Ns Laser Research Articles

Ultrafast nano generation of acoustic waves in water via a single carbon nanotube

Generation of ultra high frequency acoustic waves in water is key to nano resolution sensing, acoustic imaging and theranostics. In this context water immersed carbon nanotubes (CNTs) may act as an ideal optoacoustic source, due to their nanometric radial dimensions, peculiar thermal properties and broad band optical absorption. The generation mechanism of acoustic waves in water, upon excitation of both a single-wall (SW) and a multi-wall (MW) CNT with laser pulses of temporal width ranging from 5 ns down to ps, is theoretically investigated via a multiscale approach. We show that, depending on the combination of CNT size and laser pulse duration, the CNT can act as a thermophone or a mechanophone. As a thermophone, the CNT acts as a nanoheater for the surrounding water, which, upon thermal expansion, launches the pressure wave. As a mechanophone, the CNT acts as a nanopiston, its thermal expansion directly triggering the pressure wave in water. Activation of the mechanophone effect is sought to trigger few nanometers wavelength sound waves in water, matching the CNT acoustic frequencies. This is at variance with respect to the commonly addressed case of water-immersed single metallic nano-objects excited with ns laser pulses, where only the thermophone effect significantly contributes. The present findings might be of impact in fields ranging from nanoscale non-destructive testing to water dynamics at the meso to nanoscale.

Nonresonant Multiphoton Ionization of Stark Decelerated Molecules by Femtosecond Laser Pulses

Nonresonant multiphoton ionization by femtosecond laser pulses can be applied to any molecule virtually, thereby greatly enhancing the scope of Stark decelerated molecules. For comparison, we detect decelerated and trapped ammonia molecules using two different schemes: (i) nonresonant multiphoton ionization using intense femtosecond (fs) pulses in the near infrared, and (ii) resonance-enhanced multiphoton ionization using nanosecond (ns) pulses from a tunable UV laser. The observed number of ions per shot for both schemes is similar. The fs laser detection scheme suffers from an increased background, which can be effectively eliminated by subsequent mass and velocity selection. To determine the detection volume of the ns laser detection scheme, we present measurements in which the decelerated ammonia molecules are bunched to a packet with a longitudinal spread well below ∼100 μm. It is concluded that the detection volume for the ns laser detection scheme is 1.5–2 times larger than that of the fs laser detection scheme.

Particle energization in colliding subcritical collisionless shocks investigated in the laboratory

Context. Colliding collisionless shocks appear across a broad variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. Aims. The main goal of our experimental and computational work is to understand the effect of the interpenetration between two subcritical collisionless shocks on particle energization. Methods. To investigate the detailed dynamics of this phenomenon, we performed a dedicated laboratory experiment. We generated two counter-streaming subcritical collisionless magnetized shocks by irradiating two Teflon (C2F4) targets with 100 J, 1 ns laser beams on the LULI2000 laser facility. The interaction region between the plasma flows was pre-filled with a low-density background hydrogen plasma and initialized with an externally applied homogeneous magnetic field perpendicular to the shocks. We also modeled the macroscopic evolution of the system via hydrodynamic simulations and the microphysics at play during the interaction via particle-in-cell (PIC) simulations. Results. Here, we report our measurements of the plasma density and temperature during the formation of the supercritical shocks, their transition to subcritical, and their final interpenetration. We find that in the presence of two shocks, the ambient ions reach energies around 1.5 times of those obtained with single shocks. Both the presence of the downstream zone of the second shock and of the downstream zone common for the two shocks play a role in the different energization: the characteristics of the perpendicular electric fields in the two areas indeed allow for certain particles to continue being accelerated or, at least, to avoid being decelerated. Conclusions. The findings of our laboratory investigation are relevant for our understanding of the energy distribution of high-energy particles that populate the interplanetary space in our solar system and the very local interstellar medium around the heliopause, where observations have indicated evidence of subcritical collisionless shocks that may eventually go on to collide with one another.

