offer an excellent template for the deposition of functional materials. When the optical properties of such materials can be modified via external stimuli, it offers a method to control the transmission properties of the fiber device. In this Letter, we show that the integration of a M o S 2 film into the ARF voids allows the fiber to act as an electro-optical modulator. We record a maximum modulation depth of 3.5 dB at 744 nm, with an average insertion loss of 7.5 dB.

In this retrospective compendium, we attempt to draw a “fil rouge” along fifteen years of our research in the field of optical feedback interferometry aimed at guiding the readers to the verge of new developments in the field. The general reader will be moved at appreciating the versatility and the still largely uncovered potential of the optical feedback interferometry, for both sensing and imaging applications. By discovering the broad range of available wavelengths (0.4–120 μm), the different types of suitable semiconductor lasers (Fabry–Perot, distributed feedback, vertical-cavity, quantum-cascade), and a number of unconventional tenders in multi-axis displacement, ablation front progression, self-referenced measurements, multispectral, structured light feedback imaging and compressive sensing, the specialist also could find inspirational suggestions to expand his field of research.

This erratum corrects the mistyped pump repetition rate in Opt. Lett.42, 4671 (2017)OPLEDP0146-959210.1364/OL.42.004671.

When a signal propagates through a transmission line, it is deteriorated by amplitude and phase noise, which reduces its signal-to-noise ratio (SNR) [1]. According to Shannon's theory, the SNR determines the maximum spectral efficiency. It is therefore necessary to limit the noise [3]. For this purpose, one can use phase sensitive amplifiers (PSA) instead of phase insensitive amplifiers (PIA) like Erbium-doped fiber amplifiers. PSAs amplify only one phase quadrature of the signal while deamplifying the other, thanks to a required phase relationship between the pump and the signal. This unique property, known as phase-squeezing, allows to obtain noise figures (NF) as low as 0 dB whereas PIAs, based on stimulated emission, cannot be go below the 3 dB quantum limit [2]. Moreover, the phase-squeezing property of PSAs can be used for quantum communication or even in metrology [1]. PSA can be realized with χ(2) material through degenerate parametric amplification [2]. The large spectral separation between the pump and the signal makes it very easy to filter out the pump after amplification. A ± 11 dB amplification with a sub-quantum NF and a regeneration of a DPSK signal was experimentally performed in LiNbO3 [3]. A fiber based approach would however be preferable for telecommunication purposes. PSA's based on four wave-mixing have been demonstrated, but the long length and the difficulty to separate pump from the signal [1] hinders its practical implementation. Here we present the first demonstration of a PSA based on periodically poled silica fiber (PPSF). This design has the advantage of all-fiber devices as well as simple pump filtering. The experimental set-up is depicted in Figure 1. A 20 mW CW fiber laser at 1550 nm is sent through a 99:1 coupler to be divided into a signal and a pump. The pump is modulated into 1 ns wide pulses with a repetition rate of 50 MHz. It is then amplified and frequency doubled in a PPLN crystal. The peak power of the 775 nm pump pulses reaches 10W. The pump and CW signal are then combined in a WDM and sent through a 30 cm long PPSF [4] where the signal undergoes parametric amplification. A second WDM is used to separate the pump from the amplified signal. The wave plates and the polarization controller in the pump path, allow to simultaneously control the polarization of the pump and the power in the fundamental mode of the PPSF (at 775 nm the fibre is slightly multimode). The relative phase between the pump and signal is controlled by fine tuning the frequency of the laser via a built-in piezo.

Thermal poling of optical fibres is a well-known technique to create second order nonlinearity inside silica optical fibres, otherwise characterized by negligible nonlinear properties in the electric dipole approximation. Some recent work, realized by F. De Lucia et al., has introduced a new technique, designated as "Induction poling" [1] and with the adoption of liquid materials as embedded electrodes (both metallic and non-metallic) [2], allows thermal poling of optical fibres with any length and geometry. Despite these advances, thermal poling still represents a technological challenge that needs to be continuously optimized and simplified. In this work we focus our attention on the optimization of the electrical configuration of thermal poling of single mode optical fibres. We consider the single-anode (S-A) configuration, where a single electrode is embedded inside one of the two cladding channels of the optical fibre and connected to the desired electrical potential, and the double-anode (D-A) configuration, introduced for the first time by W. Margulis et al. in 2009 [3] and later commonly adopted by the scientific community. Fig. 1(a) shows the dependence (numerically calculated with COMSOL Multiphysics) of the X2 eff on the poling duration for both electrode configurations and at two different positions. The key result of these simulations is that the final value (for extended poling times) of the X2 eff in S-A configuration is approximately double with respect to the one obtained in the D-A approach. Furthermore, the value at the centre of the fibre is almost zero in D-A configuration. We hypothesize that this behaviour arises from the mutually competitive evolution of the space-charge formation due to the presence of two anodes. In contrast, the S-A configuration does not suffer from this limitation. Experimentally for the first time the X2 eff was measured in a process of second harmonic generation (SHG) at 1550 nm in a fibre periodically poled in S-A configuration. The nonlinearity has been periodically erased via exposure to a UV light generated by a frequency doubled Argon-ion laser (CW, 244 nm). Fig. 1(c) shows the spectrum of the SHG light.

