Chih Chih-Wei L Wei Luo ( ) Department of Electrophysics, - - PowerPoint PPT Presentation

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Chih Chih-Wei L Wei Luo ( ) Department of Electrophysics, - - PowerPoint PPT Presentation

Jul 25, 2023 259 likes •757 views

Introduction to Ultrafast Science and Technology Chih Chih-Wei L Wei Luo ( ) Department of Electrophysics, National Chiao Tung University, Taiwan Ul Ultraf rafas ast Dynami namics Lab October 06, 2020 at NTU Outline 1.

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Chih Chih-Wei L Wei Luo (羅志偉)

Department of Electrophysics, National Chiao Tung University, Taiwan

Introduction to Ultrafast Science and Technology

October 06, 2020 at NTU

Ul Ultraf rafas ast Dynami namics Lab

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SLIDE 2

Outline

  • 2. Nanoparticle fabrication
  • 1. Introduction to femtosecond laser pulses
  • 3. Nanostructure fabrication
  • 4. Ultrafast dynamics in topological insulators
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SLIDE 3

The Nobel Prize in Physics 2018

Optical Tweezers & Chirped Pulse Amplification (CPA)

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SLIDE 4

反其道而行的創新--啾頻脈衝放大

羅志偉、葉恬恬

物理雙月刊 2月號/2019 41卷第1期

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What is the ultrashort pulse?

~10-6 s ~10-9 s ~10-12 s ~10-15 s

Introduction to fs laser pulses

Vernier caliper Ruler

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SLIDE 6

The shorter pulse duration, the more papers!

1950 1960 1970 1980 1990 2000 2010 10

  • 18

10

  • 15

10

  • 12

10

  • 9

intra-cavity pulse compression XUV excitation pulse Colliding pulse mode-locking Passive mode-locking Active mode-locking

Pulse duration (sec.) Year

First laser (Ruby)

1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 500 1000 1500 2000

Femtosecond in Web of Science

  • No. of Publications

Year

Introduction to fs laser pulses

  • Prof. Ahmed Zewail

The 1999 Nobel Prize in Chemistry

  • Prof. Theodor W. Hänsch

& Prof. John L. Hall The 2005 Nobel Prize in Physics

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SLIDE 7

Ultrafast camera!!

Introduction to fs laser pulses

femtosecond laser

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SLIDE 8

What is the ultrashort pulse?

~10-6 s ~10-9 s ~10-12 s ~10-15 s

Introduction to fs laser pulses

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SLIDE 9

The possibility for nuclear fusion!

 Short pulse = intense peak power

100 mJ, 100 fs = 1 TW 1018 W/cm2 @ φ = 10 μm (1010 V/cm)

Legend Legend

Amplifier Amplifier

Mira Mira

Seed Seed

Verdi Verdi Pump Pump Evolution Evolution

Pump Pump

Short pulse, low energy Long pulse, high energy Short pulse, high energy

Legend Legend

Amplifier Amplifier

Mira Mira

Seed Seed

Verdi Verdi Pump Pump Verdi Verdi Pump Pump Evolution Evolution

Pump Pump

Evolution Evolution Evolution Evolution

Pump Pump

Short pulse, low energy Long pulse, high energy Short pulse, high energy

Introduction to fs laser pulses

  • USA National Ignition Facility

@192 laser beams Institute of Laser Engineering Osaka University

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SLIDE 10

Introduction to fs laser pulses

USA National Ignition Facility

  • Output power ~ 300 TW
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SLIDE 11
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SLIDE 12

Introduction to fs laser pulses

Free electron laser - Japan

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SLIDE 13

Researches in Ultrafast Dynamics Lab

 Selected publications  Femtosecond laser annealing  Superconductors  2D materials – Graphene, MoS2

1) Adv. Optical Mater. 1, 804-808 (2013) 2) Nano Lett. 13, 5797 (2013) 3) Nanoscale 6, 8575 (2014) 4) Nano Energy 15, 625 (2015) 5) Advanced Materials 28, 876 (2016) 6) Advanced Functional Materials 26,729 (2016) 7) Optica 3, 82 (2016) 8) npj Quantum Materials, 2, 1 (2017) 9) Optics Express 25, 33134 (2017) 10) Nano Lett. 18, 7742 (2018) 11) Phys. Rev. Materials 3, 034802 (2019) 12) Optics Express 28, 685 (2020)

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SLIDE 14
  • 4. Ultrafast dynamics in topological insulators

Outline

  • 2. Nanoparticle fabrication
  • 1. Introduction to femtosecond laser pulses
  • 3. Nanostructure fabrication
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SLIDE 15

“Can we utilize the femtosecond pulses to obtain ZnSe nanoparticles?“

Pure! Simple! Fast!

