Ultrafast Transient Absorption Microscopy Studies of Carrier Dynamics in Epitaxial Graphene
Introduction to FemtosecodTime-resolved Experiments at ELI … · 2018. 12. 3. · Optical...
Transcript of Introduction to FemtosecodTime-resolved Experiments at ELI … · 2018. 12. 3. · Optical...
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Introduction to Femtosecod Time-resolved Experiments at ELI Beamlines
3rd ELIps Workshop
12-14 November 2017
Dolní Břežany
Mateusz Rebarz
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� Why time-resolved spectroscopy?
� Pump-probe techniques
� Pump & Probe pulses
- supercontinuum generation
- optical parametric amplification
� Time resolution
� Dynamic range
� Optical spectroscopy stations at ELI Beamlines
Outline
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Why time-resolved spectroscopy?
Time-resolved spectroscopy: any technique that allows to measure the temporal dynamics
and the kinetics of photophysical processes
Photochemistry PhotobiologyPhotophysics
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Single photon absorption
Two photon absorption
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Free carrier absorption
ImpactIonization
Excitation Processes
Carrier-carrierscattering
Carrier-phononscattering
Radiativerecombination
Augerrecombination
Carrierdifusion
Relaxation Processes
Latticeinstability
Fast processes in semiconductors
Laserexcitation
Bondsbreaking
Latticeinstability
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How to detect ultrafast process?
Hummingbird flutters wings in 0.01 s
Exposure time 1/60 s
Exposure time 1/1000 s
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How to detect ultrafast process?
Hummingbird flutters wings in 0.01 s
Exposure time 1/60 s
Exposure time 1/1000 s
The shortest pulse of visible light in the world
380 as
Max Planck Institute of Quantum Optics in Garching, Germany
February 2016
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How to detect ultrafast process?
Hummingbird flutters wings in 0.01 s
Exposure time 1/60 s
Exposure time 1/1000 s
The shortest pulse of visible light in the world
380 as
Max Planck Institute of Quantum Optics in Garching, Germany
February 2016
The shortest pulse of visible light in ELI Beamlines
~ 5 fs
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How to detect ultrafast process?
Hummingbird flutters wings in 0.01 s
Exposure time 1/60 s
Exposure time 1/1000 s
pump-probe concept
The shortest pulse of visible light in the world
380 as
Max Planck Institute of Quantum Optics in Garching, Germany
February 2016
The shortest pulse of visible light in ELI Beamlines
~ 5 fs
Delay is equivalent to real time if duration of probe
pulse is negligible and process is perfectly reproducible
Repetition rate limit
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Electronics based methods
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Pump-probe techniques
Transient absorption
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Pump-probe techniques
Transient absorption
Transient reflection
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Pump-probe techniques
Transient absorption
Transient reflection
Stimulated Raman
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Pump-probe techniques
Transient absorption
Transient reflection
Stimulated Raman Time-resolved
X-ray diffraction
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Pump and probe pulses characteristic
Probe pulse
Pump pulse
broadband (simultaneous detection of various processes)
short (good temporal resolution)
monochromatic (good selectivity of excitation)
short (good temporal resolution)
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Pump and probe pulses characteristic
- what is the easiest (cheapest) to produce?
- what is the most sensitive to detect?
- what is the least invasive to the sample?
- what has the best penetration depth?
- what delivers shorter pulses?
Probe pulse
Pump pulse
broadband (simultaneous detection of various processes)
short (good temporal resolution)
monochromatic (good selectivity of excitation)
short (good temporal resolution)
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Pump and probe pulses characteristic
- what is the easiest (cheapest) to produce?
- what is the most sensitive to detect?
- what is the least invasive to the sample?
- what has the best penetration depth?
- what delivers shorter pulses?
Probe pulse
Pump pulse
broadband (simultaneous detection of various processes)
short (good temporal resolution)
monochromatic (good selectivity of excitation)
short (good temporal resolution) Fourier limit!
