2. Schlossberg - Lasers and Optics

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LASERS AND OPTICS15 March 2011

Dr. Howard Schlossberg

Program Manager

AFOSR/RSE

Air Force Office of Scientific Research

AFOSR

Distribution A: Approved for public release; distribution is unlimited. 88ABW-2011-0758



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2011 AFOSR SPRING REVIEW2301A PORTFOLIO OVERVIEW

NAME: Dr. Howard Schlossberg

BRIEF DESCRIPTION OF PORTFOLIO:RESEARCH IN LASERS, OPTICS, AND THEIR APPLICATIONS

LIST SUB-AREAS IN PORTFOLIO:

- LASERS

- NON-LINEAR OPTICS- LASER-MATTER INTERACTIONS- MICRO-SYSTEMS



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• High Average Power Solid-State Lasers

• Ceramic Laser Solid-State Materials• Fiber Lasers• Thin Disk Semiconductor Lasers• Novel Concepts

• Modest Power Lasers

• Mid-Infrared Semiconductor Lasers• Mid-Infrared Fiber Lasers

• Nonlinear Optics• Nonlinear Frequency Conversion• Ultrashort Pulses

• Extreme Light• High Harmonic Generation• Mid-and Long Wave Frequency Combs• Micromachining

• Microplasmas• Plasma transistor

• Plasma chemistry• RF modulation, protection (DARPA)

Portfolio Summary



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LASERS



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• Ceramic Solid-State Laser Materials• Spatially Varying Index and Doping Concentration• Non-Isotropic hosts

• Fiber Lasers• University Based Fiber Growth Facility

• Ultra-short, Ultra-Intense Pulses• Matter Interactions, Propagation, X-Ray Beams

• Integrate with HPL JTO Programs

AFOSR Study of 6.1 Opportunities in HighEnergy and High Power Lasers

Inputs from Leading Researchers in High EnergyLaser Community

High Energy Solid-State Lasers Today are an Exercisein Mode Conversion



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SPRING REVIEW

Ceramic laser gain media offer a number of important

advantages over single crystals:• Ceramic media can be fabricated with arbitrary shapes and size, whereas single-

crystal growth techniques (e.g. the Czochralski method) set limits on the possible size.

• Ceramics are well suited to produce composite gain media, consisting e.g. of partswith different doping levels, or even different dopants. It is also possible to include a

saturable absorber section for passive Q switching.

• Spatially varying doping profiles are relatively easily possible. These aspects giveadditional freedom in laser design.

• For neodymium-doped and ytterbium-doped YAG ceramics, a significantly higherdoping concentration can be achieved without quenching effects degrading the laserefficiency.

• Some materials, e.g. yttria (Y2O3), scandia (Sc2O3) and other sesquioxides with theirhigh melting temperatures, are very difficult to grow into single crystals, and mucheasier to obtain in ceramic form, because the sintering temperature can be muchlower than the melting temperature.



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Ceramic Solid-State Laser MaterialsNon-Isotropic hosts

• Yb doped Sr5(PO4)3F (Yb:S-FAP)– Excellent properties as laser host– Prototype uniaxial material

• Precursors

• Very high magnetic fields• Re-crystallization

Precursors• Produced 10-40 nm crystals

by co-precipitation• Preliminary densification

Wu – U. Rochester



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Fiber Laser ArraysPassive Coherent Beam Combining

• What is the number of lasers that can be coherently combined in a passive cavity?

– What parameters can be adjusted to maximize this number?

• What is the optimum optical architecture for passive beam combining?

• What is the optimal design of an individual fiber laser for passive beam combining?

• What is the role of fiber nonlinearities?

• How can issues such as self -Q-switching be mitigated at exceedingly high laserpowers?

