Dr. Riq Parra presents an overview of his program - Ultrashort Pulse (USP) Laser Matter Interactions - at the AFOSR 2012 Spring Review.

1. Ultrashort Pulse (USP)
Laser-Matter
Interactions
08 MAR 2012
Riq Parra
Program Manager
AFOSR/RSE
Integrity  Service  Excellence Air Force Research Laboratory
15 February 2012 DISTRIBUTION A: Approved for public release; distribution is unlimited. 1

2. USP Laser Matter Interactions
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3. Characteristics of short pulse lasers
Peak
Power
Pulsewidth
Bandwidth
• The program aims to understand and control light sources exhibiting
extreme bandwidth, peak power and temporal characteristics.
• Portfolio sub-areas: optical frequency combs, high-field science,
attosecond physics.
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4. Applications of USP Lasers
Particle Acceleration Metrology
ultrahigh electric field gradients USP stabilized, ultra-wide bandwidth
• Table-top GeV electron Lasers • Ultra-stable freq sources
accelerators • Arb waveform generation
• MeV ion sources for • High precision spectroscopy
imaging • Frequency/time transfer
• Isotope production • Ultra-wideband comms
• Hadron tumor therapy • Coherent LIDAR
• Proton-based fast • Optical clocks
ignition • Calibration
Secondary Radiation Sources Propagation in media Material Science
generation of particle & photons self-channeling ultrashort, high peak power
• High power THz generation • Remote sensing • Surgery
• Extreme ultraviolet • Remote tagging • Chemical analysis (LIBS)
lithography • Directed energy • Surface property
• Biological soft x-ray • Electronic warfare modification
microscopy • Countermeasures • Non-equilibrium ablation
• Non-destructive evaluation • Advanced sonar • Micromachining
• Medical imaging/therapy • Ultrafast photochemistry
• Attochemistry
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5. Modelocked femtosecond lasers
Thorlabs
Source: Diddams, JOSA B (2010) DISTRIBUTION A: Approved for public release; distribution is unlimited. 5

6. Mode-locked lasers as broadband phase-
coherent optical sources (optical
frequency combs)
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7. Advancing Ultrafast Lasers for High-
Bandwidth 4D Metrology
Pratt & Whitney F119 PI: James Gord, AFRL/RZ
• Ultrashort pulses for propulsion measurements
• Ultrafast laser–based spectroscopic techniques for investigating the physics
and chemistry of reacting flows.
• Generate top-quality data for
• advanced concept development and model validation (R&D)
• propulsion-system performance assessment (T&E)
• weapon-system active combustion control (ACC)
• Measure everything, everywhere, all the time…
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8. Spectrally Resolved Femtosecond
CARS 1D Line Imaging
Single-shot, one-dimensional thermometry in flames PI: James Gord, AFRL/RZ
16-shot avg.
Single-shot
Key fs-CARS advantages
• >3 OOM faster data acquisition
• 1D line vs. point measurements
• Free from collisional broadening
• Nonresonant-background control
• Strong coherences
• Improved accuracy, precision
• Species-selective [n] and T
• Multiple-species excitation
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9. An optical frequency comb
fo measured via the
heterodyne between
the second harmonic
of the IR & VIS comb
components.
Repetition rate
phase-locked to a
microwave reference.
Source: Diddams, JOSA B (2010) DISTRIBUTION A: Approved for public release; distribution is unlimited. 9

10. Metrological applications
of optical frequency combs
Source: Newbury, Nature Photonics (2011) DISTRIBUTION A: Approved for public release; distribution is unlimited. 10

11. Microresonator frequency combs
CaF2 SiN rings Silica toroids
FY2012 Basic Research Initiative (BAA-AFOSR-2012-02)
Source: Kippenberg et al., Science (2011) DISTRIBUTION A: Approved for public release; distribution is unlimited. 11

