Tyndall National Institute

We demonstrate a hybrid external cavity laser incorporating an integrated side coupled Fabry-Perot (SC-FP) resonator realised on a silicon nitride platform and coupled to a semiconductor optical amplifier. The SC-FP resonator achieves loaded quality factors of up to 6.5 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> with on-resonance reflectivity reaching 57%. The hybrid laser exhibits multi-wavelength emission aligned to the SC-FP resonances, with multiple longitudinal modes of the hybrid cavity competing within each resonance. When isolating single resonances, we observe coherent pulse trains with corresponding radiofrequency linewidth as narrow as ∼3 kHz. The system spontaneously generates multiple identical pulse profiles within the laser cavity, effectively multiplying the repetition rate. These results establish SC-FP resonators as promising wavelength-selective reflectors for compact, multi-wavelength hybrid laser systems with potential applications in frequency comb generation for telecommunication and precision spectroscopy.

We present transfer-printed LN-SiN hybrid racetrack microring resonators for nonlinear photonic applications. As a demonstration, green light is generated via frequency conversion using modal phase matching. Large-area LN transfer printing forms the hybrid platform, enabling nonlinear interactions for scalable, CMOS-compatible applications.

New types of 3D high-unloaded quality factor <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(Q_{u})}$</tex> half-cylindrical (HC) resonators and their application to compact and highly-performing bandpass filters (BPFs) are discussed. The proposed HC resonator concept has significantly smaller size and higher <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{Q_{u}}$</tex> /Vol than conventional cylindrical resonators. Thus, it can be used to realize highly-miniaturized and high-performing 3D BPFs. Further miniaturization and weight reduction is achieved through monolithic integration using stereolithography apparatus 3D printing. For proof-of-concept demonstration purposes, two second order BPFs (Topology 1,2) functionalizing different types of transfer functions were designed, manufactured and measured at X-band. They exhibited the following RF performance metrics: Topology 1: center frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(f_{c})}$</tex>: 11 GHz, 3-dB fractional bandwidth (FBW): 2.3%, minimum in-band insertion loss (IL): 0.29 dB (effective quality factor <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(Q_{eff})}$</tex>: 1,950), Topology 2: <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{f_c}$</tex>: 11.1 GHz, 3-dB FBW: 3.6%, in-band IL: 0.18 dB <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(Q_{eff}:1,880).}$</tex>

This study presents the in vitro and preliminary ex vivo development of a novel microneedle-based pH sensor for continuous intrapartum fetal monitoring. The objective was to evaluate the feasibility of using microneedle sensors to monitor fetal pH during labour and to develop a proof-of-principle microneedle pH sensor that meets clinical requirements such as high sensitivity to small pH changes (0.05 units) within a relevant range (6.50-7.45), minimal tissue disruption, and a compact design suitable for transcervical placement on the fetal scalp (<40 mm diameter). Platinum microneedles were passivated with ArCare medical adhesive and coated with iridium oxide via electrodeposition. Sensitivity was tested in phosphate buffered saline (PBS) and artificial interstitial fluid (ISF), using both external Ag/AgCl and internal platinum pseudo-reference electrodes. In PBS, the sensor exhibited linear responses in increments of 0.05 pH units over the clinically relevant range (6.5-7.45), with slopes of -60.49 mV/pH (R2 = 0.946, accuracy = 97.65%) and -63.2 mV/pH (R2 = 0.910, accuracy = 93.70%) in the external and internal configurations, respectively. In ISF, a slope of -25.5 mV/pH (R2 = 0.979) was obtained. Ex vivo testing on human skin confirmed successful microneedle penetration without visible iridium oxide transfer or tissue damage, as indicated by methylene blue staining. These findings support the potential for continuous minimally invasive fetal pH monitoring during labour, representing a significant step toward more objective and specific intrapartum assessment.

Supplying energy to IoT sensors presents a critical challenge, not only due to the difficulty of providing power sources to devices but also because the ever-growing number of devices is leading to a significant increase in total energy consumption. Assuming that each sensor battery lasts 10 years, the current number of devices would lead to millions of daily battery replacements. In this paper, we present how replacing traditional batteries with capacitors in LoRa-Based Energy Autonomous Wireless Sensor Nodes (EAWSNs), enabled by energy harvesting systems, can create maintenance-free solutions suitable for deployment in remote areas. Our solution uses lead-free and non-toxic piezoelectric materials to power ultra-low-power LoRa nodes. The advantage of this lead-free technology is that it enables an "install-and-forget" approach for devices in practically any application where vibration energy is available, including industrial machinery, vehicles, and bridge monitoring. Experimental results show that with an acceleration of 0.7 g and a storage capacitor of 4 mF, the EAWSN can, on average, send LoRa packets every 471 seconds. By combining vibration energy harvesting with ultra-low-power LoRa nodes, we aim to pave the way for sustainable IoT ecosystems, minimizing environmental impact while ensuring reliable and autonomous operation of sensor nodes.

Mid-infrared (Mid-IR) fingerprinting is commonly applied for identifying contaminants in food, detecting narcotics and explosives, and tracking diseases in agriculture. Despite its numerous advantages, traditional Mid-IR spectroscopy is severely limited by the bulky, vibration-sensitive Mid-IR spectrometers and the small absorption cross sections, which make it not suitable for measuring low analyte concentrations. In response to these challenges, Mid-IR metasurfaces are emerging as a promising technology, offering improved sensing capabilities that are applicable in a wide range of areas, such as biomedical diagnostics, industrial processes, and environmental monitoring. The metamaterial-based sensor components presented here are designed to target compounds within the wavelength range of 4 µm to 15 µm. Additionally, the design is compatible with UV photolithography, making it a practical platform for enhancing mid-IR spectroscopy.

