Compact angled multimode interference duplexers for multi-gas sensing applications.

A compact, low-loss 2 × 1 angled-multi-mode-interference-based duplexer is proposed as an optical component for integrating several wavelengths with high coupling efficiency. The self-imaging principle in multimode waveguides is exploited to combine two target wavelengths, corresponding to distinctive absorption lines of important trace gases. The device performance has been numerically enhanced by engineering the geometrical parameters, offering trade-offs in coupling efficiency ratios. The proposed designs are used as versatile duplexers for detecting gas combinations such as ammonia-methane, ammonia-ethane, and ammonia-carbon dioxide, enabling customization for specific sensing applications. The duplexers designed are then fabricated and characterized, with a special focus on assessing the impact of the different target wavelengths on coupling efficiency.

Enhanced Fano resonances in a silicon nitride photonic crystal nanobeam-assisted micro ring resonator for dual telecom band operation.

Silicon-based Micro Ring Resonators (MRR) are a powerful tool for the realization of label free optical biosensors. The sharp edge of a Fano resonance in a Silicon Nitride (Si3N4) platform can boost photonic sensing applications based on MRRs. In this work, we demonstrate enhanced Fano resonance features for a Si3N4 Micro Ring Resonator assisted by a Photonic Crystal Nanobeam (PhCN-MRR) operating in the TM-like mode at the O-band wavelengths. Our findings show that the fabricated PhCN-MRR results in increased asymmetric resonances for TM-like mode compared with TE-like mode operation in the C-band. As a result, a versatile and flexible design to realize Fano resonance with polarization dependent asymmetry in the C and O telecom bands is presented.

Design and Fabrication of a Flexible Gravimetric Sensor Based on a Thin-Film Bulk Acoustic Wave Resonator.

Sensing systems are becoming less and less invasive. In this context, flexible materials offer new opportunities that are impossible to achieve with bulky and rigid chips. Standard silicon sensors cannot be adapted to curved shapes and are susceptible to big deformations, thus discouraging their use in wearable applications. Another step forward toward minimising the impacts of the sensors can be to avoid the use of cables and connectors by exploiting wireless transmissions at ultra-high frequencies (UHFs). Thin-film bulk acoustic wave resonators (FBARs) represent the most promising choice among all of the piezoelectric microelectromechanical system (MEMS) resonators for the climbing of radio frequencies. Accordingly, the fabrication of FBARs on flexible and wearable substrates represents a strategic step toward obtaining a new generation of highly sensitive wireless sensors. In this work, we propose the design and fabrication of a flexible gravimetric sensor based on an FBAR on a polymeric substrate. The resonator presents one of the highest electromechanical coupling factors in the category of flexible AlN-based FBARs, equal to 6%. Moreover, thanks to the polymeric support layer, the presence of membranes can be avoided, which leads to a faster and cheaper fabrication process and higher robustness of the structure. The mass sensitivity of the device was evaluated, obtaining a promising value of 23.31 ppm/pg. We strongly believe that these results can pave the way to a new class of wearable MEMS sensors that exploit ultra-high-frequency (UHF) transmissions.

Holographic Manipulation of Nanostructured Fiber Optics Enables Spatially-Resolved, Reconfigurable Optical Control of Plasmonic Local Field Enhancement and SERS.

Integration of plasmonic structures on step-index optical fibers is attracting interest for both applications and fundamental studies. However, the possibility to dynamically control the coupling between the guided light fields and the plasmonic resonances is hindered by the turbidity of light propagation in multimode fibers (MMFs). This pivotal point strongly limits the range of studies that can benefit from nanostructured fiber optics. Fortunately, harnessing the interaction between plasmonic modes on the fiber tip and the full set of guided modes can bring this technology to a next generation progress. Here, the intrinsic wealth of information of guided modes is exploited to spatiotemporally control the plasmonic resonances of the coupled system. This concept is shown by employing dynamic phase modulation to structure both the response of plasmonic MMFs on the plasmonic facet and their response in the corresponding Fourier plane, achieving spatial selective field enhancement and direct control of the probe's work point in the dispersion diagram. Such a conceptual leap would transform the biomedical applications of holographic endoscopic imaging by integrating new sensing and manipulation capabilities.