Anti-resonant fibres (ARFs) are of significant interest for state of the art photonic technologies. Mode guidance is largely confined to the air core, demonstrating very low optical losses [1]. Furthermore, their internal structure offers a large surface area and is thus ideal as a deposition template for the addition of novel functional materials which would be able to alter their waveguide properties. We have previously demonstrated that the deposition of thin silicon layers onto the inner regions of an ARF results in strong light-matter interaction [2]. In this work, we utilise this interaction to externally control the optical properties of the composite material ARF (CM-ARF). Here, 2D layers of MoS 2 were deposited on the inner (cladding) regions of the ARF as shown in Fig. 1(a). MoS 2 is a Transition Metal Dichalcogenide (TMDC) 2D material that exhibits many optoelectronic phenomena such as the electro-absorptive effect [3]. Although there are already a number of examples in which TMDCs are incorporated into optical fibre systems to exploit the third order optical nonlinearity of the material to create saturable absorbers [4], this requires large amounts of power to be absorbed by the film, which is usually placed on the end face of a fibre. In contrast, here we show clear modulation at very low power.

The development of hollow core optical fibers (HCs) based on the antiresonant optical principle is gaining a significant interest within the optical fiber research community due, among others, to their broadband transmission, mid-infrared and ultra-violet operation, as well as their unique ability to handle high optical power. In this work, we offer an update on our recent activities related to the introduction of novel HCs designs, the fabrication of HCs based on composite materials and, in particular, to the development of novel HCs for mid-infrared transmission. These novel forms of optical fibers may unable a range of novel, still unexplored applications.

We compare several thermal poling configurations, demonstrating that a single-anode geometry offers high effective Chi(2) even in optical fibers with loose manufacturing tolerances. Our modelling also reveals that PC fibers display an unexpected “inhibited poling” mechanism.

We simulate and experimentally demonstrate deep UV generation from a 1550 nm laser source in a fully fiberized system by cascading second and third harmonic generation using a periodically poled silica fiber and an optical sub-micron diameter fiber. Harmonic generation is achieved by harnessing intermodal phase matching in optical microfibers and a permanent χ(2) induced via thermal poling. As a result, efficient non-linear processes can be observed despite the low third-order nonlinear susceptibility of silica glass.

UV light has been generated in optical fibers using nonlinear optics (harmonic generation) and rare earth doping with Gd3+ Asia Communications and Photonics Conferene (ACP)

UV generation via four-wave-mixing (FWM) in optical microfibres (OMFs) was demonstrated. This was achieved by exploiting the tailorable dispersion of the OMF in order to phase match the propagation constant of the four frequencies involved in the FWM process. In order to satisfy the frequency requirement for FWM, a Master Oscillator Power Amplifier (MOPA) working at the telecom C-band was connected to a periodically poled silica fibre (PPSF), producing a fundamental frequency (FF) at 1550.3nm and a second harmonic (SH) frequency at 775.2nm. A by-product of this second harmonic generation is the generation of a signal at the third harmonic (TH) frequency of 516.7nm via degenerate FWM. This then allows the generation of the fourth harmonic (FH) at 387.6nm and the fifth harmonic (5H) at 310nm via degenerate and nondegenerate FWM in the OMF.The output of the PPSF was connected to a pure silica core fibre which was being tapered using the modified flame brushing technique from an initial diameter of 125µm to 0.5µm. While no signal at any UV wavelength was initially observed, as the OMF diameter reached the correct phase matching diameters, signals at 387.6nm appeared. Signals at 310nm also appeared although it is not phase matched, as the small difference in the propagation constant is bridged by other nonlinear processes such as self-phase and cross phase modulation.

