Transcript Adopt_lecture_F_Laurell_part3.ppt i Powerpoint-format (5,8 MB)

High power VBG Yb-fiber laser
Pump source
at 975 nm
Output
at 1066 nm
VBG
Output power (W) 12
150
125
Slope eff. ~75 %
100
75
Δλ = 0.4 nm
M2~5.5
50
25
Yb fiber
0
0
50
100
150
200
Launched pump power (W)
Yb-fiber
Core:  30 m, NA 0.056
VBG 1.5mm 3mm 5mm
• D-shaped cladding :  400 m, NA 0.49
Δλ = 0.22 nm, λcentre = 1066.0 nm,
• Fiber length : ~8 m (abs. ~2 dB/m at 975 nm)
AR coated
• Launch efficiency : ~90 %
surface normal polished ~2o to the grating vector
P. Jelger, P. Wang, J. K. Sahu, F. Laurell, and W. A. Clarkson, Opt. Expr. 16, 9507 (2008)
R= 99 %
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Transversally chirped VBG Yb laser
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> 100 W output
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> 78 % slope efficiency
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Tunable from 1064-1073 nm
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<0.5 % power fluctuation over
tuning range
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Narrowband signal < 50 pm
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Temporal stability <0.2 % rms
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M2 = 1.2
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Single-polarization >18 dB PER
SBS threshold approx. 5 kW
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Tunable, high-power, 2 wavelength Yb laser
Dual-line lasing 78 W
wavelength separation
0.03 - 2 THz,
Power fluctuation<1 %.
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Ultra-fast lasers
Kerr-Lens ML Ti:sapphire laser
D.E. Spence, P.K. Kean, and W. Sibbet Opt. Lett. 16, 42 (1991)
M. Piché, Opt. Commun. 86, 156 (1991)
Patent for the Aperture (Coherent)
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The Frequency Comb
T
 = phase offset
between carrier wave
and wave envelope
fm = mfrep + foffset
frep= 1/T
foffset = ( /2) frep
Therefore if
 = 0  foffset= 0 
fm = mfrep
The idea has revolutionized the art of frequency measurements
Theodor W. Hänsch e John L. Hall, Nobel Prize for Physics (2005)
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High Peak Intensities Lasers
Chirped Pulse Amplification (CPA)
D. Strickland and G. Mourou (1985)
oscillator
 103 - 105
stretcher
up to 105
amplifier
 10-3 – 10-5
compressor
 Ti:Al2O3 : 1-10 mJ; f = 1-10 kHz
 TTT [Terawatt Table Top] Lasers : 100 TW (5 J, 50 fs)
 Petawatt-class Lasers (1,5 PW, i.e. 580 J and 460 fs)
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Historical Evolution of Pulse Duration
From Femtoseconds to Attoseconds
4 fs
80 as: E. Goulielmakis
et. al., Science 320,
1614 (2008)
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Everything...
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In Science
Laser cooling
Na-atom molasses
6 laser beams with frequency slightly
shorter than the transition frequency.
Reduced the energy of a cloud of atoms
to form an optical molasses.
Temperatures down to micro-Kelvin.
Nobel prize in 1997 for Chu,
Cohen-Tannoudji and Phillips
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The world's largest and highest-energy laser
the National Ignition Facility at Lawrence Livermore
In the NIF experiments 192 giant laser beams are focused on a cm-sized target filled with hydrogen fuel.
NIF's goal is to fuse the hydrogen atoms' nuclei and produce net energy gain (Eout = 100 Ein)
The beams compress the target to 100 billion times the atmosphere to a temperature of 100 million °C
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Imaging and displays – large, small or 3D
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Conclusions
Solid-state lasers
• efficient
• Reliable
• tailored
fun
And….
Acknowledgments
Friends and laser family
References can be found on
www.laserphysics.kth.se
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That´s all folks!
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Hollow fiber dye and Q-dots sources
Scematic layout
Photograph of
Rodamine 6G
filled fiber
Green pumped hollow fibre in wich dye is pumped
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Functional optical materials and structures
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Chemically and photostructured glasses
Domain engineered ferroelectrics
Quantum dots
Silicone elastomers
Microstructured silicon
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Acknowledgments
Laser physics group
National and
international colleagues
www.laserfest.org
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Limitations related to thermal loading
2 mm
1 kW
5 mm
Absorption 0.2%/cm
Δ λ ~ 0.5 nm
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Chirp reduces reflectivity!
VBG would transmit more
power!
Width of VBG [mm]
FEM simulation
Temperature
distribution
Distance into VBG [mm]
Significant problem for low gain lasers
and high circulating powers
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> 30 W Single Frequency CW VBG OPO
P. Zeil, et al. Optics Express, 22, 29907-29913 (2014).
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