Laser engineering of ITO/ZnO/ITO structures for photodetector applications

ZnO nanomaterials have received much attention due to their suitability for applications such as gas sensors, UV detectors, and solar collectors. However, the functionality of ZnO in optical applications is often limited by its wide bandgap (3.15 eV) which restricts the response to shorter wavelengths. In view of this limitation, there has been much interest in tuning the optical properties of ZnO through defect engineering. In this work, we show that processing ZnO thin films with nanosecond (ns) laser irradiation is a simple and effective way to introduce interband defects lowering the bandgap and increasing the sensitivity of ITO/ZnO/ITO photodetector structures at longer wavelengths. In particular, we show that the concentration of oxygen vacancies in ZnO is proportional to laser fluence below 700 mJ/cm2, but that an increase in laser fluence above this value results in thermal heating that anneals the film and lowers the relative abundance of oxygen vacancies. On the other hand, the surface morphology of ZnO does not change significantly even though the fluence reaches 700 mJ/cm2. To illustrate the way in which laser processing can be utilized to improve the optical properties of ZnO films in photodetector applications, we have fabricated transparent ITO/ZnO/ITO stacked structures and measured their response at various optical wavelengths. We find that processing with ns laser radiation is effective in enhancing the responsivity and detectivity of these devices at blue (460 nm) and UV (390 nm) wavelengths. The response of the photodetector is also increased at green wavelengths (570 nm) and red wavelengths (620 nm) when processed with laser fluences in the 480–600 mJ/cm2 range.

Propagation dynamics of the solid–liquid interface in Ge upon ns and fs laser irradiation

Monitoring the laser-induced melting and solidification dynamics of Ge upon laser irradiation is an enormous challenge due to the short penetration depth of its liquid phase. In this work, real-time pump-probe experiments in combination with finite element calculations have been employed to investigate the melting and solidification dynamics of germanium upon ns and fs laser pulse irradiation (λ = 800 nm). Excellent agreement between experiments and simulations allowed us to indirectly determine additional time- and depth-dependent information about the transformation dynamics of germanium, including the thickness evolution of the molten layer, as well as its melting and solidification velocities for the two pulse durations for different fluences. Our results reveal considerable differences in the maximum thickness of the molten Ge superficial layers at sub-ablative fluences for ns and fs pulses, respectively. Maximum melt-in velocities of 39 m s−1 were obtained for ns pulses at high fluences, compared to non-thermal melting of a thin layer within 300 fs for fs pulses already at moderate fluences. Maximum solidification velocities were found to be 16 m s−1 for ns pulses, and up to 55 m s−1 for fs pulses. Weak signs of amorphization were observed for fs excitation, suggesting that the lower limit of solidification velocities for a complete amorphization is above 55 m s−1. In addition, we show high precision measurements of the melt-in velocities over the first 20 nm by means of fs microscopy with sub-ps temporal resolution. Here, differences of the melt-in process of several orders of magnitude were observed, ranging from virtually instantaneous melting within less than 2 ps even for a moderate peak fluence up to 200 ps for fluences close to the melting threshold.

Nanosecond pulsed laser sintering of carbon nanotube – Silver nanocomposite thin films on a flexible substrate: In-situ temperature measurements and post-process characterizations

Cracks could be induced in metallic components of flexible electronics due to repeated large deformations during their service. This could affect their reliability and durability, which may be potentially enhanced by replacing the metal with a metal nanocomposite reinforced by carbon nanotubes (CNTs). Such nanocomposite thin films can be fabricated onto a flexible substrate via laser sintering of metallic nanoparticles (NPs) and CNTs, which is a fabrication method with several potential advantages. Despite previous studies by the authors on continuous-wave (CW) laser sintering, a systematic experimental study on the nanocomposite thin film fabrication by pulsed laser sintering has been seldomly reported in a paper to the best knowledge of the authors'. This current paper has reported experimental study on nanosecond (ns) laser pulse sintering of CNT-reinforced silver matrix nanocomposite thin-film lines on a substrate of polyimide. Both in-process time-resolved measurements of temperatures and post-process characterizations are performed. For the studied conditions, it has been discovered that with the same laser spot scanning speed and time-averaged power, 100 kHz laser pulses can produce much lower nanocomposite electrical resistivity than that by 25 kHz. The fundamental mechanism has been revealed through in-situ measurements of temperatures. It is expected to be related to the pulse-to-pulse heat accumulation effect generated by the laser pulses with the 100 kHz repetition rate, leading to a silver melt pool that is more continuous in time and has a longer lifetime. It has been found that with the same given average laser power, an optimum laser scanning speed exists, which leads to the minimum electrical resistivity of the sintered nanocomposite. At the corresponding optimum speeds and with the same average laser power, compared with the CW laser sintering, the ns laser pulse sintering can produce nanocomposite thin-film lines with similar (slightly smaller) electrical resistivity and much narrower widths at a much faster speed. An interesting “two-region” phenomenon has been discovered in the ns laser sintering. Its fundamental mechanism has been analyzed, which is expected to be related to surface vaporization-induced recoil pressure during laser sintering.

