2045

Imaging of laser-induced microexplosions in dielectrics using
time-resolved X-ray diffraction technique[1] Organization
Leader：Dr. Arturas Vailionis(Stanford Nano Shared Facilities, Geballe
Laboratory for Advanced Materials)
Representative：Prof. Vygantas Mizeikis(Research Institute of Electronics, Shizuoka
University, Japan)
Participants：
Prof. Akira Saito(Division of Precision Sci. & Technology andApplied Physics, Graduate School ofEngineering, OSAKA University, Japan)
Prof. Atsushi Ono(Research Institute of Electronics, Shizuoka
University, Japan)
Prof. Saulius Juodkazis (Centre of Microphotonics,
Swinburne University of Technology, Melbourne,Australia)[2] Research progress
The purpose of this project is to use time-resolved
monitoringofformation
ofhigh-pressurehigh-temperature (HPHT) phases of materials during their
excitation by powerful ultrashort laser pulses. The
principle of HPHT laser modification and main results
achieved in sapphire (Al2O3) are described in an earlier
publication co-authored by some of the participants of thisproject (Vailionis, A., et al., “Evidence of superdense
aluminium synthesized by ultrafast microexplosion”,
Nature Communications 2, 445 (2011)). In sapphire,nanocrystals of super-dense aluminum phase weresynthesized via extreme pressure and temperature
conditions during laser-induced microexplosions. The newbcc-Al phase was identified from steady-state X-ray
diffraction (XRD) characterization of laser-processedregions in sapphire. It was suggested that aluminum
formation is due to spatial separation between oxygen andaluminum ions in a highly-excited plasma, which occurs

Fig. 1. The principle of LIMT (a), formation of a voidsurrounded by a shell of densified material, anddetection of new phase using XRD (b), model ofbcc-Al formation in compressed sapphire in temporaland spatial domains (c).
within the time scale of a few tens of picoseconds after
excitation by a femtosecond laser pulse. Schematic
explanation of bcc-Al laser formation during
microexplosions is given in Fig. 1.
This research project is aimed at adding time resolution to
the above XRD experiments, i.e., the ability to monitor
transient XRD patterns ny X-ray pulse passing thelaser-affected region with a desired time delay after thelaser pulse that initiated the microexplosion. By repeating
microexplosion – pulsed XRD observation cycle atvarious delay times, temporal development of bcc-Al
phase in sapphire can be visualized. More specifically,goals pursued by this project are:1) Development of novel characterization technique fortime-dependent studies of Warm Dense Matter using
ultrafast laser-pump x-ray-probe;2) Understanding the creation and evolution of novel
phases of matter under extreme conditions;3) Development of knowledge and understanding of theeffects of extreme conditions on materials
performance and stability;
4) Practical use of laser-induced micro-explosion tocreate HPHT phases in materials other than sapphire.

[3] Results1) Opto-mechanical setup for time-resolved XRD
experiments was developed. Its conceptual features areshow schematically in Fig. 2(a). The main feature of thissetup is capability to overlap spatially a femtosecond laser
pulse and an X-ray pulse in the sample under investigation,with temporal delay between the two pulses controlled by
an optical delay line within the range from zero to a few
nanoseconds. Each laser pulse exposes a new pristine
region in the sample under investigation, while delay of
X-ray pulse is varied systematically from negative (X-raybefore the laser pulse) to positive (X-ray after the laserpulse). XRD pattern is recorded versus the delay, and it isexpected that temporal development of X-ray diffraction
pattern can be observed. From this development,
formation of bcc-Al or other phases of matter underHPHT conditions can be visualized experimentally. The
proposed experiments depend on the availability of
temporally-synchronized fs laser and X-ray pulses, which
is only available in a few facilities worldwide, one of them
being Stanford University SLAC Linac Coherent LightSource. It is available on a competitive basis, i.e.,scientifically sound application for X-ray beamline must tobe submitted, and approved for implementation by SLAC
management body. Therefore, significant part of efforts
during this year was directed towards the development ofbeamline application. If approved, Stanford University
SLAC Linac Coherent Light Source facility will provide
synchronized X-ray and optical pulses, whereas precise
implementation of the interaction between the X-ray andoptical pulse must be customized by the end user. Hence,
it is necessary to prepare opto-mechanical setup thatenables focusing of the fs laser beam into the sample
investigated. The setup must be portable, i.e., can be
carried to the X-ray facility. For this purpose, a compact

Fig. 2. Fig. 2 Dynamic monitoring of modification due
to laser-induced microexplosions using time-resolved
XRD technique, schematic principle (a), prototype ofportable optical microscope system for practical dynamic
XRD monitoring experiments.