Ledger – U. MinnesotaNilsson – U. Southampton

•10 KW Single Mode Lasers

•10-20 Coherently Coupled



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•Diode-pumped gas laser

•Long interaction length allows small absorption•Enhanced efficiency possible through V-V collisions•Large mode area or coherent coupling possible

•Corwin - Kansas State U• U. New Mexico

•University of Bath

PHOTONIC BANDGAP GASLASERS



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Laser Locking

•Combines coherent and incoherent beam combining•Ultra-short pulses at high rep-rates•Scalable to high average powers

GopinathU. Colorado



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EXTREME LIGHT

DIOCLES LASER UNL• 30 J in 30 fs (1 pettawatt) every 10 seconds• 100 TW pulses at 10/sec

New Physical Regime• Electrons and heavy particles accelerated to relativistic energy in a single cycle• High quality, high energy electron beams generated• High quality x-rays, γ-rays by Compton Scattering, FEL interactions• High quality proton beams for research, medicine, homeland security

Exawatt Lasers being designed (ELI), Zettawatts contemplated• Breakdown, nonlinear optics of vacuum



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PLASMA TRANSISTOR

Eden – U. Illinois



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0 5 10 15 20 25 30 35 40 45 50 550

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Input Power (W)

Output Power (W)

Surface Distributed Bragg Reflector (S-DBR) mid-IR opticallypumped semiconductor lasers (OPSLs) pack high powerinto narrow spectral width.

1st order surfaceDBR grating

λ=2neff Λ

S-DBR OPSL

BaselineFabry-Pérotcavity OPSL

S-DBR

V10-41Uncoated80 K32 µs pulse1%

Fabry-Pérot

• 1st order surface DBR is etched on portion of opticallypumped device surface.

• When (coupling coefficient * DBR length) > 2, DBRmirror enhances longitudinal modes within band.

• Power is eff iciently transferred to modes within narrowspectral range.

• When top and front facet antireflective coatings areimplemented, > 6W qcw within 5nm FWHM is expected.

• Possible applications include spectroscopy and LIDAR

at 3-4µm were alternative sources do not exist.

3520 3540 3560 3580 3600 3620 3640

Wavelength (nm)

Intensity

~4 nm FWHM

~ 48 nm FWHM

AFOSR sponsored research at AFRL/RDLAS



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Periodically Oriented Materials

"Dr. Lynch's technology breakthrough is not only a national asset, but atestament to her dedication to science with a focus on national security,“

Dr. David Jerome, Director RY

FY11 Venture Fund Projects Approved but hold pending funding realignment

• Advanced Epitaxial Growth of Quasi-Phase- Matched Nonlinear Materials forCounter- Measures and Sensing Applications

Dr. Candace Lynch receives theHarold Brown Award, fromSecretary Michael Donley , for research funded by AFOSR



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Vibronic solid-state lasers: Cr:ZnSeand Cr:ZnS

Hi h T l



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High power Tm laser

36K. Vodopyanov, PW short course SC1012



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3-µm GaSb-based Diode Lasers

T B I f i



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Two-Beam InterferometricSpectroscopy



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Dual-comb FT spectroscopy

103K.Vodopyanov,PW shortcourseSC1012

GaSe

GaS

eOPTICAL RECTIFICATION:GaSe crystal is used for phase-matched parametricfrequency mixing of different spectral componentswithin the same pulse.

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3

800-nm10-fspulse

Mid-IRpulse

FREQUENCY

N R lt ith O i t ti



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New Results with Orientation-Patterned Gallium Arsenide



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(Not So) Extreme Light

x-ray beam• High Harmonic Generation

hncutoff = I p+3.2 I LlL2

ηα

λ

-5.5



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Phase Matching

x-ray beam

• Waveguide dispersion

• QPM

• Non-Collinear

• Counter-propagating beams



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x-ray beam

Applications of HHG

• Atomic & molecular physics, chemistry (attosecond)

• Nano-scale imaging

– Diffraction imaging (lensless)

– Attosecond resolution

• Lithography

• Medical imaging

P ti l lt f t h t ft



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Nanoscale heat transport

Electron andmoleculardynamics inpolyatomicmolecules andsurfaces

X-ray driven moleculardynamics

Lensless coherentimaging

Molecular recollisioninterferometry

– Average power ~1012 ph/sec @ 50 eV (µW)

– Perfect laser-like coherence

– Broad energy range from VUV - keV– Femto-attosec pulse duration

Practical ultrafast coherent soft x-ray source

2. Schlossberg - Lasers and Optics

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