SiC and Ion collectors as diagnostics of laser-generated plasma at intensity of 1010W/cm2

Characterization of non-equilibrium plasma by 1010 W/cm2 IR pulsed laser irradiating metallic targets in a vacuum, has been performed employing a Faraday cup as an ion collector (IC) and a SiC interdigitated detector, connected in time-of-flight (TOF) configuration.Both detectors reveal the emitted fast UV and the slower plasma ions. The measure of energy of ions and photons has been evaluated using the TOF spectra and thin absorbers.The fast semiconductor response and its high detection efficiency give a good benchmark measurement of radiations at low energyemitted by plasma generated by ns laser pulses. Thanks to the IC detector response it is possible to evaluate the ion current emitted from the plasma. The simultaneous use of the two detectors allows to monitor and evaluate different plasma parameters, such as the time emission, the temperature, the maximum particle energy and charge state, and others.

Laser modification of Au–CuO–Au structures for improved electrical and electro-optical properties

CuO nanomaterials are one of the metal-oxides that received extensive investigations in recent years due to their versatility for applications in high-performance nano-devices. Tailoring the device performance through the engineering of properties in the CuO nanomaterials thus attracted lots of effort. In this paper, we show that nanosecond (ns) laser irradiation is effective in improving the electrical and optoelectrical properties in the copper oxide nanowires (CuO NWs). We find that ns laser irradiation can achieve joining between CuO NWs and interdigital gold electrodes. Meanwhile, the concentration and type of point defects in CuO can be controlled by ns laser irradiation as well. An increase in the concentration of defect centers, together with a reduction in the potential energy barrier at the Au/CuO interfaces due to laser irradiation increases electrical conductivity and enhances photo-conductivity. We demonstrate that the enhanced electrical and photo-conductivity achieved through ns laser irradiation can be beneficial for applications such as resistive switching and photo-detection.

Synthesis and nonlinear optical properties of 4-phenylethylene derivatives based on a large π conjugated structure

4-phenylethylene derivatives (B1, B2 and B3) with π conjugated systems were designed and synthesized by Sonogashira coupling reaction and Schiff base reaction. Under the ns laser source, the nonlinear absorption coefficients (β) of B2 and B3 are 1.85 × 10−10 m/W and 1.9 × 10−10 m/W. B2 and B3 have good light limit performance. Furthermore, the third harmonic strength of B2 and B3 is 181 and 215 times that of SiO2, respectively. The optical limiting threshold and third harmonic signal show that 4-phenylethylene derivatives will have good application potential in laser protection and frequency conversion.

Morphology evolution and corrosion performance evaluation of the amorphous Ni-P coating prepared by picosecond LECD and modified by nanosecond laser remelting

The amorphous Ni-P coating crack may further propagate with an increase in electrodeposition (ECD) time, and hence decreases the corrosion resistance. In this study, the Ni-P coating was firstly prepared by picosecond (ps) laser-assisted ECD (LECD), followed by a nanosecond (ns) laser remelting step to remove cracks. The corrosion behavior was detailed evaluated under different LECD time and processing sequence. The results show that the ns laser remelting step results in an increase in surface roughness (Sa) by about one order of magnitude, as well as phase transition from amorphous to crystalline. The LECD time length significantly affect the corrosion behavior after the remelting step, as obvious decrease in corrosion resistance compared with the non-melted surface can be observed for 40 min and 90 min LECD. In contrast, for 180 min case, the corrosion behavior has been significant improved. Longer LECD time may reduce the surface corrosion defects on the remelted coating, and hence decrease the probability of solution-defect contact and hence cracks development, thus improving corrosion resistance.

Quantitative evaluation of LAL productivity of colloidal nanomaterials: Which laser pulse width is more productive, ergonomic, and economic?