12. Mode-locked lasers as high peak power
sources (high field science)
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13. Progress in peak intensity
• Over the last two decades, a 6 order of magnitude increase in achieved
focused intensities in table-top systems.
Source: CUOS website
Phenomena Relevance
Thomson scattering Gamma rays source
Laser wakefield Compact e-
acceleration accelerators
2x1022
Particle and x-ray Proton & x-ray
emission from solids sources
High harmonic Coherent EUV
generation sources
Propagation of
Filamentation
EM pulses
Laser ablation Laser machining
of solids & patterning
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14. High intensity lasers are reducing from
national lab to university scale systems
Commercial product!
Attributes LLNL Petawatt (1998) Thales Alpha 10 (2012)
Power per pulse 660 J 40 J
Pulse width 440 fs 25 fs
Focused intensity 7 x 1020 (W/cm2) n/a
Peak power 1.5 PW 1.3 PW
Size Building 14 x 19 ft2
Rep rate few shots/day 1 Hz
Gain material Nd:glass Ti:Sapphire
Thales
SIZE Alpha 10
brochure
Thales Alpha 10
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15. Laser micromachining & patterning
PI: Chunlei Guo, U of Rochester
• Ultrashort laser pulses open up novel
possibilities and mechanisms for laser-solid Colorizing metals using femtosecond lasers
interactions.
• Demonstrated femtosecond laser processing
and surface texturing techniques to engineer
surface structures & properties (e.g. darkened &
colored metals, super wicking surfaces).
• Studied nanostructure-covered laser-induced
periodic surface structures (NC-LIPSS) &
nanostructure-covered large scale waves (NC-
LSW).
NC-LIPSS NC-LSW
Super wicking surfaces: Array of parallel
microgrooves generates strong capillary force.
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16. Propagation of high-intensity USPL pulses
PI: William P Roach, AFRL/RD
• Propagation of localized high-intensity laser pulses is of
interest for remote sensing, imaging, communications and
remote interactions.
• Such propagation in air leads to self-channeling (i.e.
filaments) and plasma formation.
• AFRL/RDLA Filamentation Team is engaged in an
experimental, theoretical and computational effort to:
• Develop computational models for long-distance fs propagation
as an extended free space waveguide.
• Study filament propagation for long distances (2, 5 & 7 km test
sites available).
• Characterize fs-laser filament physics necessary for
coupling/confining external EM-Fields.
• Understand filamentation induced electrical shorting.
High-performance
GPU computing
enclave 9-inch filament bundle propagation
through kV-level E-Field
Range
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17. Optical breakdown of air triggered by
femtosecond laser filaments
PI: Pavel Polynkin, Arizona
• Generation and 200x enhancement of dense
plasma channels at range via dual-pulse
femtosecond-nanosecond laser excitation.
• Control of femtosecond laser filamentation
through laser beam engineering. Extended bottle-
like plasma-channel distributions using vortex
beams and high order Bessel beams.
100 laser shots
fs pulse only
Single shot
fs + ns pulses
Bottle-like filament
patterns produced by
vortex beams in water
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18. High Harmonic Generation (HHG)
Microscopic single-
atom physics of HHG
Macroscopic phase-matched
harmonic emission WATER WINDOW
2mm
0.8mm
lLASER=3.9 mm
B C N O Fe Co Ni Cu
Source: Popmintchev et al., Nat Photonics (2010),
Popmintchev et al., CLEO postdeadline (2011) DISTRIBUTION A: Approved for public release; distribution is unlimited. 18

