Threshold Laser Energy Research Articles

A Single Event Upset Resilient Latch Design with Single Node Upset Immunity

In this paper, a latch design with single node immunity to single event upsets during the hold state is proposed. This structure is based on the original Quatro latch and have two more redundant storage nodes. Compared with the reference, this structure is able to recover if any of these nodes is struck by ion particles during the hold state and it also has improved multiple node upset performance. Simulations and laser experiment results have validated its effectiveness of SEU resilience by having a larger laser energy threshold for upset and lower SEU error counts compared with the reference. The power, area, and delay penalties are 86%, 48%, and 64% respectively; they are as a consequence of six more transistors added to the latch.

Influence of Preheating on the Microstructure Evolution of Laser Re-Melting Thermal Barrier Coatings/Ni-Based Single Crystal Superalloy Multilayer System.

Laser surface re-melting (LSR) is a well-known method to improve the properties of atmospheric plasma-spraying thermal barrier coatings (APS TBCs) by eliminating the voids, incompletely melted particles and layered-structure. Laser energy density should be carefully selected to reduce the exposed thermal damage of the underlying single crystal (SX) matrix. Therefore, the purpose of this paper was to identify the effect of introducing induction heating to laser modifying of APS TBCs coated on Ni-based SX superalloy. The results indicated that the preheating of the substrate can lower the laser energy threshold that is required for continuously re-melting the coating. It proved that, in LSR processing of a APS TBCs/ SX matrix multilayer system, the combined method of adopting the low laser energy and preheating at elevated temperature is an effective means of minimizing the cracking susceptibility of top ceramic coating, resulting from decreasing the mismatch strain between the re-melted layer and residual APS TBCs, which can significantly improve the segmented crack condition in terms of crack dimension and crack density. Moreover, this combined method can remarkably lower heat input into an SX matrix and correspondingly the interface stored energy induced by pulsed laser thermal shock, which can effectively lower the tendency for surface recrystallization after the subsequent heat treatment.

Random laser action in dye-doped xerogel with inhomogeneous TiO2 nanoparticles distribution

Rhodamine 6G-doped TEOS-derived xerogels containing different concentrations of TiO2 nanoparticles with average diameter of about 350 nm were designed to study random laser action. Due to the decantation of TiO2 nanoparticles during the sol–gel process, the obtained xerogels samples exhibits an inhomogeneous TiO2 distribution, with a higher concentration at one of the sample surfaces. By pumping the samples at each of the surfaces at a time with a ps-laser at 532 nm, differences in the emission behavior were observed. The higher concentration of TiO2 in one side of the sample, which occurs during its preparation, was shown to play an important role in the random laser energy threshold and emission spectra, depending on what side of the sample the excitation takes place. The difference in the laser threshold shows that the way scatterers are volumetrically distributed can increase or decrease the pump energy required for laser action.

SiGe BiCMOS线性器件脉冲激光单粒子瞬态效应研究

To verify the sensitivity of the single event transient effects of SiGe BiCMOS linear devices, a typical operational amplifier THS4304 and a voltage regulator TPS760 were selected to study the single event effects with pulsed laser. In the experiments, a method was proposed to determine the laser threshold energy of single event transient by gradual changing energy. And the sensitive region of single event effects within the device was analyzed by point-by-step scanning method. On this basis, the interaction between the pulse laser energy and the single event transient was analyzed, and the single event effects cross section was obtained, which provided a reference for the selection and application of the SiGe BiCMOS devices in the satellite electronic system and the design of the radiation hardening.

Kinetics of cell death triggered photothermally using folate-conjugated gold nanoparticles and various laser irradiation conditions in cancer cells

Introduction: In this study, we explore in detail cell-specific targeting efficacy of nano-photo-thermal therapy (NPTT) method and the resulting responses that are induced by variable laser intensities and exposure times in cancer cells to induce selective apoptosis. We delineate the synthesis of a high-yielding synthetic F-AuNPs by tailoring the surface of gold nanoparticles with folic acid to enhance cell selectivity and specificity. Materials and Methods: For this purpose, synthesized F-AuNPs treated cells were irradiated with various laser intensities and exposure duration. Both KB cancer cells, as a folate receptor over-expressing cell line, and L929 normal cells, with low level of folate receptors were used. Following various regimes of NPTT, Cytotoxicity was assessed by MTT assay and comparison of induced apoptosis and necrosis in population of cells were depicted by Annexin/PI staining. Results: We report no significant cytotoxicity difference between KB and L929 cell lines at concentrations up to 40 μM of F-AuNPs. Moreover, no significant cell lethality occurred for various laser irradiation conditions. However, in photothermal therapy, the viability of KB and L929 cells was 57% and 83%, respectively. Flow cytometry clearly revealed the kinetics of cell death. The majority of cancer cell death was related to apoptosis (41% apoptosis of 43% overall cell death). Conclusion: Together, these findings confirm that F-AuNPs based NPTT can either induces cell death via apoptosis or necrosis. The main factor determining whether a cell will die due to apoptosis or necrosis on-demand with PTT depends on laser heating level. Our main target must be to only trigger apoptosis during PTT by using suitable irradiation conditions. As a result, folate targeting ability of the F-AuNPs and laser energy threshold to induce selective apoptosis in cancer cells were shown.