Near-IR (wavelength ≈ 1 μm) laser ablation of bulk, chemically-inert gold in water was compared for different laser pulse width in broad the range of 300 fs–100 ns, comparing a number of key ablation characteristics: mass loss, single-shot crater volume and extinction coefficient of the generated colloidal solutions taken in the spectral ranges of interband transitions and localized plasmon resonance. Comparing to related air-based ablation results, at the given fluences laser ablation in the liquid resulted in the maximum ablation yield per unit energy and maximum NP yield per pulse and per unit energy for the picosecond lasers, occurring at subcritical peak pulse powers for laser self-focusing. The self-focusing effect was demonstrated to yield in incomplete, effectively weaker focusing in the water filaments of ultrashort laser pulses with supercritical peak powers, comparing to linear (geometrical) focusing at sub-critical peak powers. At the other, nanosecond-pulse extreme the high ablation yield per pulse, but low ablation yield per unit energy and low NP yield per pulse and per unit energy were related to strong ablation plasma screening, providing mass removal according to the well-established scaling relationships for plasma. Illustrative comparison of the ablation and nanoparticle generation efficiency versus the broad fs–ns laser pulse width range was enabled in terms of productivity, economicity, and ergonomicity, using the proposed universal quantitative criteria.

Low-cost camera-based pulsed and modulated continuous wave laser detection for laser-based optical communications

A novel, low-cost, camera-based method of detecting a single nanosecond (ns) laser pulse and kHz modulated continuous wave and pulsed lasers has been developed. The detector uses a simple optical modification to a standard rolling shutter color camera combined with image processing techniques to distinguish lasers from other illumination sources and extract a laser’s wavelength and pulse repetition frequency. In addition, the detector is also capable of detecting a single ns laser pulse at any given time. Such a detector has applications in free-space optical communications (FSO comms) as a low-cost broadband method of extracting information from multiple sources and as a detector of laser range finders. A low-cost prototype (≈£600) has been developed using entirely off-the-shelf components and assessed in laboratory and field trial conditions, with the ability to measure laser wavelengths to ±5 nm and pulse repetition frequencies to within ±5 % at a distance of 660 m. In the laboratory, the prototype was also able to detect each of the 1000 pulses generated by a 10 Hz 10 ns 532-nm pulsed laser, as well as 100 pulses sent at random intervals, highlighting its capability to detect a ns pulse at any given time. This novel technology offers a low-cost method of detecting lasers and extracting their pulse repetition frequencies, with a wide field of view and high spatial resolution. Ultimately, this technology has applications in FSO comms for between vehicles or platforms of interest, with a capability of communicating with multiple targets simultaneously.

Irregular LIPSS produced on metals by single linearly polarized femtosecond laser

Currently, supra-wavelength periodic surface structures (SWPSS) are only achievable on silica dielectrics and silicon by femtosecond (fs) laser ablation, while triangular and rhombic laser induced periodic surface structures (LIPSS) are achievable by circularly polarized or linear cross-polarized femtosecond laser. This is the first work to demonstrate the possibility of generating SWPSS on Sn and triangular and rhombic LIPSS on W, Mo, Ta, and Nb using a single linearly polarized femtosecond laser. We discovered, for the first time, SWPSS patches with each possessing its own orientation, which are completely independent of the light polarization direction, thus, breaking the traditional rules. Increasing the laser power enlarges SWPSS periods from 4–6 μm to 15–25 μm. We report a maximal period of 25 μm, which is the largest period ever reported for SWPSS, ∼10 and ∼4 times the maximal periods (2.4 μm/6.5 μm) of SWPSS ever achieved by fs and ns laser ablation, respectively. The formation of triangular and rhombic LIPSS does not depend on the laser (power) or processing (scan interval and scan methodology) parameters but strongly depends on the material composition and is unachievable on other metals, such as Sn, Al, Ti, Zn, and Zr. This paper proposes and discusses possible mechanisms for molten droplet generation/spread/solidification, Marangoni convection flow for SWPSS formation, and linear-to-circular polarization transition for triangular and rhombic LIPSS formation. Reflectance and iridescence of as-prepared SWPSS and LIPSS are characterized. It was found that besides insufficient ablation on W, the iridescence density of Ta-, Mo-, Nb-LIPSS follows the sequence of melting temperatures: Ta > Mo > Nb, which indicates that the melting temperature of metals may affect the regularity of LIPSS. This work may inspire significant interest in further enriching the diversity of LIPSS and SWPSS.

