non-linear optics
DESCRIPTION
Note of non-linear optics lectureTRANSCRIPT
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Laboratoire Temps – Fréquence (LTF)
Thomas Südmeyer Time/Frequency Laboratory, Physics Institute, University of Neuchatel Les Houches, 23.04.2015
Ultrafast OPOs and OPGs. Novel high power sources and their challenges
Laboratoire Temps – Fréquence (LTF) 23.04.2015
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Laboratoire Temps – Fréquence (LTF)
The Time/Frequency Laboratory at the University of Neuchâtel
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Laboratoire Temps – Fréquence (LTF)
The Time/Frequency Laboratory at the University of Neuchâtel
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Laboratoire Temps – Fréquence (LTF)
The Time/Frequency Laboratory at the University of Neuchâtel
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Laboratoire Temps – Fréquence (LTF)
2015 Les Houches NLO School
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Laboratoire Temps – Fréquence (LTF)
2015 Les Houches NLO School
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Laboratoire Temps – Fréquence (LTF)
2015 Les Houches NLO School
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
What is ULTRAFAST?
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Laboratoire Temps – Fréquence (LTF)
Resolving fast events
Cinema: time between images 124 Hz
= 42 ms
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Laboratoire Temps – Fréquence (LTF)
The horse in motion
Baronet, 1794
www.wikipedia.org
George Stubbs (1724-1806): English painter, best known for his paintings of horses.
Whistlejacket, 1762
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Laboratoire Temps – Fréquence (LTF)
Fast mechanical shutter photography E. Muybridge in 1878: understand horse gallop using fast photography in the ms-domain
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Laboratoire Temps – Fréquence (LTF)
Fast flash photography Harold E. Edgerton (1903-1990): understand fast processes using flash light (limited by duration of flashes to µs-domain)
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Laboratoire Temps – Fréquence (LTF)
Fast flash photography Harold E. Edgerton (1903-1990): understand fast processes using flash light (limited by duration of flashes to µs-domain)
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Laboratoire Temps – Fréquence (LTF)
Fast flash photography Harold E. Edgerton (1903-1990): understand fast processes using flash light (limited by duration of flashes to µs-domain)
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Laboratoire Temps – Fréquence (LTF)
Fast flash photography Harold E. Edgerton (1903-1990): understand fast processes using flash light (limited by duration of flashes to µs-domain)
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Laboratoire Temps – Fréquence (LTF)
Femtochemistry by A. H. Zewail in 1994 A. H. Zewail in 1994: understand transition states in chemical reactions using fs-pulses
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Laboratoire Temps – Fréquence (LTF)
Scales
picosecond 10–12 s
femtosecond 10–15 s
nanosecond 10–9 s
Time
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Laboratoire Temps – Fréquence (LTF)
Ultrafast laser pulses
Observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
Access ultrashort time scales
interconnects optical clocking
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Laboratoire Temps – Fréquence (LTF)
Ultrafast laser pulses
Observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
Access ultrashort time scales
Concentrate in time and space Achieve extremely high intensities • material processing, eye surgery, … • biomedical imaging, …. • high field science, …
40x
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Laboratoire Temps – Fréquence (LTF)
Ultrafast laser pulses
Observe and use fast dynamics • understand chemical reaction dynamics • fast communication • …
Access ultrashort time scales
Concentrate in time and space
Broad optical spectrum
Achieve extremely high intensities • material processing, eye surgery, … • biomedical imaging, …. • high field science, …
Generate ultrastable frequency combs • high precision spectroscopy • optical clocks • …
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Laboratoire Temps – Fréquence (LTF)
Key advantage of laser light: coherence
Spatial coherence Propagation over long distances & reduced divergence…
… or extremely small spot & high divergence
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Laboratoire Temps – Fréquence (LTF)
Key advantage of laser light: coherence
Long duration and very small spectrum …
… or short pulses and wide spectrum
⇒ Ultrafast lasers and frequency combs!
Spatial coherence Temporal coherence Propagation over long distances & reduced divergence…
… or extremely small spot & high divergence
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Laboratoire Temps – Fréquence (LTF)
Continuous-wave laser
Light circulates in resonator
Losses compensated by gain in laser medium (which is externally pumped)
Gain saturates to a level that it compensates the losses
Light emission typically continuous
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Laboratoire Temps – Fréquence (LTF)
Passively modelocked laser
Short pulse circulates in cavity (fs-ps)
High repetition rate pulse train at the output (MHz-GHz)
Pulse formation process initiated and stabilized by saturable absorber in the laser cavity
Steady-state pulse parameters: governed by interplay of gain, (saturable) loss, dispersion, Kerr nonlinearity, etc.