Design of vanadium-dioxide-based resonant structures for tunable optical response.

Phase change materials are suitable for tunable photonic devices where the optical response can be altered under external stimuli, such as heat, an electrical or an optical signal. In this scenario, we performed numerical simulations to study the optical properties of a flat unpatterned resonant structure and a grating, both coated with a thin film of vanadium dioxide (VO2). Our results suggest that it is possible to modulate broadband and narrowband reflectance spectra of the resonant structures in the visible to near-infrared range by more than 40 % when the VO2 undergoes an insulator-to-metal phase transition. Resonant devices with a tunable spectral response may find application in sensors, filters, absorbers, and detectors.

Congenital cysts of the lower male genitourinary tract: a disorder with various treatment approaches and pitfalls-case report.

BACKGROUND: The cysts of the male pelvic floor represent a rare clinical entity. Their origin is linked to an altered development of paramesonephric and mesonephric ducts during embryogenesis. CASE PRESENTATION: We report our experience regarding two patients presenting cysts of the ejaculatory system treated with open and mini-invasive surgery. The patients referred to our clinic with nonspecific symptoms and the diagnosis was obtained by radiological investigations. The patient treated with an open approach developed a pelvic purulent collection and a fistula of the prostatic urethra, managed with surgical drainage and prolonged bladder catheterization. On the other hand, the patient treated with laparoscopic approach did not develop any complications. No sexual or ejaculatory disorders were reported. CONCLUSIONS: Patients with congenital cysts of the pelvic floor must be adequately informed about the risks and benefits of surgery and a careful counseling is mandatory before surgery. Treatment is recommended for symptomatic patients and an endoscopic approach is associated with a high rate of recurrence. A laparoscopic approach, when possible, is desirable.

Percutaneous and endoscopic combined treatment of bladder and renal lithiasis in mitrofanoff conduit.

INTRODUCTION AND OBJECTIVES: Treatment of bulky lithiasis in continent and non-continent urine storage reservoirs has been widely described and debated (1). Less is known about the optimal treatment in patients with a Mitrofanoff conduit. If voiding in these patients is incomplete, leading to recurrent symptomatic bacteriuria, formation of large lithiasis can be a common long-term complication (2, 3). MATERIALS AND METHODS: This video describes a 19-year-old woman who underwent major open surgery at the age of six, with the configuration of a continent intestinal reservoir with a Mitrofanoff conduit. In 2020, she was referred to our center with a large stone in the reservoir and a minor stone in the inferior left renal calyx. We decided to proceed using a percutaneous approach with an "endovision technique" puncture for the bladder stone, combined with a retrograde intrarenal surgery for the renal stone. The MIP System "M size" was used to perform the percutaneous procedure, thus allowing a single-step dilation. The puncture and the dilation were followed endoscopically with a flexible ureterorenoscope avoiding the use of x-rays. The procedure was carried out as follows. The first step consisted in the insertion of a hydrophilic guidewire through the Mitrofanoff conduit. A flexible ureterorenoscope was then inserted coaxial to the guidewire. The percutaneous puncture, using an 80G needle, was followed endoscopically. Two guidewires were inserted, the first as a safety guidewire and the second for the tract dilation. The "single-step" dilation technique using the MIP system was performed and followed endoscopically. For the bladder lithotripsy, a dual-action lithotripter that combines ultrasonic and mechanical energy was used. Finally, a flexible ureterorenoscope and a basket for the retrieval of a single inferior caliceal stone were used. The procedure ended after positioning a single J stent in the left kidney and a nephrostomy tube in the reservoir. RESULTS: The operative time was 80 minutes and the fluoroscopy time was 6 seconds. Hemoglobin and creatinine serum levels remained stable after the procedure and the patient was discharged on the third post-operative day, after removing both the single J and the nephrostomy tube. Follow-up lasted 12 months, with no bladder or renal stone recurrence, maintaining good continence of the Mitrofanoff conduit. CONCLUSION: In patients who have undergone several major surgeries a mini-invasive approach is advisable, not only for the morbidity of an open approach, but also for the increased risk of complications while handling an intestinal reservoir. Regarding a pure endoscopic approach, the passage of a nephroscope or a cystoscope through the Mitrofanoff conduit, combined with the continuous traction during the lithotripsy, could damage and compromise its continence. For this reason, the percutaneous approach is the most suitable method in these specific and rare cases.

