Search Results (302)

The escalating demand for miniaturization in electronics necessitates advanced laser micromachining for precise micro-via fabrication in PTFE-based PCBs. This study addresses challenges in controlling CO₂ laser kerf depth in PTFE, a material known for properties that complicate material removal. Employing a two-level full factorial Design of Experiments, the effects of number of loops, aperture, and pulse duration were systematically investigated. This analysis revealed that while pulse duration statistically impacted ablation depth, the number of loops was operationally most critical due to its direct proportionality with kerf depth in PTFE, leveraging its low thermal conductivity. Aperture, defining the laser spot size, was often constrained by PCB geometric specifications. The predictive models developed demonstrated robust generalizability across different PTFE-based laminates. Validation of the production of PCBs achieved a 100% success rate in meeting geometric tolerances and surface integrity. This DoE-based framework establishes a process window, significantly reducing parameter identification time and scrap, thereby enhancing manufacturing yield. Full article

This study developed predictive mathematical models for UV laser penetration depth in FR-4-based rigid–flex printed circuit boards, addressing the critical need for precise material removal in applications like protective plug removal. Utilizing a comprehensive Design of Experiments framework, specifically two-level full factorial designs, the influence of key operational parameters—number of loops, scanning speed, and focal position offset—on material removal was systematically investigated in both laminate and multilayer substrates. Empirical models were established for both substrate types, identifying significant factors and interactions that govern penetration depth with physical justification. Comparative analysis revealed that the multilayer model consistently predicted deeper penetration (6–17 µm) than the laminate model under identical conditions, primarily due to reduced heat-associated phenomena with prepreg, yet the laminate model offered a reasonable approximation for complex stack-ups. Rigorous validation through confirmation experiments, achieving 100% success in electrical integrity tests with compliant plug removal, unequivocally demonstrated the models’ robustness and reliability. This research provided a crucial tool for optimizing UV laser micromachining processes, significantly reducing parameter identification times and minimizing scrap generation, thereby enhancing the efficiency and reliability of advanced rigid–flex PCB manufacturing. Full article

A robust and cost-effective fiber-optic ultrasound sensor based on a slope-symmetric Fabry–Perot interferometer (FPI) is presented, employing dual-channel quadrature-biased heterodyne interrogation with an acousto-optic modulator (AOM). By introducing a 200 MHz frequency shift that yields an effective π/2 phase offset between the direct (unshifted) and frequency-shifted optical paths, the system ensures complementary sensitivity: when one channel operates at zero slope on the FPI transfer function (minimum sensitivity), the other resides at maximum slope, providing inherent immunity to laser wavelength drift and environmental perturbations. Experimental validation demonstrates reliable ultrasound detection across varying operating points. At quadrature extremes, one channel achieves peak amplitudes of ±2 V while the other is quiescent, whereas intermediate points enable simultaneous detection with amplitudes of ±1.5 V (AOM channel) and ±0.05–0.1 V (direct channel), accompanied by corresponding DC levels ranging from ~0.4 V to 1.6 V. The AOM channel utilizes simple envelope detection after 9.5–11.5 MHz bandpass filtering, maintaining low cost, though coherent mixing is suggested for enhanced weak-signal performance. The angle-symmetric FPI design, combined with gold-disk reflector adaptations and potential femtosecond laser micromachining, further reduces fabrication costs without sacrificing finesse or sensitivity. This quadrature-biased approach offers superior stability compared to single-channel systems, making it highly suitable for practical applications in photoacoustic imaging, nondestructive testing, and structural health monitoring. Full article