Saturable loss
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Laboratoire Temps – Fréquence (LTF)
Modelocking and frequency combs
http://www.physik.uni-wuerzburg.de/femto-welt/pulsframe.html
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Laboratoire Temps – Fréquence (LTF)
A 5 fs pulse
λ/c = 2.7 fs @800 nm
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Laboratoire Temps – Fréquence (LTF)
A 5 fs pulse
speed of light
5 fs ⋅ 𝑐𝑐 = 1.5 µ𝑚𝑚
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Laboratoire Temps – Fréquence (LTF)
SESAM (Semiconductor Saturable Absorber Mirror)
Animation: http://www.rp-photonics.com/mode_locking.html
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Laboratoire Temps – Fréquence (LTF)
SESAM (Semiconductor Saturable Absorber Mirror)
DBR mirror semiconductor saturable absorber
• Semiconductor absorber
• Integration in mirror structure
U. Keller, et al., IEEE J. Sel. Top. Quant. 2, 435 (1996)
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Laboratoire Temps – Fréquence (LTF)
SESAM (Semiconductor Saturable Absorber Mirror)
• Key parameters – saturation fluence Fsat – modulation depth ∆R – nonsaturable losses ∆Rns
– roll-over F2 – recovery time τ
DBR mirror semiconductor saturable absorber
• Semiconductor absorber – typically QW or QD layer(s) – number of layers – growth temperature – material composition, …
• Integration in mirror structure – field strength in absorber – dispersion – reflectivity, OC, …
U. Keller, et al., IEEE J. Sel. Top. Quant. 2, 435 (1996)
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Laboratoire Temps – Fréquence (LTF)
Key parameters: pulse energy
repetition rate average power ( = Ep frep) pulse duration
peak power ( ∝EP / τP )
Ep
frep Pave
τp Ppeak
… generate coherent light pulses with pico- or femtosecond duration
frep : pulse repetition rate frequency
fCEO : carrier envelope offset frequency
fn = fCEO + nfrep
Frequency comb: frequency domain
time domain TR = 1 / frep
τp
Ultrafast laser pulses
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
Industry: High-precision, high-speed micromachining Required • High EP > 10 µJ • High Ppk > 10 MW Wanted • High frep (MHz) Liu, et al., Proc. SPIE,
Vol. 5713, 2005
T. Südmeyer, et al., Nat. Phot. 2, 599 (2008)
Fuel injection nozzles Stents Inkjet nozzles
Nolte, et al., Adv. Eng. Mater. 2, 2000
Profeta et al., Industrial Laser Solutions, 2004
Science: Strong-field physics applications
HHG Spectroscopy T. Auguste, et al.,
PRA 80, 033817 (2009)
Required • High Ipeak > 1014 W/cm2
• Short pulses p < 100 fs Wanted • High frep (MHz)
High average power Pav = Epˑ frep
Attosecond science
A. Pfeiffer et al., Nat. Phys. 8, 76 (2012)
High average power Pav = Epˑ frep
Applications for high power sources
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Laboratoire Temps – Fréquence (LTF)
Frontier: average power and pulse energy
High energy and MHz
T. Südmeyer, et al., “Femtosecond laser oscillators for high-field science”, Nature Photonics 2, 559 (2008)
Industrial applications • increase throughput, • reduce costs per item, …
Scientific applications
• reduce measurement time, • increase signal-to-noise, • MHz XUV sources, …
Nolte, et al., Adv. Eng. Mater. 2, 2000
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Laboratoire Temps – Fréquence (LTF)
• Operation at reduced peak intensity
• Reduced interaction volume
Chirped pulse amplification (CPA) : 830 W, 640 fs Innoslab : 1.1 kW, 615 fs P. Russbueldt, et al., Opt. Letters 35, 4169-4171 (2010) T. Eidam, et al., Optics Letters 35, 94-96 (2010)
Fiber Slab Thin disk
Key for high average power: heat removal
• Optimization of surface-to-volume ratio for efficient cooling
Key for ultrafast: reduce nonlinearities
High average power ultrafast sources
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Laboratoire Temps – Fréquence (LTF)
• Operation at reduced peak intensity
• Reduced interaction volume
Chirped pulse amplification (CPA) : 830 W, 640 fs Innoslab : 1.1 kW, 615 fs P. Russbueldt, et al., Opt. Letters 35, 4169-4171 (2010) T. Eidam, et al., Optics Letters 35, 94-96 (2010)
