introduction to femtosecodtime-resolved experiments at eli … · 2018. 12. 3. · optical...

Introduction to Femtosecod Time-resolved Experiments at ELI Beamlines

3rd ELIps Workshop

12-14 November 2017

Dolní Břežany

Mateusz Rebarz

� 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

Why time-resolved spectroscopy?

Time-resolved spectroscopy: any technique that allows to measure the temporal dynamics

and the kinetics of photophysical processes

Photochemistry PhotobiologyPhotophysics

Single photon absorption

Two photon absorption

~

Free carrier absorption

ImpactIonization

Excitation Processes

Carrier-carrierscattering

Carrier-phononscattering

Radiativerecombination

Augerrecombination

Carrierdifusion

Relaxation Processes

Latticeinstability

Fast processes in semiconductors

Laserexcitation

Bondsbreaking

Latticeinstability

How to detect ultrafast process?

Hummingbird flutters wings in 0.01 s

Exposure time 1/60 s






The shortest pulse of visible light in the world

380 as

Max Planck Institute of Quantum Optics in Garching, Germany

February 2016






380 as


February 2016

The shortest pulse of visible light in ELI Beamlines

~ 5 fs





pump-probe concept


380 as


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

Electronics based methods

Pump-probe techniques

Transient absorption



Transient reflection




Stimulated Raman




Stimulated Raman Time-resolved

X-ray diffraction

Pump and probe pulses characteristic

Probe pulse

Pump pulse

broadband (simultaneous detection of various processes)

short (good temporal resolution)

monochromatic (good selectivity of excitation)



- 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






- 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




short (good temporal resolution) Fourier limit!

Fourier limited pulses

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



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




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


Nobel Prize 2018

Gérard Mourou and Donna Strickland

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)

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

Compression of broadband pulses

Prisms

Gratings

Deformable mirrors

Chirped mirrors

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

Pulse shaping

acousto-optic modulator filters the spectrumpulse shaping concept

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

Pump wavelength conversion

SHG - second harmonic generation

800 nm400 nm

800 nm

266 nm

SFG – sum frequency generation

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

Pump wavelength tuning

TOPAS (1160 – 2600 nm) NiRUVis (190 – 2600 nm)

SIG - signal

IDL - idler

SH - second harmonic

FH - fourth harmonic

SF - sum frequency

Extension of spectral range: mid IR

Non-collinear difference frequency generation

NDFG (1160 – 12000 nm) TOPAS (1160 – 2600 nm)

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

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

Actual time resolution

Cross correlation

∆� = ��


Cross correlation

Beams geometry in the sample

∆� = ��

∆� = ��


Delay line accuracy

Cross correlation

Beams geometry in the sample

∆� = ��

∆� = ��

Bi-directional repeatability

�μ� ⇨ ∆� = �. �

��μ� ⇨ ∆� = ��

Extended time range

�� ⇨ �. ��

1 m linear stage > 10 kE

Extended time range

�� ⇨ �. ��

1 m linear stage > 10 kE

Synchronization of amplifiers

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

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?

Noise and dynamic range

16 bit AD

Dynamic range: 65536:1


16 bit AD

dark (thermal) noise:

easily reduced by cooling

readout noise:

important limiting factor

balance between

readout rate and

number of binning

pixels




16 bit AD



readout noise:


balance between

readout rate and

number of binning

pixels

long term laser stability

two choppers referencing

shot to shot laser stability

reference detectors




16 bit AD



readout noise:


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: 6500:15 μOD

1000 shots

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)

Time-resolved ellipsometry

Thank you for your attention

introduction to femtosecodtime-resolved experiments at eli … · 2018. 12. 3. · optical...

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