Multifunctional and reconfigurable graphene/liquid crystal-assisted asymmetrical Fabry-Pérot cavity for reflected light control.

Multifunctional and reconfigurable devices are crucial for compact and smart optoelectronic devices. In this paper, we propose a multifunctional and spectrally reconfigurable asymmetric 1D PhC Fabry-Pérot cavity filled with nematic liquid crystal and bounded by two graphene monolayers. Due to the large number of available degrees of freedom, such a structure can behave as either a notch filter, an absorber, an amplitude modulator, or a phase shifter for the reflected electromagnetic waves. The chemical potential of one or both graphene monolayers can be exploited to modulate the amplitude and phase-shift angle of the reflected electromagnetic waves. Furthermore, all functions are narrowband (1 nm linewidth) and are spectrally tunable over a range of about 200 nm around the working wavelength of 1550 nm by controlling the orientation of the elongated molecules of the liquid crystal. This structure may be advantageously exploited for the realization of optical modulators and beamsteering systems.

The use of endoscopic combined intrarenal surgery as an additional approach to upper urinary tract urothelial carcinoma: Our Experience.

INTRODUCTION: With increasing experience and advancing technology, endoscopy for UTUC has become more common. Endoscopic Combined Intrarenal Surgery (ECIRS) could be an option for patients with low-grade and large-volume UTUC that could be either anatomically or technically challenging to manage by retrograde flexible ureterorenoscopy. MATERIALS AND METHODS: In this video, we describe, step by step, our ECIRS technique as applied to two selected clinical cases of UTUC. CONCLUSION: ECIRS could represent a useful approach to UTUC in selected cases. The advantage of the "endovision" puncture and dilation technique is in the avoidance of entering the renal calyx at the level of the tumor. In addition, the combined approach, compared to the purely percutaneous approach, allows access to, and treatment of, neoplasms located in all renal calyces.

High transmission from 2D periodic plasmonic finite arrays with sub-20 nm gaps realized with Ga focused ion beam milling.

Fabricating plasmonic nanostructures with good optical performances often requires lengthy and challenging patterning processes that can hardly be transferred to unconventional substrates, such as optical fiber tips or curved surfaces. Here we investigate the use of a single Ga focused ion beam process to fabricate 2D arrays of gold nanoplatelets for nanophotonic applications. While observing that focused ion beam milling of crossing tapered grooves inherently produces gaps below 20 nm, we provide experimental and theoretical evidence for the spectral features of grooves terminating with a sharp air gap. We show that transmission near 10% can be obtained via two-dimensional nano-focusing in a finite subset of 2D arrays of gold nanoplatelets. This enables the application of our nanostructure to detect variations in the refractive index of thin films using either reflected or transmitted light when a small number of elements are engaged.

Mesoscopic self-collimation along arbitrary directions and below the light line.