Fiber Slab Thin disk
Key for high average power: heat removal
• Optimization of surface-to-volume ratio for efficient cooling
Key for ultrafast: reduce nonlinearities
High average power ultrafast sources
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Laboratoire Temps – Fréquence (LTF)
Highest average powers and highest energies of any ultrafast oscillator technology
Ep = 80 μJ
τp = 1.07 ps frep = 3 MHz Pav = 242 W
Ep = 17 µJ Pav = 275 W τp = 583 fs frep = 16.3 MHz
C.J. Saraceno, et al., Optics Express 20, 23535 (2012)
SESAM Modelocked Thin Disk Lasers
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Laboratoire Temps – Fréquence (LTF)
Challenges for high power operation
• Pulse formation – sustain high intracavity intensities – avoid mode locking instabilities
saturable reduced losses for absorber pulsed operation
cw mode locking
EP = Pavg ∙ TR
QML
Challenges • TEM00 operation at high average power
– efficient heat removal – suitable cavity design – suitable broadband gain material
QML cw mode locking QML
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Laboratoire Temps – Fréquence (LTF)
Challenge: Fundamental mode operation despite high thermal load - Suitable gain material (good optical quality, high thermal conductivity)
- Suitable gain geometry (efficient heat removal)
Thin disk laser A. Giesen, et al., Appl. Phys. B 58, 365 (1994)
- Efficient heat removal through back side
- Power scalable by increase of mode diameter D (constant intensities)
- 1D longitudinal heat flow → reduced thermal lensing
Thin disk laser
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Laboratoire Temps – Fréquence (LTF)
Multi-pass pumping scheme for efficient absorption
Pump module - Typical single-pass absorption 8% - 15% - Pump module with up to 32 passes available (here 24 passes) - Typical over 98% of absorbed pump light - Homogeneous pump light distribution - Low demand on pump brightness (pump diameters of mm-cm)
pump fiber disk
parabolic mirror
Front view
Thin disk laser
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Laboratoire Temps – Fréquence (LTF)
Modelocked thin disk laser
Animation by Martin Hoffmann
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Laboratoire Temps – Fréquence (LTF)
• efficient heat removal: → material properties: thermo-mechanical
and spectroscopic properties → disk quality: thickness, diameter → contacting
• suitable cavity design
Challenge 1: TEM00 operation at high average power
Yb:YAG: the standard thin disk material • large disks on diamond with excellent quality
commercially available • 500 W fundamental transverse mode
(M2<1.1) demonstrated#1
• 1.1 kW nearly fundamental mode (M2<1.5) #2
#1 A.Killi, et al., Proceedings of the SPIE, Volume 7193, 2009 #2 Peng, et. al., Opt. Lett 38, 10, pp. 1709-1711, 2013
< 100 µm thick
glued on water cooled diamond
High-power modelocking: challenges
C. R. E. Baer, et al., Optics Express 20, 7054-7065 (2012)
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Laboratoire Temps – Fréquence (LTF)
• efficient heat removal: → material properties: thermo-mechanical
and spectroscopic properties → disk quality: thickness, diameter → contacting
• suitable cavity design C. R. E. Baer, et al., Optics Express 20, 7054-7065 (2012)
Challenge 1: TEM00 operation at high average power
High-power modelocking: challenges
Many other promising materials currently being investigated!
• Yb: CALGO • >70% slope efficiency • 62 fs pulses
• Yb doped sesquioxides • Etc…
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Laboratoire Temps – Fréquence (LTF)
Challenge 2: Pulse formation at high intracavity peak power
➝ Soliton modelocking: balance self-phase modulation and negative dispersion ➝ Thin-disk geometry: excellent for low nonlinearities ➝ Avoid modelocking instabilities from excessive nonlinearities at very high intracavity
levels ➝ Origin of nonlinearities: mostly air in resonator
F. X. Kartner and U. Keller, Opt. Lett. 20(1), 16–18 (1995) R. Paschotta and U. Keller, Appl. Phys. B 73(7), 653–662 (2001)
Avoid excessive nonlinearities!