Laser-based manufacturing processes—including marking, hardening, cutting, and welding—demand the precise selection of processing parameters, as the resulting surface state is critically dependent on the delivered power density and beam–material interaction time. This study presents a unified predictive framework for estimating the critical surface power density thresholds for melting q_scm and evaporation q_scv as functions of scanning speed v for the following four technologically important metallic materials: titanium, C26000 brass, SS304 stainless steel, and 42CrMo4 alloy steel. The principal novelty of this work is twofold. First, it provides the first directly comparative analysis of these four materials under identical, standardized laser conditions (λ = 1064 nm, d = 40 μm, constant absorptivity A = 0.4), eliminating the confounding effects of variable beam geometries and optical assumptions that hinder cross-study comparisons. Second, it translates fundamental thermophysical principles into a practical engineering tool, such as a validated spreadsheet calculator that outputs material-specific threshold curves in real time, enabling rapid, physics-based parameter estimation without recourse to complex numerical simulations. The computed threshold curves exhibit a consistent non-linear increase with scanning speed for all materials, governed by the inverse relationship between interaction time and required power density. The following clear material hierarchy emerges: C26000 brass exhibits the highest thresholds (e.g., q_scm = 0.94 × 10¹⁰ W/m², q_scv = 10.74 × 10¹⁰ W/m² at v = 100 mm/s) due to its high thermal conductivity, while titanium shows the lowest (q_scm = 0.19 × 10¹⁰ W/m², q_scv = 0.48 × 10¹⁰ W/m² at v = 100 mm/s) as a consequence of strong heat confinement. SS304 and 42CrMo4 occupy intermediate positions, with 42CrMo4 demonstrating notably higher evaporation resistance than SS304 despite similar melting thresholds. The resulting dual-threshold framework delineates three distinct process regimes—sub-melting heating, melting-dominant processing, and evaporation—providing a quantitative basis for parameter selection in applications ranging from surface hardening to micromachining. By bridging the gap between theoretical material science and applied manufacturing, this work offers a robust, first-order reference for process design and establishes a methodological template for future comparative studies of laser–material interactions. Full article

The technology development for the mass ceramic gas flow sensor (CGFS) adopted for harsh operating conditions is presented. The main characteristic of this technology is its simplicity and affordability for mass fast prototyping of CGFS with a limited set of technological equipment. Special attention is paid to the discussion of the technological and operational materials’ compatibility, flexibility, and speed of their processing to adapt the best mass flow sensor design option. The CGFS, designed and manufactured in just a few days, was tested in conditions close to the real ones and demonstrated the ability to measure gas flow in the range from 0.21 m/s to 1.25 m/s, with a constant power consumption of 152 mW@346 °C. Full article

This work presents, to the best of our knowledge, the first experimental report of an erbium/ytterbium double-clad ring fiber laser based on nonlinear polarization rotation (NPR) operating in a self-starting Q-switched high-order harmonic mode locking noise-like pulse (QHML-NLP) regime. The NPR mechanism relies on an arrangement composed of a beam splitter cube, a half-wave retarder, and a quarter-wave retarder. Through specific adjustments of the wave retarders and pump power, the laser cavity engages the QHML-NLP regime, where mode-locked burst-like pulses containing a significant number of NLPs are modulated by a giant Q-switched envelope. The laser system emits at the 132nd-order harmonic mode locking (HML) frequency, representing the highest order achieved to date in the framework of QHML-NLP. Additional features include a broadband optical spectrum with dual-wavelength emission at 1568.4 nm and 1605.9 nm, and maximum energies of 2.37 µJ for the Q-switched envelope and 200 nJ for the mode-locked burst-like pulse. These detailed experimental results reveal remarkable aspects in the NLP dynamics, contributing to a deeper understanding of their physical mechanisms and highlighting their potential as novel laser sources for micromachining and nonlinear optics. Full article

The development of photonic-integrated circuits (PICs) for data communication, sensing, and quantum computing is hindered by the high complexity and cost of traditional fabrication methods, which rely on expensive equipment, limiting accessibility for research and prototyping. This study introduces a Direct Laser Writing (DLW) system designed as a low-cost alternative, utilizing an XY platform for precise substrate movement and an optical system comprising a collimator and lens to focus the laser beam. Operating on a single layer, the system employs SU-8 photoresist to fabricate polymer-based structures on substrates such as ITO-covered glass. Preparation involves thorough cleaning, spin coating with photoresist, and pre- and post-baking to ensure material stability. This approach reduces dependence on costly infrastructure, making it suitable for academic settings and enabling rapid prototyping. A user interface and custom slicer process standard .dxf files into executable commands, enhancing operational flexibility. Experimental results demonstrate a resolution of 10 µm, with successful patterning of structures, including diffraction grids, waveguides, and multimode interference devices. This system aims to transform PIC prototype fabrication into a cost-effective, accessible process. Full article