optical microscope, which enables focusing of the opticalpulses into the sample and in situ observation of themicroexplosions, was prepared. This setup is shown in Fig.
2(b), with expected propagation of X-ray and opticalbeams indicated by the arrows. In the present setup,translation of the sample is achieved using simple
manually-controlled mechanical translation stage, which isinconvenient for use. In the future studies the setup will beequipped with a transducer-controlled stage to facilitate
automatic translation of the sample with each laser shot tofacilitate exposure of pristine regions of the sample witheach laser pulse.
2) 3D tomography XRD experiments on certain biologicalsamples were performed aiming to visualize their internalstructure. Nanoscale optical and structural properties ofsilk have been measured from 100-nm-thick longitudinalslices of silk fibers with ∼ 10 nm resolution. X-ray
tomography and diffraction was used for structuralcharacterization.
Sub-wavelength
resolutionindemonstrated true nanoscale characterization of silk
sample with nano-scale resolution in 3D. These results are
currently under preparation for publication in ahigh-impact scientific journal.

(3-2) Ripple effects and further developments

Fig. 3. X-ray tomography 3D rendered volume of abunch of white silk Bombyx mori fibers at 3.15 μm pixel
resolution. The bunch was made of degummed single
strand silk fibers.
hyperspectral mapping of absorbance and molecularorientation were carried out for comparison at IR
wavelengths using synchrotron radiation. Reliable
distinction of transmission by only 1-2% due to anisotropyof amide bands was obtained. Nanoscale composition ofsilk defining its unique properties via a hierarchial
structural anisotropy can be analysed at the highest spatial
resolution corresponding to the size of β-sheets, thecrystalline building blocks of silk. Typical 3D image of aa bunch of white silk Bombyx mori fibers is shown in Fig.
3. In addition, spectral characterization, lateral mapping
and transmission with deep sub-wavelength resolution at
IR molecular fingerprinting spectral window using thin
100 nm lateral slices of silk was performed. Absorbanceand reflectance spectra of silk with resolution of SNOM
tip (i.e. on the order of ∼ 10 nm) were obtained.
Absorbance from nano-thin silk slices with only 1.5% of
the wavelength measured with a beam with lateral spot
diameter compa rable with the IR-wavelength werereliably measured and mapping across the silk fiber slice
was obtained with a high fidelity. Orientational map at theabsorbance bands was obtained. These studies have

Exchange of scientific expertise between the participants
was very helpful for coordination of experimental andtheoretical work towards the goal of this project. Also, it
has contributed to strengthening of domestic andinternational collaboration at Research Institute ofElectronics. Exchange of scientific expertise between theparticipants was very helpful for coordination ofexperimental and theoretical work towards the goal of thisproject. Also, it has contributed to strengthening ofdomestic and international collaboration at ResearchInstitute of Electronics. Joint work and discussions
between the participants of this project have broadened thescope of existing domestic and international researchcollaborations at RIE, as well as opened new venues forcollaboration in the future.
[4] Achievements
List of publications:

(1)

(2)

I. Faniayeu, S.Khakhomov, I.Semchenko, V.
Mizeikis, Highly transparent twist polarizermetasurface, Appl. Phys. Lett. 111, 111108(2017).
Faniayeu, V. Mizeikis, Vertical split-ringresonator perfect absorber metamaterial for IR
frequencies realized via femtosecond direct laser
writing, Appl. Phys. Expr. 10 (2017).

(3) V. Mizeikis, Direct laser writing of electromagnetic
metasurfaces for infra-red frequency range (Invitedtalk), SPIE Photonics West 2018, San Francisco
CA, Jan. 27-Feb. 1 (2018)(4) V. Mizeikis, Z. Hayran, H. Kurt, D. Gailevicius, M.
Malinauskas,S.

Juodkazias,

K.

Staliunas,

Fabrication of optical field concentrators based on
3D chirped photonic crystals by direct laser writing
technique, Meta 2017, Incheon, Korea, July 25-28(2017).

Travelling report
Name:
Affiliation:
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Destination:
Purpose:Name of receiver:Name:
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Dr. Arturas Vailionis
Stanford Nano Shared Facilities, Geballe Laboratory for Advanced Materials
2017.11.27-12.03
Shizuoka University, JapanTo carry out a joint research, plan the future collaboration, participate at the mini-workshop andreport previously obtained results.
Prof. Vygantas Mizeikis
Assoc. Prof. Akira Saito
Division of Precision Sci. & Technology and Applied Physics, Graduate School of Engineering,Osaka University, Japan2017.11.28-29
Shizuoka University, JapanTo carry out a joint research, plan the future collaboration, participate at the mini-workshop andreport previously obtained results.
Prof. Vygantas Mizeikis