High-power modelocking: challenges
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Laboratoire Temps – Fréquence (LTF)
Helium flooding 45 W, 11 µJ, 790 fs
Harnessing intracavity nonlinearities
n2,air ≈ 3.10-23 m2/W n2,He ≈ 8.10-26 m2/W (≈ 400 times lower)
S. Marchese, et al., Optics Express 16, 6397-6409 (2008)
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Laboratoire Temps – Fréquence (LTF)
Helium flooding 45 W, 11 µJ, 790 fs Multiple passes 145 W, 41 µJ, 1.1 ps
Harnessing intracavity nonlinearities
number of passes gain per roundtrip
efficient laser operation at lower OC rate for a given output power: reduced nonlinearities
D. Bauer, et al., Optics Express 20, 9698-9704 (2012)
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Laboratoire Temps – Fréquence (LTF)
minimum nonlinearity: higher intracavity peak power can be tolerated
easy adjustment of SPM by adjusting pressure minimum pointing instabilities, cleanliness
Helium flooding 45 W, 11 µJ, 790 fs Multiple passes 145 W, 41 µJ, 1.1 ps Vacuum 275 W, 17 µJ, 580 fs Vacuum 240 W, 80 µJ, 1.07 ps
C.J. Saraceno, et al., Optics Express 20, 23535 (2012)
Harnessing intracavity nonlinearities
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Laboratoire Temps – Fréquence (LTF)
First design (275 W modelocked laser): • 17 MHz cavity with one double-pass through the disk • OC rate used for modelocking experiments: 11% • Problems with thermal effects in dispersive mirrors
EP = Pavg ∙ TR Increase cavity length to increase pulse energy!
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
New cavity: Two double-passes through the disk: higher gain, efficient operation with higher Toc reduced intracavity power for lower thermal effects
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
New cavity: Two double-passes through the disk Beam shaping Thin-film polarizer for polarization selection
frep = 5.8 MHz Toc = 25 %
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
D = n ∙ d = 23.4 m
MPC-length
Cavity extension with Heriott-type Multi-Pass Cavity (MPC):
D. Herriott, et al., Appl. Opt. 3, 523 (1964)
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
New cavity: Two double-passes through the disk Thin-film polarizer for polarization selection Herriott-type multipass cell (10 m mirror)
frep = 3 MHz Toc = 25 % 300 W single
fundamental mode
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
Soliton modelocking: Self-phase modulation (remaining
atmosphere at ≈1 mbar) 390 µrad/MW
Negative dispersion (GTI-type mirrors)
GDD = -28000 fs2 per roundtrip
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
SESAM with multiple QW and dielectric topcoating for high damage threshold#1
- Fsat = 120 μJ/cm2
- ΔR = 1.1 % - ΔRns = 0.1 % #1 C.J. Saraceno, et al., IEEE JSTQE, vol 18, no.1, pp 29-41 (2012)
Energy scaling
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Laboratoire Temps – Fréquence (LTF)
➝ Highest pulse energy from any ultrafast oscillator
Pavg = 242 W τp = 1070 fs
Ppump = 790 W ηopt = 30 % frep = 3.03 MHz M2 < 1.05 EP = 80 µJ τP∙Δν = 0.39 Ppk = 66 MW (ideal: 0.315)
Results
C. Saraceno, F. Emaury, C. Schriber, M. Hoffmann, M. Golling, T. Südmeyer, U. Keller, Optics Letters, 39, 9 (2014)
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
Calculated propagation in the fiber
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 time (ps)
wavelength (nm) 980 1030 1080
pow
er (a
.u)
spec
tral
inte
nsity
phase
Time domain
Frequency domain
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
Calculated propagation in the fiber
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2 time (ps)
wavelength (nm) 980 1030 1080
pow
er (a
.u)
spec
tral
inte
nsity
phase
Time domain
Frequency domain
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
T. Südmeyer, F. Brunner, E. Innerhofer, R. Paschotta, K. Furusawa, J. C. Baggett, T. M. Monro, D. J. Richardson, and U. Keller, "Nonlinear femtosecond pulse compression at high average power levels by use of a large-mode-area holey fiber," Opt. Lett. , vol. 28, 1951-1953 (2003).