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Fourier limited pulses
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Ti:Sapphire fs laser
ELI lasers are Ti:Sapp femtosecond
lasers
E ~ 5 nJ
λ ~ 800 nm
Δλ ~ 100 nm
Δt ~ 15-35 fs
Reprate ~ 80 MHz
Oscillator: modelocking
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Ti:Sapphire fs laser
ELI lasers are Ti:Sapp femtosecond
lasers
Chirped – Pulse Amplification
E = ~ 5 mJ
λ = 800 nm
Δλ ~ 80 nm
Δt ~ 15-35 fs
Reprate ~ 1 kHz
E ~ 5 nJ
λ ~ 800 nm
Δλ ~ 100 nm
Δt ~ 15-35 fs
Reprate ~ 80 MHz
Oscillator: modelocking
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Ti:Sapphire fs laser
ELI lasers are Ti:Sapp femtosecond
lasers
Chirped – Pulse Amplification
E = ~ 5 mJ
λ = 800 nm
Δλ ~ 80 nm
Δt ~ 15-35 fs
Reprate ~ 1 kHz
E ~ 5 nJ
λ ~ 800 nm
Δλ ~ 100 nm
Δt ~ 15-35 fs
Reprate ~ 80 MHz
Oscillator: modelocking
Nobel Prize 2018
Gérard Mourou and Donna Strickland
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Generation of broadband fs pulses
Optical Kerr effect – self-phase modulation
Innn 20 +=
filamentation
Supercontinuum in condensed media
main limiting factors
multiphoton-excitation
of the material
self – focusing
of the beam
nJ uJ
• typical pulse duration ~ 100 fs• difficult to compress with prisms or gratings
due to high order dispersion
• limited energy for more advanced compression techniques(chirped mirrors, deformable mirrors, pulse shapers)
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GVD – group velocity dispersion
GVD – Group Velocity Dispersion
Refractive index is wavelength dependent
Different frequencies component of
the pulse are propagated at different
speed in dispersive material
“chirp” effect
Normal dispersion – blue slower than red
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Compression of broadband pulses
Prisms
Gratings
Deformable mirrors
Chirped mirrors
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Supercontinuum generation
Hollow Core Fiber
Neon
0.35 mJ
In noble gases the ionization
threshold is high enough that
multi-photon absorption can be
suppressed
~ 5 fs
Spectrum Time profile
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Pulse shaping
acousto-optic modulator filters the spectrumpulse shaping concept
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Pulse shaping
sound wave is tailored in the modulator
with an arbitrary waveform cardacousto-optic modulator filters the spectrum
Frequency-domain shaping Time-domain shaping
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Pump wavelength conversion
SHG - second harmonic generation
800 nm400 nm
800 nm
266 nm
SFG – sum frequency generation
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Pump wavelength conversion
SHG - second harmonic generation
800 nm400 nm
800 nm
266 nm
SFG – sum frequency generation
Parametric amplification of white light supercontinuum
Nonlinear
crystal
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Pump wavelength tuning
TOPAS (1160 – 2600 nm) NiRUVis (190 – 2600 nm)
SIG - signal
IDL - idler
SH - second harmonic
FH - fourth harmonic
SF - sum frequency
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Extension of spectral range: mid IR
Non-collinear difference frequency generation
NDFG (1160 – 12000 nm) TOPAS (1160 – 2600 nm)
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Extension of spectral range of SC
UV SC driven by 400 nm pulseVIS SC driven by 800 nm pulse
NIR SC driven by 1400 nm pulse
Neon
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Extension of spectral range to X-ray
Plasma Source
4-30 keV
100 fs
incoherent
High Harmonic
coherent
10-250 eV (5 -120 nm)
< 20 fs
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Actual time resolution
Cross correlation
∆� = ����
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Actual time resolution
Cross correlation
Beams geometry in the sample
∆� = ����
∆� = ���
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Actual time resolution
Delay line accuracy
Cross correlation
Beams geometry in the sample
∆� = ����
∆� = ���
Bi-directional repeatability
�μ� ⇨ ∆� = �. �
��μ� ⇨ ∆� = ����
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Extended time range
�� ⇨ �. ��
1 m linear stage > 10 kE
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Extended time range
�� ⇨ �. ��
1 m linear stage > 10 kE
Synchronization of amplifiers
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Detection at 1kHz
UV-VIS sensors - UV-VIS Sensors: HA S7030 (1024x64 pxl; 200-1000 nm)
- IR Sensors: InGaAs G9208-256 (256 pxl; 900-2550 nm)
- photodiodes: PDA S1227-66BQ
- PCI-board interface (16 bit A/D converter)
- controller (enabling parallel read of 2 CCD and 4 PD)
- grating and prism spectrometers
Entwicklungsbüro Stresing
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Detection at 1kHz
UV-VIS sensors - UV-VIS Sensors: HA S7030 (1024x64 pxl; 200-1000 nm)
- IR Sensors: InGaAs G9208-256 (256 pxl; 900-2550 nm)
- photodiodes: PDA S1227-66BQ
- PCI-board interface (16 bit A/D converter)
- controller (enabling parallel read of 2 CCD and 4 PD)
- grating and prism spectrometers
Entwicklungsbüro Stresing
16.7 MHz
2 MHz
Full binning
64 x 6us + 1024 x 0.5us = 896 us
How fast detector for shot-to-shot detection?
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Noise and dynamic range
16 bit AD
Dynamic range: 65536:1
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Noise and dynamic range
16 bit AD
dark (thermal) noise:
easily reduced by cooling
readout noise:
important limiting factor
balance between
readout rate and
number of binning
pixels
Dynamic range: 65536:1
Dynamic range: 6500:1
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Noise and dynamic range
16 bit AD
dark (thermal) noise:
easily reduced by cooling
readout noise:
important limiting factor
balance between
readout rate and
number of binning
pixels
long term laser stability
two choppers referencing
shot to shot laser stability
reference detectors
Dynamic range: 65536:1
Dynamic range: 6500:1
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Noise and dynamic range
16 bit AD
dark (thermal) noise:
easily reduced by cooling
readout noise:
important limiting factor
balance between
readout rate and
number of binning
pixels
long term laser stability
two choppers referencing
shot to shot laser stability
reference detectors
Dynamic range: 65536:1
Dynamic range: 6500:15 μOD
1000 shots
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Optical spectroscopy at ELI Beamlines
� Transient absorption UV-VIS-NIR (working)
� Transient absorption IR (beginning of 2019)
� 2D IR spectroscopy (2019)
� 2D UV-VIS (??)
� Stimulated Raman Spectroscopy (working)
� Transient Circular Dichroism (beginning of 2019)
� Pulse shaping + mass spectrometry (working)
� Upconversion fluorescence (2019)
� Time-Correlated Single Photon Counting (2019)
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Time-resolved ellipsometry
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Thank you for your attention