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Researchers have proposed diverse techniques for fabricating saturable absorbers, including aqueous acid exfoliation, evanescent coupling, and electrochemical exfoliation, with fabrication complexity and limitations that reduce saturable absorber performance and application range. We describe mechanical exfoliation and transfer as an efficient and straightforward mechanism for a MAX phase nanomaterial, V2ZnC, expelled into a 48.926 µm thin saturable absorber film for passively Q-switched and mode-locked all-fibre lasers, exhibiting a modulation depth of 13.16%, non-saturable absorption to be 10.21%, and saturation intensity of 4.32 kW/cm2 MAX-SA; all of which demonstrated its superiority with a self-starting laser. The output laser was stable with a pulse width of 7.160 µs and a repetition rate of up to 62.23 kHz at a threshold pump power of 59.53 mW in Q-switched conditions and 346.8 ns pulse width with 963.3 kHz repetition rate at a pump power of 80.41 mW in mode-locked conditions. It is a excellent saturable absorber for the use of pulse laser production in all-fibre laser cavities because of its simple manufacturing process and outstanding optical, physical, thermal, and mechanical qualities. [ABSTRACT FROM AUTHOR]

Gold–titanium oxide nanocomposites (Au–TiO2 NCPs) were fabricated through pulsed laser-induced photolysis (PIPS) and verified to be usable for the visible light catalytic degradation of methylene blue (MB). The PIPS method can produce a sufficient amount of NCPs quickly and has potential to be commercialized. In contrast to other studies, we clarified the optical spectrum of the light sources, including peak power, bandwidth, and total intensity used for photodegradation reactions and discovered that the photodegradation efficiency of the produced Au–TiO2 NCPs in the wavelength range of 405 nm could reach 37% in 30 min due to the charge transfer between Au and TiO2. The control experiment shows that the addition of individual Au and TiO2 nanoparticles (NPs) to an MB solution has no enhancement of degradation ability under visible light illumination. The photodegradation of Au–TiO2 NCPs can be further improved by increasing the concentrations of auric acid and TiO2 NPs in a precursor under PIPS fabrication. [ABSTRACT FROM AUTHOR]

By scanning the charge-deposition profile produced by a pulsed laser throughout a device, the spatially dependent charge-collection efficiency (CCE) can be determined. This is demonstrated by extracting the depth-dependent CCE in two photodiodes. The resulting collection efficiency curves are found to be consistent with their device structures and the expected charge-collection mechanisms. By applying the efficiency curves to the charge-deposition curves for both heavy ions and pulsed X-rays, the calculated collected charge values show very good agreement with experimental results. This suggests that the profiles extracted using the laser can help predict charge-collection data from other excitation sources and could improve modeling efforts by determining sensitive volumes. [ABSTRACT FROM AUTHOR]

A novel approach for two-photon absorption (TPA) pulsed-laser testing produces extended charge deposition profiles that are analogous to those produced by heavy ions. In this approach, which utilizes an axicon rather than a spherical lens, the conventional Gaussian beam is replaced by a quasi-Bessel beam. The key feature of a quasi-Bessel beam, relevant to pulsed-laser single-event effects (PL-SEE) studies, is that its radial size (1~μm) remains constant over the axial length of the beam (several 100 s of μm) resulting in a charge-deposition profile that more closely mimics that produced by a heavy ion. This elongated charge distribution directly lends itself to a simple and intuitive description in terms of linear-energy transfer (LET), facilitating laser/ion correlation studies. Experimental results comparing a conventional TPA PL-SEE focusing geometry and the axicon focusing geometry are presented for three different test vehicles: a 45-nm silicon-on-insulator (SOI) nFET, a bulk silicon photodiode, and an LM124 operational amplifier. By using the axicon approach, strong laser/ion correlation is observed in the silicon photodiode for single-event transients (SET) across a wide range of LETs. The correlation is achieved by “tuning” the laser to the desired LET rather than relying on preexisting heavy-ion data, and therefore, this approach holds promise as a predictive tool. [ABSTRACT FROM AUTHOR]

This study developed a model involving the energy balance and decomposition at the ablated interface due to the heat transport, optical decomposition and activation energy in Acrylonitrile Butadiene Styrene/PolyVinyl Chloride (ABS/PVC). The prediction for ablation depth obtained from this study is compared with the available experimental data. The predicted results agree with the measured data. The effects of laser processing parameters, optical and thermal properties of ABS/PVC on the variation of the laser-ablated depth with the laser fluences are also discussed. The results validate that the pulsed-laser ablation rate at the initial short period is dominated by optical penetration absorption for laser and is linearly proportional to the logarithm of the laser fluence by a ratio factor "optical absorption length" (i.e., the ablation rate follows Beer's law at the initial short period). [ABSTRACT FROM AUTHOR]

