Ultrafast dynamic ellipsometry measurements of early time laser ablation of titanium thin films

Bolme, C. A.; Funk, David J.

doi:10.1007/s00339-008-4612-1

Cited by 7 publications

(5 citation statements)

References 18 publications

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“…16,17,29). On this basis we conclude that reported observations of plastic shocks with very small widths at anomalously low stresses 13 , were in reality observations of large amplitude elastic precursors (Figure 8 of Ref. 22.…”

supporting

confidence: 69%

Invariance of the Dissipative Action at Ultrahigh Strain Rates Above the Strong Shock Threshold

et al. 2011

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We have directly resolved shock structures in pure aluminum in the first few hundred picoseconds subsequent to a dynamic load at peak stresses up to 43 GPa and strain rates in excess of 10(10) s(-1). For strong shocks we obtain peak stresses, strain rates, and rise times. From these data, we directly validate the invariance of the dissipative action in the strong shock regime, and by comparing with data obtained at much lower strain rates show that this invariance is observed over at least 5 orders of magnitude in the strain rate. Over the same range, we similarly validate the fourth-power scaling of the strain rate with the peak stress (the Swegle-Grady relation).

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supporting

confidence: 69%

Invariance of the Dissipative Action at Ultrahigh Strain Rates Above the Strong Shock Threshold

et al. 2011

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“…The laser driven shock apparatus and multiple diagnostics have been detailed in various publications over several years. ,− A single pulse from a Ti:sapphire chirped pulse amplifier (CPA) was used to simultaneously generate the shock, characterize the shock interferometrically, and generate spectroscopic probe beams for electronic and vibrational absorption spectroscopy. An in-depth description of how each beam is generated and used has been reported elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…This change introduced temporally shorter chirped pulses (300 to 120 ps) but also spectrally broader pulses (12 to 35 nm fwhm). The temporal duration of the chirped laser pulse is directly related to the supported shock duration. ,− ,,, The broader spectrum of the compressed pulse primarily affected the MIR generation. There was no noticeable difference between the spectrum of the VIS radiation produced using the new CPA and the VIS radiation generated using the previous system.…”

Section: Methodsmentioning

confidence: 99%

Insight into the Chemistry of PETN Under Shock Compression Through Ultrafast Broadband Mid-Infrared Absorption Spectroscopy

et al. 2020

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Thin films of pentaerythritol tetranitrate (PETN) were shock compressed using the laser driven shock apparatus at Los Alamos National Laboratory (LANL). Two spectroscopic probes were available to this apparatus: visible white light transient absorption spectroscopy (VIS) from 400 to 700 nm and midinfrared transient absorption spectroscopy (MIR) from 1150 to 3800 cm −1 . Important PETN vibrational modes are the symmetric and antisymmetric NO 2 stretches at 1280 and 1650 cm −1 , respectively, as well as CH stretches at ∼2900 cm −1 . Shock strength was varied from approximately 3 to 55 GPa to span from the chemically unreactive regime to the regime in which fast chemical reaction took place on the 250 ps time scale of the measurements. VIS and MIR results suggest irreversible chemistry was induced in PETN at pressures above 30 GPa. At lower shock pressures, the spectroscopy showed minimal changes attributable to pressure induced effects. Under the higher-pressure reactive conditions, the frequency region at the antisymmetric NO 2 stretch mode had a significantly increased absorption while the region around the symmetric NO 2 stretch did not. No observable increased absorption occurred in the higher frequency regions where CH-, NH-, and OH-bond absorptions would be observed. A broad absorption appeared on the shoulder at the red-edge of the CO 2 vibrational band around 2200 cm −1 . In addition to the experiments, reactive molecular dynamics were carried out under equivalent shock conditions to correlate the evolution of the infrared spectrum to molecular processes. The simulations show results consistent to experiments up to 30 GPa but suggest that NO and NO 2 related features provided the strongest contributions to the shocked infrared changes. Proposed mechanisms for shocked PETN chemistry are analyzed as consistent or inconsistent with the data presented here. Our experimental data suggests C≡O or N 2 O bond formation, nitrite formation, and absence of significant hydroxyl or amine concentrations in the initial chemistry steps in PETN shocked above 30 GPa.

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“…Rebibo et al measured the normalized reflection coefficient and the phase of a laser-pumped polypropylene target by using a single-shot spectral interferometry system [13], in which the sensitivity of the refractive index of the laser-breakdown target to the electron density rise has been investigated. In 2008, Bolme et al developed an ultrafast dynamic ellipsometer (UDE) to measure the shocked refractive indices of a polycarbonate [14], which successfully decoupled the dynamic optical constant changes and the kinematic movements of the free surface. Since the UDE proposed by Bolme et al has adopted a femtosecond laser as the source, the equipment is rather expensive and picky in working conditions.…”

Section: Measurement Configuration Optimization For Dynamic Metrologymentioning

confidence: 99%

Measurement configuration optimization for dynamic metrology using Stokes polarimetry

Liu¹,

Zhang²,

Zhong³

et al. 2018

Meas. Sci. Technol.

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As dynamic loading experiments such as a shock compression test are usually characterized by short duration, unrepeatability and high costs, high temporal resolution and precise accuracy of the measurements is required. Due to high temporal resolution up to a ten-nanosecond-scale, a Stokes polarimeter with six parallel channels has been developed to capture such instantaneous changes in optical properties in this paper. Since the measurement accuracy heavily depends on the configuration of the probing beam incident angle and the polarizer azimuth angle, it is important to select an optimal combination from the numerous options. In this paper, a systematic error propagation-based measurement configuration optimization method corresponding to the Stokes polarimeter was proposed. The maximal Frobenius norm of the combinatorial matrix of the configuration error propagating matrix and the intrinsic error propagating matrix is introduced to assess the measurement accuracy. The optimal configuration for thickness measurement of a SiO2 thin film deposited on a Si substrate has been achieved by minimizing the merit function. Simulation and experimental results show a good agreement between the optimal measurement configuration achieved experimentally using the polarimeter and the theoretical prediction. In particular, the experimental result shows that the relative error in the thickness measurement can be reduced from 6% to 1% by using the optimal polarizer azimuth angle when the incident angle is 45°. Furthermore, the optimal configuration for the dynamic metrology of a nickel foil under quasi-dynamic loading is investigated using the proposed optimization method.

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Ultrafast dynamic ellipsometry measurements of early time laser ablation of titanium thin films

Cited by 7 publications

References 18 publications

Invariance of the Dissipative Action at Ultrahigh Strain Rates Above the Strong Shock Threshold

Invariance of the Dissipative Action at Ultrahigh Strain Rates Above the Strong Shock Threshold

Insight into the Chemistry of PETN Under Shock Compression Through Ultrafast Broadband Mid-Infrared Absorption Spectroscopy

Measurement configuration optimization for dynamic metrology using Stokes polarimetry

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