Insight into the plasma oxidation process during pulsed laser deposition

AbstractThe dynamics of transient plasmas generated by ns laser ablation of Ag targets under various O2gas pressures (10−5–10 Pa) were investigated by implementing angle‐ and time‐resolved Langmuir probe (LP) analysis and space‐ and time‐resolved optical emission spectroscopy (OES). The effects of an O2atmosphere on silver oxide formation and the ionic kinetics and the overall plasma energy were systematically investigated. Measurements performed in the LP floating regime revealed the presence of three‐ionic structures with kinetic energies varying from 0.8 to 350 eV, which can be tailored by the addition of O2. The time‐modulated regime of electron temperature in the 0.5–3 eV observed for pressures higher than 2 Pa of O2could be explained by the formation and dissociation of silver oxide molecules. The energetic balance sustains molecular oxide formation, as confirmed by OES measurements, which revealed emission signatures of AgO (B 2Π3/2and X 2Π3/2) in the 350 nm (B 2Π3/2) and 460 nm (X 2Π3/2) spectral regions. Finally, thin films were deposited to understand the range of possibilities offered by pulsed laser deposition of Ag in O2. The morphology and atomic structure of the films were analysed for large‐scale deposition. Silver oxides were detected in the films starting from 2 Pa, while at higher values, we found mixtures of different AgxOyphases. A cauliflower‐like morphology was dominant above 5 Pa of O2atmosphere pressures, which signals the formation of the AgO phase in the deposited film. Our results demonstrate that the properties of deposited thin films are influenced by plasma properties.

Laser engraving of chip-breaker geometry on ceramic cutting tools

Laser texturing is a process that allows the selective removal of material by applying a high energy density over a small area during a very short time interval. Although it is generally common to use ultra-short pulse (ps or fs) lasers for tool engraving, in certain applications it is possible to use short pulse (ns) lasers. In this work, the material removal rate of an ns laser has been evaluated in chip-breaker milling on Al2O3 cutting inserts reinforced with SiC whiskers. The results obtained show that by milling chip-breaker geometries it is possible to reduce the cutting forces, however, the process parameters used are key to obtain an adequate surface finish without embrittlement of the tool. By means of an adequate design, a reduction in cutting forces of 20% was achieved; additionally, it has been proved that there is a high dependence between tool life and the milling strategy used.

Formation of metal–semiconductor nanowire heterojunctions by nanosecond laser irradiation

Laser nano-joining has emerged as a preferred technique for better device performance as it can result in stronger mechanical contacts and enhance the electrical properties between nanocomponents. It is often used to bond metallic nanostructures, but there is little information available on the applicability of the corresponding processes for creating hybrid bonds between metal and semiconductor nanomaterials. In this article, we show that Nd:YAG nanosecond (ns) laser irradiation is an effective tool for use in the nano-joining of metal–semiconductor nanowire (NW) combinations. We show that photothermal, electron–hole pair creation and plasmonic effects combine to facilitate nano-joining with Nd:YAG ns laser radiation, producing similar interfacial structures to those occurring under femtosecond laser irradiation. We find that Nd:YAG laser irradiation is effective in the production of bonds between Ag–TiO2 and Ag–CuO NW structures but that the detailed mechanism involved in the creation of these bonds depends on the bandgap energy of the semiconductor NW. Direct heating of the semiconductor through photoexcitation of excitons and electron transfer to the conduction band is significant in the Nd:YAG laser nano-joining of low bandgap materials such as CuO. Coupling of surface plasmon resonance energy to electrical carriers in the semiconductor NW at the Ag-semiconductor interface is found to be important in all hybrid systems, including those involving a wide bandgap material such as TiO2. Since the Nd:YAG ns laser is widely available, these results suggest that nano-joining of heterogeneous materials with ns laser pulses is a practical alternative to joining with ultrashort laser radiation.

Nonlinear optical fullerene and graphene-based polymeric 1D photonic crystals: perspectives for slow and fast optical bistability

Nonlinear optical (NLO) properties of materials can be enhanced by assembling them as thin polymer composite films alternating with other polymers and forming dielectric mirrors, 1D photonic crystals (1DPCs), wherein the input light intensity is increased. Based on the poly(vinyl carbazole) (PVK) and poly(vinyl alcohol) (PVA) contrasting polymer pair, variants of such structures, with graphene and fullerene in their high-index layers, have been produced. Their optical switching characteristics have been studied with ns, cw, and quasi-cw fs laser sources in the IR and with a fs laser in the visible range. We have demonstrated slow optical bistability in the polymeric 1DPCs determined by the thermal expansion of polymer composites at intensities over 100 W / c m 2 as well as fast and ultrafast optical switching due to thermo-optic and Kerr nonlinearities, respectively. Characteristic nonlinear refractive coefficients responsible for these processes were found to be n 2 t o ∼ 10 − 1 c m 2 / G W and n 2 K e r r ∼ 10 − 4 c m 2 / G W . A subpicosecond fast spectral shift of the 1DPC bandgap has been found. Our results and analysis provide a clear picture of the NLO behavior of 1DPCs at different time scales. The results stimulate the subsequent design of ultrafast switches and bistable memory cells based on polymeric 1DPCs whose micrometer thickness and flexibility offer promise for implementation into fiber and microchip configurations.