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SLIDE 16

Legend Micra10

Amplifier Oscillator

Cylindrical lens Mirror Translation stage

80 fs, 0.8 W, 80 MHz 30 fs, 2 W, 5 KHz

Iris Iris

Experimental setup

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SLIDE 17

Before laser process After laser process Dispersion in ethanol TEM image measurement

Experimental procedure

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SLIDE 18

Composition of ZnSe nanoparticles

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Normalized count Energy (keV)

Zn Se

The EDX spectrum

 The main elements in nanoparticles are zinc and selenium.  The molar ratio of Zn and Se ~ 1 : 1.

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SLIDE 19

Structural phase transition

XRD results Cubic structure

ZnSe single crystal

Femtosecond laser process

Hexagonal structure

ZnSe nanoparticles

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

Cubic (400)

Intensity (a.u.) 2θ (degree) ZnSe single crystal

Cubic (200)

20 25 30 35 40 45 50 55 60

Cubic (311) Cubic (220) Hexagonal (112) Hexagonal (103) Hexagonal (110) Hexagonal (102) Hexagonal (101) Hexagonal (002) Hexagonal (100) Cubic (111)

Intensity (a.u.) 2θ (degree)

ZnSe particles at F =290.52mJ/cm2

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SLIDE 20

The size of ZnSe particles are < 100 nm for laser fluence = 127 mJ/cm2

20nm 20nm 50nm

TEM image of ZnSe nanoparticles

  • H. I. Wang, et al., Journal of Nanomaterials 2012, 278364 (2012)
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SLIDE 21

The size of ZnSe nanoparticles

20nm 50nm

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Se nanoparticle prepared by fs Laser-induced plasma shock wave deposition

Wen-Yen Tzeng, et al., Optics Express 28, 685 (2020)

trigonal Se: t-Se monoclinic Se: m-Se amorphous-Se: a-Se

Trigonal Monoclinic / Amorphous

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SLIDE 23

Outline

  • 2. Nanoparticle fabrication
  • 1. Introduction to femtosecond laser pulses
  • 3. Nanostructure fabrication
  • 4. Ultrafast dynamics in topological insulators
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SLIDE 24
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SLIDE 25

Nanostructure on ITO films

 Pulse number-dependent nanostructure

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Nanostructure on ITO films

 Transport properties

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Nanostructure on ITO films

 X-ray photoelectron spectroscopy (XPS)

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Application I

 Effects on organic photovoltaics using fs-laser-treated ITO

Mei-Hsin Chen, et al., ACS Applied Materials & Interfaces 8, 24989 (2016)

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Application II

 Anisotropic optical properties

Chih Wang, et al., Applied Physics Letters 101, 101911 (2012)

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Application III

 The colors of ITO films before and after laser processing.

Ya-Hsin Tseng, et al., Optics Express 25, 33134-33142 (2017)

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Application IV

 The image that is displayed on the LCD can be selectively screened by varying the view angle.

Ya-Hsin Tseng, et al., Optics Express 25, 33134-33142 (2017)

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 The hexagonal ZnSe & Se nanoparticles can be fabricated by properly controlling the fluences of the irradiating fs laser.  The nanostructure with anisotropic transmission characteristics on ITO films induced by fs laser can be used for the alignment layer, polarizer and conducting layer in LCD cell.  The nanostructure on the surface of ITO films significantly attenuates blue light, which are suited to eye protection and the screening of images behind ITO films for information security.