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Laboratoire Temps – Fréquence (LTF)
First pulse compression of an ultrafast TDL (2003)
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Laboratoire Temps – Fréquence (LTF)
Yb:YAG Yb:YAG
Pav 275 W 242 W
τp 583 fs 1.07 ps
Ep 17 µJ 80 µJ
Pp 25 MW 66 MW
For most targeted scientific applications
→ Shorter pulses < 100 fs are required
Compression in gas-filled HC-PCF
Compression of few µJ level pulses to sub-50 fs at 4 MHz F. Emaury et al, Optics Express 21, 4986 (2013)
Compression/transmission of mJ level pulses at 1 kHz C. Fourcade Dutin et al, Postdeadline Paper CTh5C.7 CLEO US 2013
Compression of 40 µJ level pulses at 3 MHz (100 W)
Pulse compression today
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Laboratoire Temps – Fréquence (LTF)
Available at fiber launch: Pav = 150 W Ep = 50 µJ frep = 3 MHz τp = 1.1 ps
Pulse compression
Florian Emaury, Clara J. Saraceno, Benoit Debord, Debashri Ghosh, Andreas Diebold, Frederic Gerome, Thomas Südmeyer, Fetah Benabid, and Ursula Keller, “Efficient Pulse Compression in the 100-W Average Power Regime Using Gas-Filled Kagome Hollow-Core Photonic Crystal Fibers” Optics Letters Vol. 39, Issue 24, pp. 6843–6846 (2014)
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Laboratoire Temps – Fréquence (LTF)
Fiber: • Kagome-type HC-PCF 7-
cell hypocycloid core • MFD ≈ 30 µm • Ar-filled: 5 bar • Length = 67 cm
Transmission 92% at maximum power 134 W out for 144 W launched: highest value through Kagome
Pulse compression
Available at fiber launch: Pav = 150 W Ep = 50 µJ frep = 3 MHz τp = 1.1 ps
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Laboratoire Temps – Fréquence (LTF)
Compression with 80% total power efficiency Output: 100 W compressed to sub-200 fs
Expected soon: sub-50 fs, better compression efficiency with chirped mirrors
123 W 41 µJ 1.2 ps
Pulse compression
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
F. Brunner, E. Innerhofer, S. V. Marchese, T. Südmeyer, R. Paschotta, T. Usami, H. Ito, S. Kurimura, K. Kitamura, G. Arisholm, and U. Keller, “Powerful red-green-blue laser source pumped with a mode-locked thin disk laser,” Opt. Lett. 29, 1921-1923 (2004).
• Pump source: ultrafast thin disk laser
1030 nm
thin disk laser
Efficient RGB system pumped by a TDL (1.4 µJ, 780 fs)
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Laboratoire Temps – Fréquence (LTF)
F. Brunner, E. Innerhofer, S. V. Marchese, T. Südmeyer, R. Paschotta, T. Usami, H. Ito, S. Kurimura, K. Kitamura, G. Arisholm, and U. Keller, “Powerful red-green-blue laser source pumped with a mode-locked thin disk laser,” Opt. Lett. 29, 1921-1923 (2004).
• Pump source: ultrafast thin disk laser • RGB setup
• second-harmonic generation (SHG)
515 nm 1030 nm
thin disk laser SHG
1030 nm
Efficient RGB system pumped by a TDL (1.4 µJ, 780 fs)
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Laboratoire Temps – Fréquence (LTF)
F. Brunner, E. Innerhofer, S. V. Marchese, T. Südmeyer, R. Paschotta, T. Usami, H. Ito, S. Kurimura, K. Kitamura, G. Arisholm, and U. Keller, “Powerful red-green-blue laser source pumped with a mode-locked thin disk laser,” Opt. Lett. 29, 1921-1923 (2004).
• Pump source: ultrafast thin disk laser • RGB setup
• second-harmonic generation (SHG) • two-stage OPG
• optical parametric generation (OPG) • optical parametric amplification (OPA)
RGB
515 nm 1030 nm 799 nm
thin disk laser
two-stage OPG SHG
515 nm 1030 nm
1450 nm
Efficient RGB system pumped by a TDL (1.4 µJ, 780 fs)
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Laboratoire Temps – Fréquence (LTF)
F. Brunner, E. Innerhofer, S. V. Marchese, T. Südmeyer, R. Paschotta, T. Usami, H. Ito, S. Kurimura, K. Kitamura, G. Arisholm, and U. Keller, “Powerful red-green-blue laser source pumped with a mode-locked thin disk laser,” Opt. Lett. 29, 1921-1923 (2004).