Remote-controlled, non-destructive testing is necessary to detect corrosion of the reinforced concrete structures at the Fukushima Daiichi Nuclear Power Plant (NPP) de-commissioning site. This work aims to demonstrate that laser-induced ultrasonic guided wave technology can be applied to achieve this task. Hence, accelerated electrolytic corrosion is performed on a reinforced concrete specimen fabricated by embedding a steel rod into mortar. Waveforms of the laser-induced ultrasonic guided wave on the rod are measured with a previously employed piezoelectric transducer (PZT) probe, for each fixed corrosion time. Based on the results of Fourier and wavelet transforms of the waveforms, issues concerning the detection and extent of rebar corrosion are discussed. It is exhibited that the changes in bonding strength due to corrosion are distinguishable in the frequency domain of the ultrasonic signal. [ABSTRACT FROM AUTHOR]

Remote-controlled, non-destructive testing is necessary to detect corrosion of the reinforced concrete structures at the Fukushima Daiichi Nuclear Power Plant (NPP) de-commissioning site. This work aims to demonstrate that laser-induced ultrasonic guided wave technology can be applied to achieve this task. Hence, accelerated electrolytic corrosion is performed on a reinforced concrete specimen fabricated by embedding a steel rod into mortar. Waveforms of the laser-induced ultrasonic guided wave on the rod are measured with a previously employed piezoelectric transducer (PZT) probe, for each fixed corrosion time. Based on the results of Fourier and wavelet transforms of the waveforms, issues concerning the detection and extent of rebar corrosion are discussed. It is exhibited that the changes in bonding strength due to corrosion are distinguishable in the frequency domain of the ultrasonic signal.

The multi-dimensional ultrasonic-assisted pulsed-laser surface irradiation method was introduced to relieve the residual stress in the AISI 1045 steel specimen based on the Nd:YAG pulsed-laser machine. In this stress relief process, the acoustic energy was imposed into the AISI 1045 steel specimen accompanied by the pulsed-laser surface irradiation, which could be called as the multi-dimensional ultrasonic-assisted stress relief (MDUASR). The mechanism of the MDUASR was discussed based on the thermal activation theory. In addition, the experiments for the MDUASR and the multi-dimensional ultrasonic stress relief (MDUSR) were carried out to validate the residual stress relieving effect and the energy-saving effect of the MDUASR. The results show that the MDUASR has good effect on relieving residual stress and the MDUASR can reduce the energy consumption compared with the MDUSR. Furthermore, the mechanism of the MDUASR can be attributed to the metal softening effect and the dynamic stress effect. The findings confirm that the thermal energy induced by pulsed-laser surface irradiation can be adequately utilized to enhance the metal plasticity, which results in that the residual stress relieving effect of the MDUASR can be improved compared with the MDUSR. It can be concluded that the MDUASR belongs to an energy-saving and green environmental protection technology during the manufacturing process. [ABSTRACT FROM AUTHOR]

The high-energy oscillating electric current pulse (ECP) technology was introduced to relieve the residual stresses in the small AISI 1045 steel specimens treated by the pulsed-laser surface irradiation. The high-energy oscillating ECP stress relief experiments were conducted to study the effectiveness of the high-energy oscillating ECP technology. In addition, the electroplasticity framework was developed based on the thermal activation theory to reveal the mechanism of the high-energy oscillating ECP stress relief. The results show that the high-energy oscillating ECP stress relief has good effects on eliminating the residual stress. Furthermore, the residual stress relieving mechanism of the high-energy oscillating ECP stress relief can be attributed to the electric softening effect and the dynamic stress effect. The findings confirm that the significant effects of high-energy oscillating ECP on metal plasticity and provide a basis to understand the underlying mechanism of the high-energy oscillating ECP stress relief. [ABSTRACT FROM PUBLISHER]

Silicon-germanium heterojunction bipolar transistor (SiGe HBT) models are used in technology computer aided design (TCAD) to investigate single event transients induced by heavy-ion broadbeam and pulsed-laser two-photon absorption sources. A comparison between transient waveforms is provided, the proper extraction of heavy-ion broadbeam transients is discussed (along with circuit implications), and basic laser strike profiles are implemented in TCAD to provide insight into future design practices for simulation software to be used to describe laser-induced upsets in terms of an effective linear energy transfer (LET). [ABSTRACT FROM PUBLISHER]