Summary I

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Outline

  • 2. Nanoparticle fabrication
  • 1. Introduction to femtosecond laser pulses
  • 3. Nanostructure fabrication
  • 4. Ultrafast dynamics in topological insulators
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SLIDE 34

Platform for ultrafast dynamic study in Taiwan

Superconductors Heterostructures e.g., water splitting Intermetallics

 Strongly correlated electron systems

Spin-glass systems

 2D materials

Perovskite 2D transition metal dichalcogenide

 Topological insulators

Thin films Crystals

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SLIDE 35

Topological insulators (TIs)

 3D TIs: Bi2Se3, Bi2Te3, … etc.

  • H. Zhang, et al., Nat. Phys. 5, 438 (2009)
  • M. Z. Hasan, et. al., Nat .Phys. 5, 398 (2009)
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SLIDE 36

THz emission from topological insulators

Chih-Wei Luo, et al., Advanced Optical Materials 1, 804-808 (2013)

sample B.S. B.S. Delay stage ZnTe balanced diodes λ/4 lens lens WP Teflon Chopper 5.2 MHz Ti:Sapphire 50 fs @ 800 nm 1.7 W EO sampling

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SLIDE 37
  • C. M. Tu et al., Physical Review B 96, 195407 (2017)
  • J. McIver et al, Nature Nanotech. 7, 96 (2012).

Mechanism of THz emission from TIs

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SLIDE 38

Ultrashort-pulse light sources in UDL

  • Y. Normura, et al., Optics Letters 40, 423-426 (2015)

7.5 fs

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SLIDE 39

800 nm pump & ultrabroadband mid-IR probe

  • H. Shirai, et al., Phys. Rev. Appl. 3, 051002 (2015)
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SLIDE 40

800 nm pump & ultrabroadband mid-IR probe

  • H. Shirai, et al., Phys. Rev. Appl. 3, 051002 (2015)
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SLIDE 41

800 nm pump & ultrabroadband mid-IR probe

  • H. Shirai, et al., Phys. Rev. Appl. 3, 051002 (2015)
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SLIDE 42

 Sb2Te2Se single crystals (p-type)

Ultrafast dynamics in topological insulators

 Bi2Te2Se single crystals (n-type)

Wavenumber (cm-1) Delay time (ps) Wavenumber (cm-1) Delay time (ps)

∆R/R Pump beam fluence：101 (μJ/cm2) ARPES images: measured by Dr. Cheng-Maw Cheng (NSRRC)

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SLIDE 43

 Surface carrier transition

The sign changes of ∆R/R

 Free carrier absorption

Reflectivity

E: energy level, T: temperature Drude model Carrier concentration:

Reflectivity Wavenumber (cm-1) Delay time (ps) Wavenumber (cm-1) Delay time (ps)

Sb2Te2Se Bi2Te2Se

Falkovsky model

  • L. A. Falkovsky, and A. A. Varlamov, A. Eur. Phys. J. B. 56, 281(2007).
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Relaxation processes in Sb2Te2Se

Wavenumber (cm-1) Delay time (ps)

1000 1500 2000 2500 3000 3500

  • 1.6
  • 1.4
  • 1.2
  • 1.0
  • 0.8
  • 0.6
  • 0.4
  • 0.2

0.0 0.2

5 ps 4 ps 3 ps 2 ps 1 ps Shifted ∆R/R Wavenumber (cm

  • 1)

0 ps

T (K) |E| (eV) Γ (cm-1) ωp (cm-1) 2 4 6 8 2000 2500 500 1000 0.00 0.05 0.10 0.15 500 1000 1500 2 4 6 8

y ( ) Delay time (ps)

D F

Fitted by Falkovsky model

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SLIDE 45

T (K) |E| (eV) Γ (cm-1) ωp (cm-1) 2 4 6 8 2000 2500 500 1000 0.00 0.05 0.10 0.15 500 1000 1500 2 4 6 8

y ( ) Delay time (ps)

D F

Relaxation processes in Sb2Te2Se

Surface carrier transition Free carriers

  • T. T. Yeh, et al., Scientific Reports 10, 9803 (2020)
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Summary II

 Ultrabroadband mid-IR generation & detection Time-resolved + FTIR  Reveal the full ultrafast dynamics in topological insulators.

Wavenumber (cm-1) Delay time (ps)

 Apply to study the vibration dynamics of molecules in femtosecond timescale.

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Acknowledgements

TCECM

Group members

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Thank ank you u for y r your at ur attent ention!!

!!

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