• Pump source: ultrafast thin disk laser • RGB setup
• second-harmonic generation (SHG) • two-stage OPG
• optical parametric generation (OPG) • optical parametric amplification (OPA)
• two sum frequency mixers (SFM)
RGB
515 nm 1030 nm 799 nm 1450 nm
450 nm
thin disk laser
two-stage OPG SHG SFM
red
603 nm 515 nm
SFM blue
1030 nm
1450 nm
Efficient RGB system pumped by a TDL (1.4 µJ, 780 fs)
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Laboratoire Temps – Fréquence (LTF)
F. Brunner, E. Innerhofer, S. V. Marchese, T. Südmeyer, R. Paschotta, T. Usami, H. Ito, S. Kurimura, K. Kitamura, G. Arisholm, and U. Keller, “Powerful red-green-blue laser source pumped with a mode-locked thin disk laser,” Opt. Lett. 29, 1921-1923 (2004).
• Pump source: ultrafast thin disk laser • RGB setup
• second-harmonic generation (SHG) • two-stage OPG
• optical parametric generation (OPG) • optical parametric amplification (OPA)
• two sum frequency mixers (SFM)
RGB
515 nm 1030 nm 799 nm 1450 nm
450 nm
thin disk laser
two-stage OPG SHG SFM
red
603 nm 515 nm
SFM blue
1030 nm
1450 nm
Efficient RGB system pumped by a TDL (1.4 µJ, 780 fs)
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Laboratoire Temps – Fréquence (LTF)
Pavg = 79 W Ep = 1.39 µJ τp = 780 fs Ppeak = 1.57 MW frep = 56.8 MHz τp ∆ν = 0.37 M 2 < 1.2 linearly polarized
autocorrelation optical spectrum
Time delay (ps)
τp = 780 fs
Wavelength (nm)
1.67 nm
Pump source: modelocked TDL
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Laboratoire Temps – Fréquence (LTF)
mode-locked thin disk laser
SHG in LBO
79 W
1030 nm
515 nm
up to 48 W at 515 nm (66% conversion efficiency)
pump power @ 1030 nm (W)
SHG
pow
er (W
) w1030 = 150 µm
• 5-mm long LBO crystal • critically phase-matched • at room temperature
Second Harmonic Generation
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Laboratoire Temps – Fréquence (LTF)
Generation of blue and red color by sum frequency mixing of
1030 nm + 799 nm 450 nm 1030 nm + 1450 nm 603 nm
requires multi-watt power at 799 nm and 1450 nm
How to get red and blue?
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Laboratoire Temps – Fréquence (LTF)
• optical parametric oscillator (OPO) • active stabilization of cavity length required
#) T. Südmeyer et al., Opt. Lett. 26, 304 (2001)
• fiber-feedback optical parametric oscillator #)
• feedback through a single mode fiber • no active stabilization required
• optical parametric generator (OPG) • only few optical components • OPG at high repetition rates
• femtosecond pulses with up to 2.5 W *)
• picosecond pulses with up to 9.5 W †)
*) T. Südmeyer et al., CLEO (2002), Talk CTuO4 †) B. Köhler et al., Appl. Phys. B 75, 31 (2002)
Flexible wavelength conversion
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Laboratoire Temps – Fréquence (LTF)
Gain guiding in high-gain parametric devices:
nonlinear crystal
• highest conversion takes place at crystal end • gain guiding reduces signal radius:
signal radius << pump radius in power amplifier section
G. Arisholm, R. Paschotta, T. Südmeyer, JOSA B 21 (3), 578 (2004)
preamplifier section power amplifier section
pump signal
Challenges for efficient high power OPG
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Laboratoire Temps – Fréquence (LTF)
Pump depletion causes „hole” in pump profile
Consequence: trade-off between conversion efficiency and beam quality in high-gain processes
Conversion efficiency
M2 fa
ctor
of s
igna
l
Position (mm)
Nor
m. F
luen
ce pump in
pump out
low gain situation
pump in pump out
Position (mm)
Nor
m. F
luen
ce
high gain situation
Challenges for efficient high power OPG
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Laboratoire Temps – Fréquence (LTF)
reliable operation with multi-watt power at 799 nm and 1450 nm and good beam quality
Solution: two-stage approach: • first stage: OPG with limited pump depletion
(Note: conversion efficiency not important) • second stage: OPA with good conversion efficiency,
but limited gain ( weak gain guiding)
first stage : OPG second stage: OPA