The ultrasonic vibration method was introduced to relieve the residual stress in the small AISI 1045 steel specimen subjected to the pulsed-laser surface irradiation. The ultrasonic vibration plasticity framework was developed based on the thermal activation theory and the dislocation glide kinetics theory in order to reveal the double dynamic stress effect and the time effect of the ultrasonic stress relief. To validate the proposed model, the ultrasonic stress relief experiments were carried out using the AISI 1045 steel specimens treated by the pulsed-laser surface irradiation based on the Nd:YAG pulsed-laser machine. The results show that the ultrasonic stress relief has good effects on eliminating residual stress. Furthermore, the residual stress relaxation due to the double dynamic stress effect can be improved by increasing the ultrasonic vibration power and the initial magnitude of residual stress. The residual stress decrease due to the time effect can be improved by increasing the ultrasonic vibration time. The unified ultrasonic vibration plasticity model can accurately account the double dynamic stress effect and the time effect. The findings confirm that the ultrasonic stress relief can be used to eliminate residual stress in small workpieces and provide a basis to understand the underlying mechanism of the ultrasonic stress relief. [ABSTRACT FROM AUTHOR]

Single-event transient (SET)-hardened SiGe HBT RF single-pole single-throw (SPST) switches were designed and fabricated for the first time. TCAD-based heavy-ion simulations and two-photon absorption (TPA) laser-induced beam experiments were used to optimize the switch core configuration for SET mitigation. Among different configurations, the reverse-connected series and shunt device core, where both emitter terminals are connected to the output, exhibits the smallest transient peaks and shortest durations at the output terminal of the switch. Based on this finding, the design considerations for maximizing the RF performance of SiGe HBT SPST RF switches are discussed. In addition, a comparison of the SET response and RF performance of CMOS (nFET) SPST and SiGe HBT SPST switches provides additional information on the trade-offs in the SET mitigation strategy and potential RF capabilities. [ABSTRACT FROM PUBLISHER]

A SiGe RF low-noise amplifier (LNA) with built-in tolerance to single-event transients is proposed. The LNA utilizes an inverse-mode SiGe HBT for the common-base transistor in a cascode core. This new cascode configuration exhibits reduced transient peaks and shorter transient durations compared to the conventional cascode one. The improved SET response was verified with through-wafer two-photon absorption pulsed-laser experiments and supported via mixed-mode TCAD simulations. In addition, analysis of the RF performance and the reliability issues associated with the inverse-mode operation further suggests this new cascode structure can be a strong contender for space-based applications. The LNA with the inverse-mode-based cascode core was fabricated in a 130 nm SiGe BiCMOS platform and has similar RF performance to the conventional schematic-based LNA, further validating the proposed approach. [ABSTRACT FROM PUBLISHER]

Abstract: The atmospheric corrosion test and residual stress measurement were performed to evaluate the effect of laser irradiation on stress corrosion cracking (SCC) initiation. Second-harmonic Nd:YAG laser pulses (pulse width: 10ns) were irradiated on a type-304L stainless-steel plate. The specimens were placed in a chamber at 353K with RH=35% for the corrosion test. When laser energies were 30 and 300mJ, cracks caused by SCC or pitting were observed on the surface of the specimens. The cracks were classified into two types on the basis of cumulative probability distribution; one of the types is related to the laser irradiation condition. The mean maximum crack depths were about 27 and 52μm when laser energies were 30 and 300mJ, respectively. These values were the same as the depth at which the tensile residual stress was induced from the surface of the specimen by laser irradiation. These results suggest that the maximum stress corrosion crack depth was caused by the tensile residual stress induced by laser irradiation, and that the crack stopped propagating when the crack depth was larger than several dozen μm in this test set. When laser pulses of 300mJ energy were irradiated on the surface of the specimen by shot peening, the tensile stress was induced up to 20μm from the surface, and the compressive stress was observed at a larger depth. These results show that the laser irradiation is less effective in obtaining tensile residual stress of the specimen compared to when laser pulses are irradiated on the specimen treated by shot peening. The depth of tensile stress obtained by laser irradiation is much shorter than that of compressive stress obtained by shot peening. [Copyright &y& Elsevier]

The objective of this study was to investigate the surface characteristics of an aluminum 6061-T6 alloy subjected to Nd:YAG pulsed-laser irradiation. The test specimens were prepared by a mechanical polishing process using diamond paste and emery polishing paper to obtain different levels of initial surface roughness. After ten pulsed-laser shots, the surface morphology was observed via optical microscopy (OM) and scanning electron microscopy (SEM). Nano-indentation hardness testing was also conducted on the irradiated surface. The diameter of the melted zone increased with surface roughness because of the multiple reflection and absorption of the laser beam. The relative absorbance was measured as a function of the diameter of the melted zone with varied surface roughness. [ABSTRACT FROM AUTHOR]