CHANGE OF INDUCED STRESS WAVE ON COLLAGEN TISSUE FOR BIOSTIMULATION BY FREQUENCY-DOUBLED Nd:YAG LASER

In this research, thermoelastic effect was investigated for biostimulation without damage on the biological medium using laser. Thermoelastic effect was generated and mechanical stress was induced by laser irradiation on the collagen, the main protein in the human body, under various conditions with short pulsed laser. The threshold laser energy to induce stress wave in each medium thickness was examined with a piezo sensor. Based on the test, the stimulation strength can be controlled through the adjustment of medium thickness, laser energy and beam diameter. The result implies that precise stimulation with various strengths of stress waves can be generated at the target depth without direct contact with the biological medium. This research can be used valuably in various fields such as contactless biostimulation, low power laser treatment and laser haptic applications.

Plasma synthesis of nanodiamonds in ethanol

In this work, we examined the characteristics of the plasma formed by fs laser filamentation in ethanol that affected the nanodiamonds formation by optical emission spectroscopy. Molecular and atomic C species were detected in the plasma as the precursors to the nanodiamonds formed; above the threshold laser energy of 360 μJ. Thus, the generation of homogeneous nanodiamonds was identified to be occurred within laser energy of 360–550 μJ where atomic C, ionized C and C2 clusters coexisted. The process of fs laser filamentation is monitored with in-situ absorbance measurement of ethanol. The intensity of the absorbance peak of the sample at ∼228 nm, corresponds to intrinsic absorbance of diamond (σ→ σ* transition) was observed to increase with irradiation time. The prepared samples are characterized by using Raman spectroscopy, XPS and TEM. Nanodiamonds of <5 nm in size were produced. Photoluminescence measurements show that the sample fluoresce at ∼490 nm, when excited by 266 nm, 355 nm, 368 nm and 406 nm laser while additional photoluminescence peak is detected at 329 nm when excited by 266 nm laser.

Investigation of the surface morphology in glass scribing with a UV picosecond laser

This study reports the investigation of the morphology of the surface damaged during the laser scribing of glass and the analysis of the corresponding interaction mechanism between the laser and glass. In this study, the soda lime glass of 1.1 mm thick is scribed by an ultraviolet (UV) picosecond laser (Nd:YVO4) by varying laser power, scan speed and number of scans. From the analysis of experimental results, it is found that the surface morphology can be classified as three groups such as swelled surface, wave pattern (either shallow or deep) and groove depending on the accumulated laser energy per unit beam spot. The accumulation of the large laser energy (12–30 × 10−4 J) into the material induces volume meting and local vaporization below the surface without material removal, which makes bubbles inside glass volume and swelled surface through volume expansion. With the decrease of the energy accumulation (4.2–9 × 10−4 J), the surface morphology is changed into shallow wave pattern by slight material removal. With further decrease of the laser energy accumulation (1.4–3 × 10−4 J), either deep wave or groove morphology is obtained due to the increase of the material removal. Under very low laser energy accumulation region (0.3–1.05 × 10−4 J), the groove shape is only formed. In particular, the groove morphology without cracking is successfully produced within the range of 0.3–0.5 × 10−4 J. The threshold laser energy accumulation for surface damage is found to be around 0.25–0.3 × 10−4 J. Below this energy accumulation, modification in the surface morphology doesn’t occur. It is also found that the groove morphology is hard to obtain by even multiple laser scans if it is not well formed by single laser scan. The cracks produced during the scribing process can be characterized with several propagation morphologies. At the region of the relatively low laser energy accumulation, cracks propagating across the scan direction are only generated. However, cracks propagating both across and along the scan direction are found with the increase of the laser energy accumulation. Huge cracks (arc or sinusoidal curve shape) of several millimeters in size are produced under the very large laser energy accumulation.