A multiplexed, highly sensitive, and stable electrochemical sensors has been developed for the detection of glucose and lactate in biological fluids, enabling early screening of calf diseases such as Bovine respiratory disease (BRD) and scour. The device incorporates an interdigitated microelectrode (IDE) array comprising on-chip working, counter, and reference electrodes. Glucose oxidase and lactate oxidase were immobilized in a platinum black/o-phenylenediamine/β-cyclodextrin polymer matrix on two separate working electrodes. For glucose sensing, an effective in-situ pH control method enabled by the IDEs was employed to optimize the pH for accurate detection. Both sensors demonstrated detection over a range of 0.05–2 mM with excellent linearity (R² ~ 0.99). COMSOL simulations and interference studies were conducted to evaluate the sensors potential for application in saliva.

Downscaling of metal interconnects has become a bottleneck in the back-end-of-line processing of CMOS semiconductor devices. The conductivity of the commonly used Cu metal drastically reduces at nanoscale, limiting its use as the devices shrink, as the metal starts forming non-conductive islands. This has led to the requirement for new interconnect metals such as Co and Ru, as they have a much higher tendency to form conductive films with horizontal growth at nanoscale. Understanding how the morphology of interconnects depends on the metals’ atomistic properties and their interactions at diffusion barrier layers is necessary to continue the rapid development of interconnects. In this study we have used first principles density functional theory (DFT) relaxations, ab initio molecular dynamics (aiMD) and neural network machine learning potentials (MLP) to investigate how the morphology of Cu, Co, and Ru differs on TaN substrates. We investigate the binding of single metal atoms and four atom clusters to obtain the metals’ substrate binding energy and metal-metal interaction energies. The morphology of the metals was then investigated by 15 ps molecular dynamics simulations with DFT and 5 ns with MLP potentials using larger metal structures that can display 2D and 3D morphologies. Comparing the binding energies with the obtained morphology allows us to demonstrate how the balance of metal-substrate and metal-metal interactions determines the morphology, while the MLP simulations allow longer timescale processes to be included. These insights help in the development of morphology predictors allowing a rapid method for screening new interconnect materials with targeted horizontal growth on substrates used in semiconductors.

Fetal pulse oximetry may improve intrapartum fetal evaluation by providing a non-invasive measurement of fetal oxygen saturation (FSpo2). To assess the association between abnormal intrapartum FSpo2 and perinatal and long-term neurodevelopmental outcomes, and to evaluate if the addition of the measurement of FSpo2 to established forms of fetal monitoring, such as fetal heart rate monitoring, affects birth, perinatal, and long-term neurodevelopmental outcomes. We conducted a comprehensive search of PubMed, EMBASE, CINAHL, The Cochrane Library, Web of Science, ClinicalTrials.gov, and WHO ICTRP from database inception through February 2024, with no restrictions on date, geographic region, country income level, or language. Studies involving women in labor with a cephalic baby were included. Two interventions were reviewed: (1) low FSpo2 (<30%), and (2) the use of fetal pulse oximetry during labor. Independent reviewers screened studies, extracted data, and assessed quality using the Risk of Bias tool and the Newcastle-Ottawa Scale. The approach evaluated evidence certainty. A random-effects meta-analysis followed PRISMA and MOOSE guidelines. Forty-seven studies with 13 071 mother-infant pairs were included. FSpo2 <30% was associated with umbilical artery pH <7.15 (odds ratio [OR] 7.86, 95% confidence interval [CI] 3.29-18.75, I2 = 71%, P < 0.001), 5-min Apgar score less than 7 (OR 16.63, 95% CI 5.64-49.01, I2 = 30%, P < 0.001) and NICU admission (OR 5.89, 95% CI 1.73-20.01, I2 = 0%, P < 0.005). FSpo2 monitoring combined with fetal heart rate monitoring was associated with lower odds of cesarean section for non-reassuring fetal status (OR 0.59, 95% CI 0.40-0.86, I2 = 71%, P = 0.006) without impacting 5-min Apgar scores <7 (OR 0.66, 95% CI 0.37-1.17, I2 = 0%, P = 0.160) or neonatal intensive care unit admissions (OR 0.98, 95% CI 0.82-1.18, I2 = 0%, P = 0.840). FSpo2 monitoring combined with fetal heart rate monitoring may reduce unnecessary cesarean sections for suspected fetal distress without affecting short-term neonatal outcomes. The association between FSpo2 <30% and adverse perinatal outcomes supports its potential as a valuable adjunct in intrapartum monitoring.

A simple, fast, and robust technique for estimating waveguide loss is presented using the scattered light imaging from swapped input-output ports at different wavelengths. The propagation loss is determined by normalizing waveguide output-to-input intensity ratios, making the method insensitive to optical fiber-to-waveguide coupling efficiency. And the spatial variation effects along the waveguide length are mitigated by focusing on relative loss values. The approach is demonstrated on SU8 based multimode waveguides, including both straight and S-bend configurations with 5 mm radius of curvature and bend angles of 15°, 18°, 20° and 25°. The measured losses for these waveguides are (−17,−18,−20,−21,−25 dB/cm at 450 nm,(−19,−22,−24,−27,−33 dB / cm) at 526 nm, and (−9,−11,−14,−14,−24 dB /cm) at 635 nm respectively.