19. Direct Frequency Comb Spectroscopy
in the Extreme Ultraviolet
PI: Jun Ye, U of Colorado
• Generating frequency combs in the extreme
ultraviolet (XUV) via high harmonic generation
(HHG) in a femtosecond enhancement cavity.
• Demonstrated generation of >200 µW per
harmonic down to 50 nm.
• Ultrahigh precision spectroscopy below the
100 nm spectral region:
• Direct frequency comb spectroscopy of Argon
transition at 82 nm with resolved 10 MHz
linewidth (atomic thermal motion limited). 47 nm 71 nm 82 nm 97 nm 119 nm
10 MHz Ar @ 82 nm
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20. Diocles 100 TW laser system
PI: Donald Umstadter, U of Nebraska
• Nd:YAG pumped Ti:Sapphire
• 3.5 J in < 30 fs, 100 TW @ 10 Hz
Focal spot
Spot size (FWHM) = 16 microns
Enclosed energy > 75-80 %
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21. Laser-driven x-rays generation
(0.1 – 10 MeV)
PI: Donald Umstadter, U of Nebraska
• Scattering from a 300 MeV electron beam
can Doppler shift a 1-eV energy laser
photon to 1.5 MeV energy.
• Demonstrated > 710 MeV electron beams
with no detectable low-energy
background.
Scattering
Laser Pulse
Experimental geometry Energy tunability from 0.1 – 0.8 GeV.
for generating x-rays via Monoenergetic: ΔE/E ~ 10 %
Low angular divergence: 1-5 mrad
Thomson scattering
E-Beam
> 710 MeV
electrons
Super
Sonic
Nozzle
• Proof-of-principle experiments are
underway.
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22. Repetitive petawatt-class laser
PI: Donald Umstadter, U of Nebraska
• Completed upgrade to 0.7 PW
@ 0.1 Hz.
10-cm Ti:Sapphire power amplifier PW Specifications
Wavelength 805 nm
25-J Nd:glass pump lasers Pulse duration < 30 fs
Rep rate 0.1 Hz
Pulse energy 20 J
Peak power 0.7 PW
Strehl ratio 0.95
Max intensity (f/2) 1x1023 W cm-2
New gratings for pulse compressor
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23. Mode-locked lasers as sources of
ultrashort EM pulses (attosecond physics)
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24. Generation of single attosecond
photon pulses
Streaking spectrogram Retrieved intensity profile
www.attoworld.de
Source: Corkum, Nature Physics (2007),
Goulielmakis, Science (2008) DISTRIBUTION A: Approved for public release; distribution is unlimited. 24

25. Attosecond pulses provide a new set
of metrology tools
Source: Krausz, RMP (2009) DISTRIBUTION A: Approved for public release; distribution is unlimited. 25

26. Sub-cycle optical pulses for isolated
attosecond pulse generation
PI: Franz Kaertner, MIT
• Coherent wavelength multiplexing of high High-energy optical
energy pulses, spanning two octaves, into waveform synthesizer
a non-sinusoidal waveform with sub-cycle
features.
• Shortest high-field transient lasts
0.8 cycles of the carrier frequency.
• Unique, scalable approach to higher
energies and rep rates for high average
power sources of isolated attosecond
pulses.
Synthesized waveform Computed isolated attosecond pulse
0.8 cycles
Waveform supports
directly isolated soft
X-ray pulse with
150 as duration (with
no gating).
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27. Summary and outlook
The program aims to understand
and control light sources exhibiting
extreme temporal, bandwidth and
peak power characteristics.
Optical frequency combs High-field laser physics Attosecond science
ultra-wide bandwidths high peak powers ultrashort pulsewidths
• Spectral coverage to exceed an • Laser-solid interactions. • Efficient, high-flux generation.
octave with high power/comb. • Fs propagation in media. • Pump-probe methods.
• Coherence across EUV-LWIR. • Sources of secondary photons. • Probe atoms/molecules &
• Novel resonator designs (e.g. • Compact particle accelerators. condensed matter systems.
micro-resonator based). • High peak power laser • Attosecond pulse propagation.
• Ultra-broadband pulse shaping. architectures. • Novel attosecond experiments.
• … • High repetition rates. • Fundamental interpretations of
• New wavelengths of operation. attosecond measurements.
• … • …
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