Glass fracture by focusing of laser-generated nanosecond surface acoustic waves

Dynamic fracture of borosilicate glass through focusing of high-amplitude nanosecond surface acoustic waves (SAWs) at the micron scale is investigated in an all-optical experiment. SAWs are generated by a picosecond laser excitation pulse focused into a ring-shaped spot on the sample surface. Interferometric images capture the SAW as it converges towards the center, focuses, and subsequently diverges. Above a laser energy threshold, damage at the acoustic focal point is observed. Numerical calculations help us determine the time evolution of the stress distribution. We find that the glass withstands a local tensile stress of at least 6 GPa without fracture.

Effect of subplate on sheet metal weld formation in back reflection induced synergistic laser welding and its mechanism

The back reflection induced synergistic laser welding (BRIS-LW) is a newly developing weld technology which could realize X-shape welding joint with relatively low laser energy when compared with general laser welding. The aim of this study is to understand the effect and mechanism of subplate, which is the core part of BRIS-LW. Therefore, 0.8-mm-thin Ti6Al4V plates in a butt configuration were carried out with different subplate status and same laser parameters. Different subplate status includes roughness of subplate surface, subplate material, and distance between subplate and back of welding sheet. The results show that the distance between subplate and back of welding sheet is considered to be the most important factor in BRIS-LW. As the distance increased from 0.1 to 0.5 mm with a step of 0.1 mm, the appearance of welding joint changed from typical X-shape to V-shape. Experimental results indicate that the obtaining of X-shape welding joint with low laser energy threshold in BRIS-LW is due to the formation of a metal-vapor cloud auxiliary energy field at the backside of welding sheet and the auxiliary energy field is induced by the subplate. Meanwhile, the utilization of auxiliary energy field is gradually reduced with the increase of distance. Furthermore, the auxiliary energy field has a synergistic action of thermal effect, force effect, protective effect, and metal evaporation effect on the back of welding zone.

Improving the Cell Viability and Isolating Precision of Laser-induced Forward Transfer Process by Maintaining a Proper Environment with a Microchip.

Aiming to improve the laser-induced forward transfer (LIFT) cell isolation process, a polydimethylsiloxane (PDMS) layer with micro-hole arrays was employed to improve the cell separation precision, and a microchip with heater was developed to maintain the working area at 100% humidity and 37°C with the purpose to preserve the viability of the isolated cells. A series of experiments were conducted to verify the contributions of the optimization to LIFT cell isolation process as well as to study the effect of laser pulse energy, laser spot size and the titanium thickness on cell isolation. With 40µm laser spot size and 40nm thick of titanium, laser energy threshold for 100% single cell isolating succeed ratio is 7µJ. According to the staining images and proliferation ratios, the chip did help to improve the cell availability and the cells can recover from the juries at least a day earlier comparing to the samples processed without the chip. With a Lattice Boltzmann model, the cell isolation process is numerically studied and it turns out that the micro-hole makes the isolation process shift to a micro-syringe injection model leading to the lower laser energy threshold for cell separation and fewer injuries.

Terahertz photonics of microplasma and beyond

THz air photonics using laser-induced air plasma is one of the leading frontiers in the THz community. Ambient air, when excited with an intense femtosecond laser beam, exhibits the remarkable ability to generate and detect pulsed THz waves through a nonlinear optical process. Significant advances in the use of air plasma for emitting, controlling, enhancing and measuring broadband THz waves have opened up a range of research opportunities. However, one of the major challenges for the research community and in real world applications is that plasma formation requires the use of an intense laser (mJ pulse energy), but most femtosecond laser oscillators only have pulse energies in the range of pJ to tens of nJ. The investigation of THz photonics, specifically the exploration of laserinduced plasmas at the micro-nano scale and beyond, is a frontier. Microplasmas generated by tightly focused optical excitation beams with controlled polarization serve as a new THz source with its unique radiation pattern and easy operation. The laser energy threshold for THz wave generation, the power scaling and the generation efficiency from microplasmas are significantly different from those of elongated plasmas. Our estimation indicates that the micronano plasma approach could reduce the necessary optical pulse energy by five orders of magnitude, while still obtaining a comparable or better signal-to-noise ratio for THz time-domain spectroscopy. This would be made possible by the high electron density (1019 cm–3 or more) achievable with a tight focus laser excitation, which correlates with the THz generation efficiency, and the use of laser oscillators with a much higher pulse repetition rate, as compared to the currently employed amplified laser systems (100 MHz vs 1 kHz). The THz micro-nano plasma is expected to lead to key technologies that will enable further interdisciplinary research and continued advancements of numerous THz wave sensing and spectroscopy developments. It serves as a vehicle for studying the extreme THz science.