Influence of laser wavelength on the optical and structural properties of MoS2 nanoparticles prepared via laser irradiation in ethylene glycol

MoS2 nanoparticles (NPs) were prepared by nanosecond (ns) laser ablation in ethylene glycol using a Q-switched neodymium:ytterbium aluminum garnet laser at 1064 and 532 nm laser wavelengths. The influence of laser wavelengths in ns laser production of MoS2 NPs is not yet fully understood. The shape, structure, crystalline phase, stability, and optical and photoluminescence (PL) properties of NPs were studied using TEM, dynamic light scattering, scanning electron microscopy with energy-dispersive x-ray, x-ray diffraction (XRD), ultraviolet–visible (UV–Vis), PL, Fourier transform infrared, and Raman spectroscopy. The UV–Vis absorption spectroscopy showed that the optimum laser wavelength for preparing MoS2 NPs is 1064 nm. Also, the absorption peak intensity of MoS2 NPs prepared at 1064 nm was 3.95 times higher than that at a 532 nm wavelength. In the case of ablation with 1064 nm, the most of NPs had spherical shapes and well dispersed compared with 532 nm. While the samples had the same crystalline structure for both wavelengths, as the laser wavelength increased, the mean particle size decreased from 22 to 13 nm. This is because of a photofragmentation phenomenon.

Effect of time and spatial domains on monolayer 2D material interface thermal conductance measurement using ns ET-Raman

Raman-based approaches to characterizing thermal properties of nanoscale and microscale materials have proven to be powerful experimental methods. This work explores the potential of energy-transport state-resolved Raman (ET-Raman) for the precise determination of interfacial thermal conductance (G) between monolayer 2D materials and their substrates. ET-Raman employs a continuous wave laser and nanosecond (ns) pulsed laser to induce both steady state and transient heating while simultaneously collecting 2D material temperature information from the Raman signal. A 3D numerical model built using the finite volume method simulates the two differentiated thermal transport processes. The simulated temperature rises are compared with experimental Raman temperature information to extract G. In this study, we investigate the temporal effects of the pulse frequency and pulse width of the ns laser on precise characterization of G. By running multiple simulations for a range of pulsed laser frequencies and pulse widths, we determine that ET-Raman is most sensitive to precise interfacial thermal conductance measurements with short pulse widths (~below 20 ns) and with pulsing frequencies that ensure sufficient cooling time between consecutive pulses (~below 500 kHz). We also conclude that substrate thickness and laser spot size play critical roles in heat distribution and subsequent sensitivity to meaningful G measurements. As both laser spot size and SiO2 substrate thickness decrease, detection of interfacial thermal transport becomes more difficult. These results offer essential guidance in the design of future Raman-based approaches to thermal measurements using pulsed lasers.

The acceleration mechanism of shock wave induced by millisecond-nanosecond combined-pulse laser on silicon

The velocity variation law of shock wave induced by millisecond-nanosecond combined-pulse laser has been investigated experimentally. The pulse delay and laser energy are important experimental variables. The method of laser shadowgraphy is used in the experiment. Experimental results show that when the pulse delay is 2.4 ms, the ms and ns laser energy density is 301 J cm−2 and 12 J cm−2, respectively, the velocity of shock wave is 1.09 times faster than that induced by single ns pulse laser. It is inferred that the shock wave propagates in the plasma is faster than that in air. When the ms and ns laser energy density is 414.58 and 24 J cm−2, the velocity of shock wave shows rising trend with pulse delay in a range of 1.4 ms > Δt > 0.8 ms. It is indicated that with the increase of ns laser energy, the laser energy absorbed by laser-supported absorption wave increases. The mechanism of inverse bremsstrahlung absorption acts with target surface absorption simultaneously during the ns laser irradiation. Thus, the phenomenon of the double shock wave is induced. The numerical results of the phenomenon were accordance with experiment. The results of this research can provide a reference for the field of laser propulsion.