Self-collimation (SC) and mesoscopic self-collimation (MSC) have been successfully demonstrated along the directions of high symmetry of photonic crystals. Indeed, wide angular acceptances are obtained only in these directions which offer extremely flat isofrequencies. In this article, we numerically demonstrate that mesoscopic self-collimation with large angular acceptance can be achieved along arbitrary directions that are not of high symmetry. In particular, we propose a simple method that allows to easily find all the non-trivial collimation directions and corresponding frequencies. Thanks to the double periodicity of the mesoscopic crystal, these solutions can be effectively tailored in terms of direction and frequency. Moreover, non-trivial MSC solutions can be found well below the light cone. These MSC features open up the possibility of designing complex systems by combining different configurations, such as high reflection (HR) or anti reflection (AR) ones, or active materials.

Towards Portable Nanophotonic Sensors.

A range of nanophotonic sensors composed of different materials and device configurations have been developed over the past two decades. These sensors have achieved high performance in terms of sensitivity and detection limit. The size of onchip nanophotonic sensors is also small and they are regarded as a strong candidate to provide the next generation sensors for a range of applications including chemical and biosensing for point-of-care diagnostics. However, the apparatus used to perform measurements of nanophotonic sensor chips is bulky, expensive and requires experts to operate them. Thus, although integrated nanophotonic sensors have shown high performance and are compact themselves their practical applications are limited by the lack of a compact readout system required for their measurements. To achieve the aim of using nanophotonic sensors in daily life it is important to develop nanophotonic sensors which are not only themselves small, but their readout system is also portable, compact and easy to operate. Recognizing the need to develop compact readout systems for onchip nanophotonic sensors, different groups around the globe have started to put efforts in this direction. This review article discusses different works carried out to develop integrated nanophotonic sensors with compact readout systems, which are divided into two categories; onchip nanophotonic sensors with monolithically integrated readout and onchip nanophotonic sensors with separate but compact readout systems.

Link budget analysis of bi-directional LEO and GEO optical feeder links advancing the beam wander model's accuracy.

The telecommunications of the future rely on the concept of a three-dimensional architecture able to integrate terrestrial and non-terrestrial networks with the goal to ensure a reliable and high-speed connectivity to users located anywhere. In this context, free space optical communications constitute a candidate technology for feeder links, thanks to their advantages in terms of bandwidth and achievable data rates. Nonetheless, due to the propagation impediments encountered by an optical beam travelling through atmosphere, flexible and accurate instruments able to support the design of optical feeder links are needed. Therefore, in this paper a link budget numerical tool able to meet these requirements is presented and the link budget analysis for real optical feeder links is performed demonstrating its prediction accuracy by means of the comparison with experimental results for both low Earth orbit and geostationary Earth orbit based configurations. Finally, the limits of the conventional beam wander model are analyzed and overcome.

Numerical analysis of the coupling mechanism in long-range plasmonic couplers at 1.55 µm.

We study the coupling mechanism between a high refractive index contrast waveguide and a plasmonic thin-film waveguide in the IR range. We also propose a novel design of a vertical coupler based on loading the plasmonic waveguide with a high refractive index contrast medium on each side. We achieve a coupling efficiency and an insertion loss of about 95% and 0.2 dB, respectively, with a coupling length of only 2.85 µm at the working wavelength of 1.55 µm.

Gold strip gratings with binary supercell.

In this Letter, the study of a periodic structure composed of gold strips arranged in double-period unit cells, in a symmetric and asymmetric environment, is reported. The spectral maps show that the formation of the plasmonic bandgap and the extraordinary optical transmission are subjected to the proportion between the strip widths. Moreover, when the asymmetric environment is considered, high-transmittance and high-absorbance states arise. Hence, by controlling the geometrical parameters of the binary-periodic structure, it is possible to tailor the spectral response of the grating enhancing the desired features and exploiting them for different applications.

Design of optically transparent metasurfaces based on CVD graphene for mmWave applications.

We propose and numerically investigate a smart, optically transparent digital metasurface reflective in the mmWave range, based on CVD graphene programmable elements. For both TM and TE polarizations, we detail the optimization of the unit cells, designed to exhibit two distinct states that correspond to those of binary encoding. The whole metasurface encoding can be customized to provide different electromagnetic functions, such as wide-band beam splitting at a controlled angle and reduction of the Radar Cross Section. Optically transparent metasurfaces could be integrated and exploited in windows and transparent surfaces in future Beyond-5G and 6G ecosystems.