Four-Wave-Mixing (FWM) is enhanced by tailoring the modal effective index in optical microfibers to improve the phase matching conditions. An enhancement of >25dB was recorded in a 6-mm-long optical microfiber.

We report on the development of an all-interferometric optomechatronic sensor for the detection of multi-degrees-of-freedom displacements of a remote target. The prototype system exploits the self-mixing technique and consists only of a laser head, equipped with six laser sources, and a suitably designed reflective target. The feasibility of the system was validated experimentally for both single or multi-degrees-of-freedom measurements, thus demonstrating a simple and inexpensive alternative to costly and bulky existing systems.

Four-wave mixing (FWM) based parametric amplification in optical microfibers (OMFs) is demonstrated over a wavelength range of over 1000 nm by exploiting their tailorable dispersion characteristics to achieve phase matching. Simulations indicate that for any set of wavelengths satisfying the FWM energy conservation condition there are two diameters at which phase matching in the fundamental mode can occur. Experiments with a high-power pulsed source working in conjunction with a periodically poled silica fiber (PPSF), producing both fundamental and second harmonic signals, are undertaken to investigate the possibility of FWM parametric amplification in OMFs. Large increases of idler output power at the third harmonic wavelength were recorded for diameters close to the two phase matching diameters. A total amplification of more than 25 dB from the initial signal was observed in a 6 mm long optical microfiber, after accounting for the thermal drift of the PPSF and other losses in the system.

The generation of UV light in solid core silica fibres has been achieved using four wave mixing in optical fibre tapers or rare earth doping with Gd3+.

We study novel designs of hollow-core antiresonant fibers comprising multiple materials in their core-boundary membrane. We show that these types of fibers still satisfy an antiresonance condition and compare their properties to those of an ideal single-material fiber with an equivalent thickness and refractive index. As a practical consequence of this concept, we discuss the first realization and characterization of a composite silicon/glass-based hollow antiresonant fiber.

We consider a multi-transverse mode Vertical Cavity Surface Emitting Laser (VCSEL) subject to optical feed-back. When the “eld pro“le can be described in terms of few Gauss-Laguerre modes we show that the self-mixinginterferometric signal exhibits features peculiar of the spatial distribution and/or polarization state of the re-injected “eld. Based on these results we provide both theoretically and experimentally the proof-of-principle ofan operational scheme for a sensor that can be used to simultaneously measure target translations along theoptical axis and target rotations in the orthogonal plane.Keywords: Semiconductor laser dynamics, optical feedback, sensors 1. INTRODUCTION The self-mixing interferometry in conventional diode lasers has been largely exploited for the realization ofcompact, contactless, sensors for real time and high precision measurements of e.g absolute distance, vibration,rotations. 1 In presence of moderate optical feedback provided by an external moving target, the laser intensityshows regular interference fringes separated by half the wavelength whose number provides a measure of thetarget displacement. Moreover, there exist certain feedback regimes where the interferometric signal has anasymmetric sawtooth behavior revealing the direction of the target motion. In order to measure simultaneouslytarget displacements with more than one degree of freedom, customized multi-sources con“gurations have beenproposed.

The recent development of ultrafast laser ablation technology in precision micromachining has dramatically increased the demand for reliable and real-time detection systems to characterize the material removal process. In particular, the laser percussion drilling of metals is lacking of non-invasive techniques able to monitor into the depth the spatial- and time-dependent evolution all through the ablation process. To understand the physical interaction between bulk material and high-energy light beam, accurate in-situ measurements of process parameters such as the penetration depth and the removal rate are crucial. We report on direct real time measurements of the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metals by implementing a contactless sensing technique based on optical feedback interferometry. High aspect ratio micro-holes were drilled onto steel plates with different thermal properties (AISI 1095 and AISI 301) and Aluminum samples using 120-ps/110-kHz pulses delivered by a microchip laser fiber amplifier. Percussion drilling experiments have been performed by coaxially aligning the diode laser probe beam with the ablating laser. The displacement of the penetration front was instantaneously measured during the process with a resolution of 0.41 μm by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

Real time simultaneous measurement by remote laser source of long range longitudinal displacement and small angle wobbling of a sliding target is demonstrated. The compact self-aligned laser-self-mixing interferometer achieves 0.8 µm axial resolution over 1 m linear and 17 µrad of pitch and yaw resolution over 2 mrad angular ranges, respectively.