The composition of liquid atmospheric pressure matrix-assisted laser desorption/ionization matrices and its effect on ionization in mass spectrometry

New liquid atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) matrices that produce predominantly multiply charged ions have been developed and evaluated with respect to their performance for peptide and protein analysis by mass spectrometry (MS). Both the chromophore and the viscous support liquid in these matrices were optimized for highest MS signal intensity, S/N values and maximum charge state. The best performance in both protein and peptide analysis was achieved employing light diols as matrix support liquids (e.g. ethylene glycol and propylene glycol). Investigating the influence of the chromophore, it was found that 2,5-dihydroxybenzoic acid resulted in a higher analyte ion signal intensity for the analysis of small peptides; however, larger molecules (>17 kDa) were undetectable. For larger molecules, a sample preparation based on α-cyano-4-hydroxycinnammic acid as the chromophore was developed and multiply protonated analytes with charge states of more than 50 were detected. Thus, for the first time it was possible to detect with MALDI MS proteins as large as ∼80 kDa with a high number of charge states, i.e. m/z values below 2000. Systematic investigations of various matrix support liquids have revealed a linear dependency between laser threshold energy and surface tension of the liquid MALDI sample.

Analysis of Single-Event Effects in DDR3 and DDR3L SDRAMs Using Laser Testing and Monte-Carlo Simulations

This paper presents a comparative analysis of the single-event effect (SEE) sensitivity of Double Data Rate memories from different manufacturers. Two-photon laser testing is performed to extract technological information such as the memory array organization and an estimation of the cell size. SEE laser energy thresholds are compared as well as the impact of the applied power mode. Bitline upsets are experimentally observed and confirmed by an analysis based on Monte-Carlo simulations. Heavy-ion testing results, including various kinds of SEFIs, are presented and discussed.

Oligo p-Phenylenevinylene Derivatives as Electron Transfer Matrices for UV-MALDI.

Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications in the growing field of organic electronics. Yet, PVs are also versatile molecules, the optical and physicochemical properties of which can be tuned by manipulation of their structure. We report the synthesis, photophysical, and MS characterization of eight PV derivatives with potential value as electron transfer (ET) matrices for UV-MALDI. UV-vis analysis show the presence of strong characteristic absorption bands in the UV region and molar absorptivities at 355 nm similar or higher than those of traditional proton (CHCA) and ET (DCTB) MALDI matrices. Most of the PVs exhibit non-radiative quantum yields (φ) above 0.5, indicating favorable thermal decay. Ionization potential values (IP) for PVs, calculated by the Electron Propagator Theory (EPT), range from 6.88 to 7.96 eV, making these oligomers good candidates as matrices for ET ionization. LDI analysis of PVs shows only the presence of radical cations (M+.) in positive ion mode and absence of clusters, adducts, or protonated species; in addition, M+. threshold energies for PVs are lower than for DCTB. We also tested the performance of four selected PVs as ET MALDI matrices for analytes ranging from porphyrins and phthalocyanines to polyaromatic compounds. Two of the four PVs show S/N enhancement of 1961% to 304% in comparison to LDI, and laser energy thresholds from 0.17 μJ to 0.47 μJ compared to 0.58 μJ for DCTB. The use of PV matrices also results in lower LODs (low fmol range) whereas LDI LODs range from pmol to nmol. Graphical Abstract ᅟ.

Fabrication of Micro-Scale Gratings by Nanosecond Laser and Its Applications for Deformation Measurements

This paper experimentally investigated the fabrication and optimization of micro-scale gratings formed by nanosecond laser etching. The mechanism of nanosecond laser processing and the geometric phase analysis (GPA) are discussed, and the factors influencing the fabrication process including laser energy, laser fluence, and ablation threshold of material, are experimentally studied. In order to eliminate the dependence of the processing parameters on the samples, depositing Al film on a sample before laser processing is proposed for the fabrication of high-quality gratings. The energy of the laser pulse is optimized for clear line etching on Al film considering the distance between adjacent lines of parallel gratings. The optimal energy of the laser pulse is 9.8 μJ, and the optimum fluence is 9.5 J/mm2 with the waist radius of the laser beam 25.7 μm. With the optimal parameters, experimental results indicate that the highest frequency of parallel gratings is about 30 lines/mm, with a line width of 29 μm, and the distance between two adjacent laser pulses being of 10 μm. By performing tensile tests, micro-scale gratings fabricated on specimens are experimentally verified. The verification tests prove that the proposed fabrication method for the micro-scale gratings in GPA measurements is reliable and applicable, and the micro-scale gratings can be fabricated in many areas of interest, such as the crack tip, for deformation measurements. Furthermore, the adhesion between the Al film and the tested sample is strong enough so that the pattern sticks well to the sample.