This work presents the design, fabrication, and characterization of a three-dimensional FeCo-based flux-modulator microwinding intended for integration into high-torque axial-flux Vernier micromotors. The proposed micromotor architecture modulates the stator magnetic flux using 12 magnetically isolated FeCo teeth interacting with an 11-pole permanent-magnet rotor. The design requires the manufacturing of complex three-dimensional micrometric parts, including three teeth and a cylindrical core. Such a complex design cannot be manufactured using conventional micromanufacturing lithography or 2D planar methods. The flux-modulator envelope dimensions are 250 μm outer diameter and 355 μm height. It is manufactured using a femtosecond laser-machining process that preserves factory-finished surfaces and minimizes heat-affected zones. In addition, this micrometric part has been wound using 20 μm diameter enamelled copper wire. A dedicated magnetic clamping fixture is developed to enable multilayer microwinding of the integrated core, producing a 17-turn inductor with a 60.6% fill factor—the highest reported for a manually wound ferromagnetic-core microcoil of this scale. Geometric and magnetic characterization validates the simulation model and demonstrates the field distribution inside the isolated core. The results establish a viable micromanufacturing workflow for complex 3D FeCo microwindings, supporting the development of next-generation high-performance MEMS micromotors. Full article

Thermocatalytic sensors are used as universal explosion meters for measurement of the Lower Explosive Limit (LEL) of hydrocarbon gases mixtures. Historically, thermo-catalytic sensors, with their bulky “pellistor” design, have been poorly suited for mass production using group microelectronic processing. Another significant challenge for developers of new sensor designs is to minimize power dissipation while enhancing the service life and resistance of catalytic elements to poisoning from silicon–organic and sulfur-containing gases. To meet the specified requirements, we developed a low-power thermocatalytic sensor utilizing ceramic technology, capable of holding the temperature of technology operations up to 900 °C. Full article

A reflective in-fiber liquid microsphere whispering gallery mode (WGM) resonator based on a Y-waveguide coupler is proposed and experimentally demonstrated. The sphere resonator is introduced inside a single-mode fiber (SMF) by using femtosecond laser micromachining and fusion splicing. A Y-waveguide coupler is fabricated with femtosecond laser direct writing, which is used to simultaneously excite and collect the WGM field through evanescent field coupling. High-index liquids are filled into the sphere through a laser-drilled channel to form a liquid microsphere where the WGM resonation takes place. The WGM resonator is sensitive to the refractive index (RI) of the filled liquids, and a RI sensitivity of 439 nm/RIU is achieved in an index range from 1.672 to 1.692. The liquid microsphere resonator is also sensitive to temperature, with a sensitivity of −307.1 pm/°C obtained. The microsphere resonator is small in size and robust, which has broad application prospects in the field of food and the chemical industry. Full article

Surface functionalisation of polymers is essential for enhancing properties such as wettability and mechanical resistance. This study presents a scalable, coating-free approach to fabricate hydrophobic and superhydrophobic Polydimethylsiloxane (PDMS) surfaces. Aluminium (AA2024) moulds were microstructured using a TruMicro femtosecond laser system to generate grid patterns with controlled hatch distances and depths, as well as laser-induced periodic surface structures (LIPSSs). These features were accurately replicated onto PDMS, as confirmed by scanning electron miscoscopy (SEM) and profilometry. Contact angle measurements showed a marked increase in hydrophobicity, reaching superhydrophobicity for optimised parameters, with surface stability maintained over four months without degradation. Full article