• seed wave generated • limited pump depletion
• optimized mode areas • limited gain
1030 nm 1450 nm 799 nm
1450 nm
PPSLT LBO
515 nm
Challenges for efficient high power OPG
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Laboratoire Temps – Fréquence (LTF)
mode-locked thin disk laser
SHG in LBO
1030 nm
1030 nm
λ/2
1450 nm
OPG in PPSLT
79 W
1030 nm
515 nm OPG in PPSLT 8W@1030 nm ⇒ 1.6W@1450 nm + 3556 nm
double-pass in uncoated 17.5-mm PPSLT (150 °C, 29 µm period)
OPG in PPSLT
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Laboratoire Temps – Fréquence (LTF)
mode-locked thin disk laser
SHG in LBO
OPA in LBO
799 nm
1030 nm
1030 nm
1450 nm λ/2
515 nm 1450 nm
OPG in PPSLT
23 W 515-nm
79 W
42 W
1030 nm
515 nm
OPA 515 nm + 1450 nm
• amplification of 1450 nm, generation of 799 nm • 10-mm long LBO crystal • critically phase-matched (20°C)
1.6 W
1450 nm: 7 W, 1.2 ps 799 nm: 12 W, 0.7 ps
OPA in LBO
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Laboratoire Temps – Fréquence (LTF)
mode-locked thin disk laser
SHG in LBO
OPA in LBO
SFM in LBO
1030 nm
799 nm
1030 nm
1030 nm
1450 nm λ/2
515 nm 1450 nm
OPG in PPSLT
450-nm
515-nm
79 W
42 W
23 W 1030 nm
515 nm
Sum frequency mixing
23 W
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Laboratoire Temps – Fréquence (LTF)
603-nm mode-locked thin disk laser
SHG in LBO
OPA in LBO
SFM in LBO
1030 nm
799 nm
1030 nm
1030 nm
1450 nm λ/2
515 nm 1450 nm
OPG in PPSLT
450-nm
515-nm
79 W
SFM in LBO
42 W
23 W 1030 nm
515 nm
Sum frequency mixing
23 W
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Laboratoire Temps – Fréquence (LTF)
• 15-mm long LBO crystal • nearly non-critically phase-matched at room temperature
SFM: 1030 nm + 1450 nm 603 nm
Spe
ctra
l Int
ensi
ty (a
.u.)
1.1 nm
Wavelength (nm)
603-nm output: Pavg = 8 W M 2 = 1.1
• 10-mm long LBO crystal • critically phase-matched at room temperature
SFM: 1030 nm + 799 nm 450 nm
0.6 nm
Spe
ctra
l Int
ensi
ty (a
.u.)
Wavelength (nm)
450-nm output: Pavg = 10.1 W
M 2 = 1.1
Sum frequency mixing
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Laboratoire Temps – Fréquence (LTF)
603-nm 8 W mode-locked
thin disk laser
SHG in LBO
OPA in LBO
SFM in LBO
1030 nm
799 nm
1030 nm
1030 nm
1450 nm λ/2
515 nm 1450 nm
OPG in PPSLT
450-nm 10.1 W
515-nm
79 W
SFM in LBO
42 W
23 W 1030 nm
515 nm
Experimental setup
23 W
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Laboratoire Temps – Fréquence (LTF)
µJ pulses with ∼1 ps are well-suited for efficient RGB generation
• OPG-based: no synchronized cavities • Simple system design • Optimal operation Yb-YAG TDLs
Latest generation TDL with 275 W ⇒ expect >30 W per color
RGB output Pavg @ 603 nm = 8.0 W Pavg @ 515 nm = 23.0 W Pavg @ 450 nm = 10.1 W pulse durations ≈ 1 ps
Ultrafast thin disk laser DPSSL Pavg @ 1030 = 80 W repetition rate = 57 MHz
RGB output
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
BUT: never used for projection… However, other lasers did
(Sony Annual Report 20015)
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
Sony Laser Dream Theater at the Aichi Expo 2005
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
Sony Laser Dream Theater at the Aichi Expo 2005
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
Sony Laser Dream Theater at the Aichi Expo 2005
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
BUT: never used for projection… However, other lasers did
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Laboratoire Temps – Fréquence (LTF)
http://www.sony.net/Products/SC-HP/cx_news/vol40/pdf/sideview40.pdf
BUT: never used for projection… However, other lasers did
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Laboratoire Temps – Fréquence (LTF)
Green laser: optically-pumped VECSEL (OSRAM) Ulrich Steegmueller et al., “Progress in ultra-compact green frequency doubled optically pumped surface emitting lasers”, High-Power Diode Laser Technology and Applications VII, Proc. of SPIE Vol. 7198 719807, 2009 H. Lindberg et al., “Recent advances in VECSELs for laser projection applications”, Vertical External Cavity Surface Emitting Lasers (VECSELs), Proc. of SPIE Vol. 7919 79190D, 2011