Direct real-time measurements of the penetration depth during laser micromachining has been demonstrated by developing a novel ablation sensor based on laser diode feedback interferometry. Percussion drilling experiments have been performed by focusing a 120-ps pulsed fiber laser onto metallic targets with different thermal conductivity. In-situ monitoring of the material removal rate was achieved by coaxially aligning the beam probe with the ablating laser. The displacement of the ablation front was revealed with sub-micrometric resolution by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

We demonstrate that a non-invasive sensing technique based on optical feedback interferometry is capable to instantaneously measure the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metallic plates. The sawtooth-like modulation of the interferometric signal out of the detecting sensor has been analyzed to reveal the time dependence of the removal depth with sub-micrometric resolution. Various dynamic factors related to the influence of laser pulse duration and peak energy have been assessed by in-situ spatial- and time-dependent characterization all through the ablation process. The importance of real-time measurement of the ablation rate is crucial to improve the basic understanding of ultrafast laser-material interactions. Moreover, the detection system results high-sensitive, compact, and easily integrable in most industrial workstations, enabling the development of on-line control to improve the ablation efficiency and the quality of laser micro-machining processes.We demonstrate that a non-invasive sensing technique based on optical feedback interferometry is capable to instantaneously measure the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metallic plates. The sawtooth-like modulation of the interferometric signal out of the detecting sensor has been analyzed to reveal the time dependence of the removal depth with sub-micrometric resolution. Various dynamic factors related to the influence of laser pulse duration and peak energy have been assessed by in-situ spatial- and time-dependent characterization all through the ablation process. The importance of real-time measurement of the ablation rate is crucial to improve the basic understanding of ultrafast laser-material interactions. Moreover, the detection system results high-sensitive, compact, and easily integrable in most industrial workstations, enabling the development of on-line control to improve the ablation efficiency and the quality of laser micro-machini...

We demonstrate that diode laser self-mixing interferometry can be exploited to instantaneously measure the ablation front displacement and the laser ablation rate during ultrafast microdrilling of metals. The proof of concept was obtained using a 50-μm-thick stainless steel plate as the target, a 120 ps/110 kHz microchip fiber laser as the machining source, and an 823 nm diode laser with an integrated photodiode as the probe. The time dependence of the hole penetration depth was measured with a 0.41 µm resolution.

We report on the development of an all-interferometric sensor based on the laser-self-mixing for the simultaneous detection of multi-degrees-of-freedom displacement of a remote target. The prototype system consists only of a laser head, equipped with 6 diode lasers and a properly designed reflective target. Information on a single degree-of-freedom motion is extracted by the differential measurement of two linear displacements by means of two nominally identical self-mixing interferometers. The sensor has been experimentally tested to measure yaw, pitch, roll, straightness and flatness corrections over a continuous linear range of 1 m, with resolutions of 0.7 μm (longitudinal), 20 μm (straightness and flatness), 0.001° (yaw and pitch) and 0.015 °(roll).

The development of a contactless sensor based on the Laser-Self-Mixing effect for the simultaneous measurement of linear and transverse degrees-of-freedom (DOFs) of a moving target is described in this paper. The sensor is made of three laser diodes with integrated monitor photodiodes, and a properly designed reflective target attached to the moving object. The proposed technique exploits the differential measurement of linear displacements by two identical self-mixing interferometers (SMIs) and makes the system more compact and easier to align with respect to traditional interferometric systems, thus providing an effective low-cost motion control system. The feasibility of the proposed sensor is experimentally demonstrated over a range of 1 m for linear motion and ± 6 mm for transverse displacements, with resolutions of 0.7 μm and 20 μm, respectively.

We present a contactless optical sensor based on the laser-self-mixing effect for real-time measurement of linear and transverse displacements of a moving stage. The sensor is able to measure linear displace- ments of up to 400 mm along the main optical axis while simultaneously estimating straightness and flatness deviations up to 1 mm. The sensor exploits two identical coplanar nonparallel self-mixing inter- ferometers and requires only one reference plane. The reduction in the number of optical elements al- lowed by the self-mixing configuration and the intrinsic stiffness of the adopted geometry result in a compact, low-cost, and easy-to-align setup.

We demonstrate that a single all-optical sensor based on laser diode self-mixing interferometry can monitor the independent displacement of individual portions of a surface. The experimental evidence was achieved using a metallic sample in a translatory motion while partly ablated by a ps-pulsed fiber laser. A model based on the Lang-Kobayashi approach gives an excellent explanation of the experimental results.