Highly efficient and selective integrated directional couplers for multigas sensing applications.

The design and fabrication of a compact, low-loss, broadband directional coupler (DC) based duplexer operating in the near-infrared (NIR) region are demonstrated. The duplexer exhibits high selectivity and coupling efficiency (CE), for target wavelengths of 1530 nm and 1653.7 nm, making it applicable in systems for the multi-gas detection of ammonia and methane. The measured CE for the duplexer is 73% and 76% at 1530 nm and 1653.7 nm respectively. These results demonstrate the effectiveness of the duplexer as a broadband and scalable power source for highly sensitive sensing techniques, like quartz-enhanced photoacoustic spectroscopy (QEPAS). Its compact size and low-loss characteristics make it highly portable and well-suited for drone-based multi-gas detection applications.

Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling.

The aim of the article is to examine the workability of sintered powder material of aluminum alloy (Alumix 321) through severe plastic deformations under the conditions of the equal channel angular rolling (ECAR) process. Accordingly, the stress-strain analysis of the ECAR was carried out through a computer simulation using the finite element method (FEM) by Deform 3D software. Additionally, the formability of the ALUMIX 321 was investigated using the diametrical compression (DC) test, which was measured and analyzed by digital image correlation and finite element simulation. The relationship between failure mode and stress state in the ECAR process and the DC test was quantified using stress triaxiality and Lode angle parameter. It is concluded that the sintered powder material during the ECAR processing failure by a shearing fracture because in the fracture location the stress conditions were close to the pure shear (η and θ¯ ≈ 0). Moreover, the DC test revealed the potential role as the method of calibration of the fracture locus for stress conditions between the pure shear and the axial symmetry compression.

Investigation of the Properties of 316L Stainless Steel after AM and Heat Treatment.

Additive manufacturing, including laser powder bed fusion, offers possibilities for the production of materials with properties comparable to conventional technologies. The main aim of this paper is to describe the specific microstructure of 316L stainless steel prepared using additive manufacturing. The as-built state and the material after heat treatment (solution annealing at 1050 °C and 60 min soaking time, followed by artificial aging at 700 °C and 3000 min soaking time) were analyzed. A static tensile test at ambient temperature, 77 K, and 8 K was performed to evaluate the mechanical properties. The characteristics of the specific microstructure were examined using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The stainless steel 316L prepared using laser powder bed fusion consisted of a hierarchical austenitic microstructure, with a grain size of 25 µm as-built up to 35 µm after heat treatment. The grains predominantly contained fine 300-700 nm subgrains with a cellular structure. It was concluded that after the selected heat treatment there was a significant reduction in dislocations. An increase in precipitates was observed after heat treatment, from the original amount of approximately 20 nm to 150 nm.

Wearable Heart Rate Monitoring Device Communicating in 5G ISM Band for IoHT.

Advances in wearable device technology pave the way for wireless health monitoring for medical and non-medical applications. In this work, we present a wearable heart rate monitoring platform communicating in the sub-6GHz 5G ISM band. The proposed device is composed of an Aluminium Nitride (AlN) piezoelectric sensor, a patch antenna, and a custom printed circuit board (PCB) for data acquisition and transmission. The experimental results show that the presented system can acquire heart rate together with diastolic and systolic duration, which are related to heart relaxation and contraction, respectively, from the posterior tibial artery. The overall system dimension is 20 mm by 40 mm, and the total weight is 20 g, making this device suitable for daily utilization. Furthermore, the system allows the simultaneous monitoring of multiple subjects, or a single patient from multiple body locations by using only one reader. The promising results demonstrate that the proposed system is applicable to the Internet of Healthcare Things (IoHT), and particularly Integrated Clinical Environment (ICE) applications.