less than 0.4cm3 >70 mW green
Microvision laser projector
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
• >20 W green • 88% external efficiency • M²=1.00x1.03
T. Südmeyer, Y. Imai, H. Masuda, N. Eguchi, M. Saito, and S. Kubota, “Efficient 2nd and 4th harmonic generation of a single-frequency, continuous-wave fiber amplifier”, Opt. Express, 1546 (2008)
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
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Laboratoire Temps – Fréquence (LTF)
Nonlinear UV generation
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Laboratoire Temps – Fréquence (LTF)
Overview
Ultrafast lasers Ultrafast high power lasers Nonlinear temporal pulse compression Nonlinear high power frequency conversion: an RGB system for laser projection Nonlinear UV generation Nonlinear VUV/XUV generation
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Laboratoire Temps – Fréquence (LTF)
Optics and Photonics News, Vol. 19, Issue 10, pp. 24-29 (2008) http://dx.doi.org/10.1364/OPN.19.10.000024
⇒ until 2000: limited to fs regime Pulses generated directly out of laser oscillators operating in VIS/IR spectral region.
Pulse duration of ultrafast sources
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Laboratoire Temps – Fréquence (LTF)
Optics and Photonics News, Vol. 19, Issue 10, pp. 24-29 (2008) http://dx.doi.org/10.1364/OPN.19.10.000024
Attosecond pulses High harmonic generation of intense fs-pulses results in as-pulses in VUV/XUV spectral regime
Pulse duration of ultrafast sources
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Laboratoire Temps – Fréquence (LTF)
infrared fs-pulses
XUV
light intensity 1013-1015 W⋅cm-2
gas target
IR beam block
E.A. Gibson, Science 302, 98 (2003)
Extreme nonlinear up-conversion of IR fs-pulses in gas target • broad range of coherent UV-XUV radiation • attosecond duration
HHG: bringing coherent XUV light to the lab
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Laboratoire Temps – Fréquence (LTF)
infrared fs-pulses
XUV
light intensity 1013-1015 W⋅cm-2
gas target
IR beam block
E.A. Gibson, Science 302, 98 (2003)
Slide 4
Limitations • conversion efficiency 10-8 to 10-6 • typical fs-amplifier: 10 W, 1 kHz
flux too low for many applications kHz repetition rate:
no frequency combs, limited usefulness
HHG: bringing coherent XUV light to the lab
Extreme nonlinear up-conversion of IR fs-pulses in gas target • broad range of coherent UV-XUV radiation • attosecond duration
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HHG in enhancement cavities
Jones, et al., Phys Rev. Lett. 94, 193201 (2005) Gohle, et al., Nature 436, 234 (2005)
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ERC MegaXUV: intra-laser high harmonic generation
laser gain
XUV
passive pulse formation
gas target
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Minimum pulse duration of Yb-doped bulk lasers and TDLs
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Average power and intracavity peak power of ultrafast TDLs
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IIBS Coatings
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Expect: Numerous applications in the area of NLO
→ Pulse compression to few-cycle pulses at 100s W average power
→ HHG, Intra-laser HHG, UV generation, Mid-IR generation, THz generation, ...
Expect: higher pulse energy > 100 µJ and higher average power > 1000 W
→ Longer cavities, spot size scaling, novel SESAM designs, better dispersive mirrors, …
TDLs achieve highest energy & power from ultrafast oscillators
→ Succesful energy scaling in vacuum environment: 80 µJ, 242 W, 1.07 ps, 3 MHz
Pulse compression at high energy in Kagome HC-PCFs
→ 100 W compressed with sub-200 fs pulses with 80% total compression efficiency
Excellent stability
→ CEO stabilization of TDL achieved (see talk tomorrow)
Conclusion: high power thin disk laser oscillators & NLO
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Acknowledgments
ETH ULP group of Prof. Ursula Keller
UniNE LTF group