Microchannel reactors are among the most important tools used for high-performance continuous-flow synthesis. However, most microchannel reactors manufactured with conventional micromachining techniques are limited to two-dimensional (2D) planar geometries, which pose significant challenges for the custom production of three-dimensional (3D) architectures that offer superior microchemical performance. Using unique nonlinear optical effects of ultrafast lasers, hollow microchannel structures with 3D configurations can be flexibly created within transparent glass materials through either direct removal or subsequent chemical etching methods. This review provides an overview of typical fabrication techniques for 3D glass microchannel reactors based on ultrafast laser microfabrication, as well as their state-of-the-art advancements, including large-scale and high-precision manufacture of all-glass microchannels and the facile integration of online monitoring modules. Moreover, the applications of these fabricated microchannel reactors for various continuous-flow microchemical reactions are introduced. Ultrafast laser-enabled 3D glass microchannel reactors hold great potential for developing innovative and industrial-scale continuous-flow manufacturing processes in chemical engineering and pharmaceutical production. Full article

Structure-Modulated Long-Period Fiber Gratings (SM-LPFGs) represent an advancement in fiber optic sensor technology, moving beyond traditional photosensitivity-based fabrication to achieve enhanced performance through the direct physical modification of the geometry of the fiber. This review provides a comprehensive analysis of the primary fabrication techniques enabling this approach, including CO₂ laser inscription, femtosecond laser micromachining, electric-arc discharge, chemical etching, and fusion tapering. The central focus of this work is the elucidation of the definitive structure–performance relationship, systematically detailing how engineered geometries such as helical profiles, micro-tapers, and asymmetric grooves unlock novel sensing capabilities. We demonstrate how these specific structures are strategically designed to induce circular birefringence for torsion measurement, enhance evanescent field interaction for ultra-sensitive refractive index detection, and create localized stress concentrations for high-resolution strain and vector bending sensing. Furthermore, the review surveys the practical implementation of these sensors in critical application domains, including structural health monitoring, biomedical diagnostics, and environmental sensing. Finally, we conclude by summarizing key achievements and identifying promising future research directions, such as the development of hybrid fabrication processes, the integration of machine learning for advanced signal demodulation, and the path towards industrial-scale production. Full article

This paper introduces a versatile approach to achieve specific surface functionality with-out the need for detailed knowledge of surface topography. This is accomplished for applications targeting wettability properties by integrating contact angle measurement into a micromachining setup with a nanosecond pulsed UV laser, allowing for fully automated programs to find optimal functionalization without requiring knowledge on the topography or on possible laser-induced chemical changes itself. This study investigates the impact of various processing parameters, including laser pulse energy, scanning speed, hatching distance, jump speed, and laser repetition rate, on the wetting properties of two widely used polymers: polyethylene (PE) and ethylene propylene diene monomer (EPDM). A design of experiment (DOE) approach is used for experimental design and subsequent modeling. Finally, the effectiveness of this new approach is evaluated and compared with conventional methods. Full article

In this paper, we propose and experimentally demonstrate a dual-parameter fiber optic sensor, which combines a Fabry–Perot interferometer (FPI) and a Mach–Zehnder interferometer (MZI) for simultaneous pressure and temperature sensing. The Fabry–Perot (FP) cavity is formed by sandwiching a capillary fiber between a single-mode fiber and a dual-core fiber (DCF). A fluid channel is very close to the central core of the DCF. By precisely drilling micro-air chambers in the annular cladding of a capillary fiber (CF) using a femtosecond laser, external air pressure can directly affect the capillary fiber and induce changes in the refractive index of the air in the CF. The F-P cavity achieves a pressure sensitivity of 3.67 nm/MPa with a temperature cross-sensitivity of 2.82 pm/°C. The MZI is constructed using a dual-core fiber filled with silicone oil in the fluidic channel, which enhances temperature sensitivity through the thermo-optic effect. The MZI sensor exhibits a nonlinear temperature response with an average sensitivity of 103.43 pm/°C. The corresponding pressure cross-sensitivity is about –0.11 nm/MPa. Due to very low cross-sensitivity, simultaneous measurement of temperature and gas pressure is feasible. In addition, we implement a variant by replacing silicone oil with a UV-curable adhesive, which delivers a comparable FP-based pressure sensitivity of ~3.93 nm/MPa while yielding an MZI-based temperature sensitivity of 71.7 pm/°C and potentially improved long-term stability. Full article