Laser-Induced Breakdown Spectroscopy Applied on Liquid Films: Effects of the Sample Thickness and the Laser Energy on the Signal Intensity and Stability

Droplets of organic liquids on aluminum substrate were probed by an Nd:YAG laser, both in a steady state and during rotation at speeds 18–150 rpm. Rotation transforms the droplet into film, which estimated thickness at high speeds was below 3 μm and 20 μm for diesel and peanut oil, respectively. Line intensities from the liquid (C I) and the support (Al I) material were tracked as a function of the film thickness and the laser energy. By film thinning, the line intensities from liquid sample were enhanced up to a factor 100x; simultaneously, the LIBS signal fluctuations were reduced 5–10 times with respect to the steady droplet. In certain experimental conditions, the line intensities from the support material become very weak with respect to the C I line, indicating an efficient screening of the substrate by highly excited plasma from the liquid layer. At a fixed rotation speed, there is a laser energy threshold, dependent on the liquid thickness, above which the LIBS signal becomes stable. Here, we discuss the relative processes and optimization of the experimental conditions for the LIBS measurements frome one laser shot to another.

Secondary atomization of small hydrocarbon droplet by fourth harmonic generation of Nd:YAG pulsed laser

Atomization of small fuel droplets using a UV laser is considered experimentally under atmospheric conditions. The droplet diameters in the experiments are 30µm, 20µm, and 15µm. The maximum spatial resolution is 232nm/pixel. The temporal resolution is 100ns. The fuels under test are diesel oil (JIS K2204, No. 1), hexadecane (99.5%) and o-Xylene (98%). A Nd:YAG pulse laser operating at 266nm is used in the experiments. The maximum laser energy is 10mJ. The laser beam diameter is 5mm, and the flash time is 7ns. As a result, the diesel oil droplets of all diameters are atomized using 10mJ of laser energy. The 15-µm-diameter hexadecane droplets are not atomized. The laser energy threshold for atomization of the 30-µm-diameter o-Xylene droplets is 4.5mJ, and the calculated laser intensity is 450J/m2 under the assumption of a Gaussian distribution. The atomization delay time is almost 8µs. Moisture is observed just before atomization occurs. The moisture indicates that this phenomenon can be explained based on the heat transfer process of the laser energy.

Calculating the Threshold Energy of the Pulsed Laser Sintering of Silver and Copper Nanoparticles

In this study, in order to analyze the low-temperature sintering process of silver and copper nanoparticles, we calculate their melting temperatures and surface melting temperatures with respect to particle size. For this calculation, we introduce the concept of mean-squared displacement of the atom proposed by Shi (1994). Using a parameter defined by the vibrational component of melting entropy, we readily obtained the surface and bulk melting temperatures of copper and silver nanoparticles. We also calculated the absorption cross-section of nanoparticles for variation in the wavelength of light. By using the calculated absorption cross-section of the nanoparticles at the melting temperature, we obtained the laser threshold energy for the sintering process with respect to particle size and wavelength of laser. We found that the absorption cross-section of silver nanoparticles has a resonant peak at a wavelength of close to 350 nm, yielding the lowest threshold energy. We calculated the intensity distribution around the nanoparticles using the finite-difference time-domain method and confirmed the resonant excitation of silver nanoparticles near the wavelength of the resonant peak.

The influence of Ag nanoparticles on random laser from dye-doped nematic liquid crystals

The threshold energy and electric field response characteristic of random laser have been investigated in dye-doped nematic liquid crystal (DDNLC) with the addition of different concentrations of Ag nanoparticles (NPs). Due to the localized surface plasmon resonance (LSPR) induced by Ag NPs, random laser from DDNLC with Ag NP doping had a lower threshold energy. From another point of view, nematic liquid crystals (LCs) in a DDNLC cell with the addition of Ag NPs could be more easily influenced by the electric field, which allowed the random laser to be controlled at a lower applied voltage. The turn-off time and turn-on time of random laser also decreased in the DDNLC cells with increasing the concentration of Ag NPs. This is due to the enhancement of the electro-optical characteristic of LC and the restoring force imparted by the locally ordered LCs induced by the Ag NPs, respectively.