Abstract: The sorption and photocatalytic decolorization (under irradiation of monochromaticitic 355nm-pulsed-laser) behaviors of Rhodamine 6G (Rh 6G) in presence of BiOCl semiconductor in aqueous solution were studied in this paper. The sorption kinetic and isotherm behaviors of Rh 6G over BiOCl catalyst were investigated and discussed through pseudo-second-order/intraparticle diffusion models and Langmuir/Freundlich models, respectively. The effect of critical parameters such as catalyst dosage, initial concentration of Rh 6G, and laser pulse energy on the photocatalytic decolorization process was investigated. The photocatalytic decolorization and photonic efficiency of BiOCl was compared with standard catalyst (TiO2) and the obtained results were discussed in terms of their band edge position. Finally, the chemical stability of BiOCl photocatalyst was studied by measuring the X-ray diffraction (XRD) pattern of BiOCl samples after the reaction. [Copyright &y& Elsevier]

The present work describes the novel, relatively simple, and efficient technique of pulsed laser deposition for rapid prototyping of thin films and multi-layer heterostructures of wide band gap semiconductors and related materials. In this method, a KrF pulsed excimer laser is used for ablation of polycrystalline, stoichiometric targets of wide band gap materials. Upon laser absorption by the target surface, a strong plasm a plume is produced which then condenses onto the substrate, kept at a suitable distance from the target surface. We have optimized the processing parameters such as laser fluence, substrate temperature, background gas pressure, target to substrate distance, and pulse repetition rate for the growth of high quality crstalline thin films and heterostructures. The films have been characterized by x-ray diffraction, Rutherford backscattering and ion channeling spectrometry, high resolution transmission electron microscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy, cathodoluminescence, and electrical transport measurements. We show that high quality AlN and GaN thin films can be grown by pulsed laser deposition at relatively lower substrate temperatures (750–800°C) than those employed in metal organic chemical vapor deposition (MOCVD), (1000–1100°C), an alternative growth method. The pulsed laser deposited GaN films (∼0.5 µm thick), grown on AlN buffered sapphire (0001), shows an x-ray diffraction rocking curve full width at half maximum (FWHM) of 5–7 arc-min. The ion channeling minimum yield in the surface region for AlN and GaN is ∼3%, indicating a high degree of crystallinity. The optical band gap for AlN and GaN is found to be 6.2 and 3.4 eV, respectively. These epitaxial films are shiny, and the surface root mean square roughness is ∼5–15 nm. The electrical resistivity of the GaN films is in the range of 10−2–102 Θ-cm with a mobility in excess of 80 cm2V−1s−1 and a carrier concentration of 1017–1019 cm−3, depending upon the buffer layers and growth conditions. We have also demonstrated the application of the pulsed laser deposition technique for integration of technologically important materials with the III–V nitrides. The examples include pulsed laser deposition of ZnO/GaN heterostructures for UV-blue lasers and epitaxial growth of TiN on GaN and SiC for low resistance ohmic contact metallization. Employing the pulsed laser, we also demonstrate a dry etching process for GaN and AlN films. [ABSTRACT FROM AUTHOR]

Myopia, diabetes, and aging are the main causes of progressive vitreous collagen aggregation, resulting in vitreous opacities, which can significantly disturb vision. As vitreous opacities, which induce the visual phenomenon of "floaters", are accessible with nanomaterials and light, we propose a nanotechnology-based approach to locally ablate them with highly reduced light energy compared to the more traditional YAG laser therapy. Our strategy relies on the plasmon properties of gold nanoparticles that generate vapor nanobubbles upon pulsed-laser illumination whose mechanical force can ablate vitreous opacities. We designed gold nanoparticles coated with hyaluronic acid (HA), which have excellent diffusional mobility in human vitreous, an essential requirement to reach the vitreous opacities. In addition, we found that HA-coated gold nanoparticles can accumulate extensively on human vitreous opacities that were obtained by vitrectomy from patients with vision-degrading myodesopsia. When subsequently applying nanosecond laser pulses, the collagen aggregates were efficiently destroyed with ∼1000 times less light energy than typically used in YAG laser therapy. This low-energy "floater-specific destruction", which is due to the accumulation of the small gold nanoparticles on the opacities, is attractive, as it may be safer to the surrounding ocular tissues while at the same time being easier and faster to apply compared to YAG laser therapy, where the opacities need to be ablated piece by piece by a tightly focused laser beam. Gold nanoparticle-assisted photoablation may therefore provide a safer, faster, and more reliable destruction of vitreous opacities in the treatment of ophthalmologic diseases.