MIXSEL2 - Nano-Tera 2016
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Transcript of MIXSEL2 - Nano-Tera 2016
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Vertical integration of
ultrafast semiconductor lasersand their applicationsnano-tera.ch
Prof. Ursula Keller (PI)
Dr. Matthias Golling
Sandro Link
Dominik Waldburger
Cesare Alfieri
Prof. Thomas Südmeyer
Dr. Stephane Schilt
Dr. Valentin Wittwer
Nayara Jornod
Dr. Jacques Morel
Dr. Laurent Devenoges
Dr. Deran Maas
Dr. Thomas Paul
Dr. Gábor Csúcs
II
Start MIXSEL II: 1. Nov. 2013 (current review after 2.5 years)
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Outline
1) Requirements for stabilized frequency combs
based on modelocked lasers
2) New gigahertz frequency comb sources
1) Diode-pumped Yb-doped solid-state lasers
2)
Frequency comb stabilization with PCFs3) Frequency comb stabilization with Si3N4
3) New gigahertz frequency comb sources
1) Semiconductor thin disk lasers: VECSELs, MIXSELs2) Dual comb modelocked lasers
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Laser pulse as a superposition of many frequencies
• A continuous wave laser emits in one or only few frequencies
• Typical femtosecond laser pulse trains are generated with a
superposition of millions of single frequencies (1 femtosecond = 10-15 s)• Single frequencies are phase locked with intracavity modulator
(or saturable absorber): “modelocking”
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Magnification: 100'000 x
Modelocked laser can give a „frequency ruler“
Magnification:
100'000 x ! Spectrum of a fs modelocked laser consists of millions of fine lines
! Line spacing is given by pulse repetition frequency f rep:
!t =1
f rep
Line spacing was stabilized in the 1980’s:referred to as “timing jitter stabilization”
Patent D. Cotter (1985, British Telecom)
Actively modelocked flashlamp-pumped Nd:YAG laser (1986)M. J. W. Rodwell, D. M. Bloom, K. J. Weingarten, IEEE J. Quantum Electr. 25, 817, 1989
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Magnification: 100'000 x
Modelocked laser can give a „frequency ruler“
Magnification:
100'000 x ! Spectrum of a fs modelocked laser consists of millions of fine lines
! Femtosecond laser is for frequency the same as a ruler for length:
!
.... but the „zero“ of the frequency ruler was not stabilized!
Solution given how to stabilize the zero of the frequency ruler:
H.R. Telle, G. Steinmeyer, A. E. Dunlop, J. Stenger, D. H. Sutter, U. Keller
Appl. Phys. B 69, 327 (1999)
! Line spacing is given by pulse repetition frequency f rep and can be stabilized
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T = 2.7 fs @800 nm
Ultrashort pulse generation
1as
Time
F
W
H
M
p
s
e
w
d
h
s
e
20001990198019701960
ear
10 fs
100 fs
1 ps
1 fs
10 ps
Ti:sapphire laser!5.5 fs with !200 mW
dye laser27 fs with !10 mW
compressed
Science 286, 1507, 1999
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Carrier Envelope Offset (CEO)
frequency
f CEO
f n = n f rep + f CEO
H.R. Telle, G. Steinmeyer, A.E. Dunlop, J. Stenger, D.H. Sutter and U. Keller, Appl. Phys. B 69, 327 (1999)
0
t
Mode-locked pulse train
Pulse envelope
A(t )
! c = 2.7 fs @800 nm
CEO phase
f CEO =!"
0
2# T R
!" 0T R =
1
f rep
E t ( ) = A t ( )exp i! ct + i" 0 (t )( )
Electric field
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f rep : pulse repetition rate frequency , f CEO : carrier envelope offset frequency
How can we measure the frequency comb offset ?
f rep
f CEO = 2 f 1 – f 2
f CEO
f 2 2f 1
2f 1 = 2 f CEO + 2n f rep
f 2 = f CEO + 2n f rep
f 1
f 1 = f CEO + n f rep
octave spanning modelocked spectrum
Mode beating of fundamental and second harmonic frequency comb f -to-2f interference technique: f CEO = 2 f 1 – f 2
H.R. Telle, G. Steinmeyer, A.E. Dunlop, J. Stenger, D.H. Sutter and U. Keller, Appl. Phys. B 69, 327 (1999)
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Frequency combs from modelocked lasers
unlocked repetition rate: f rep unlocked CEO: f CEO time average
free-running passively modelocked laser
! Femtosecond laser is for frequency the same as a ruler for length:
!
.... but the „zero“ of the frequency ruler was not stabilized!
Solution given how to stabilize the zero of the frequency ruler:
H.R. Telle, G. Steinmeyer, A. E. Dunlop, J. Stenger, D. H. Sutter, U. Keller
Appl. Phys. B 69, 327 (1999)
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Optical Frequency Combs
THz
MHz
undefined, optical
frequency
frequency
intensity
phase-stable link:
optical to microwave
intensity
frequency
beat
frequency
intensity f rep, low
f rep, high
High gigahertz pulse repetition rate frequency combs:
• higher power per mode
•
easier to access individual lines• more compact laser system
GHz
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GHz oscillators w/o amplification or compression
most recentmultimode
pump diode
Yb:CALGO
SESAMoutput
coupler
1-GHz cavity
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f rep
= 1.8 GHz = 59.4 fs
P av = 3.0 W P pk = 24.3 kW
= 1059.7 nm
Combine ultrashort pulses & high power
!"#$ &'()
#$*(+
,"!
-
Self-starting modelocking
Reliable & robust pumping
Compact & stable cavity
A. Klenner et al., Opt. Express, vol. 22, no. 9, pp. 11884-11891, 2014
! p
! 0
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Si3N4 waveguide
Substrate: Oxide-clad Silicon
Top-Cladding: SiO2
Cross section: 690 nm x 900 nm
Length: 7.5 mm
Bend radius: > 100 !m
Nonlin. coeff.: " = 3.25 W-1m-1 @1055 nmD. J. Moss, R. Morandotti, A. L. Gaeta, and M.Lipson, Nature Photon. 7, 597-607 (2013)
Silicon Nitride (Si3N4)
• VIS to 6 !m, negligible two-
photon absorption at 1 !m
• 10 times higher nonlinear index n2than silica
• CMOS-compatible
600 800 1000 1200 1400 1600
−60
−40
−20
0
wavelength (nm)
s p e c t r a l p o w e r ( d B c )
36 pJ
one octave2f f
680 nm 1360 nm
A. S. Mayer, A. Klenner, A. R. Johnson, K. Luke, M. R. E. Lamont, Y. Okawachi, M. Lipson, A. L. Gaeta, U. Keller,Opt. Express 23, 15440-15451 (2015)
0 0.2 0.4 0.6 0.8 1
−80
−
70
−60
−50
−40
−30
−20
−10
0
frep= 1.025 GHzRBW = 30 kHz f
CEO,1 f
CEO,2
frequency (GHz)
a m p l i t u d e ( d B c )
> 40 dB
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Benefits of Si3N4 waveguide
multimode
pump diode
Yb:CALGO
SESAMoutput
coupler
1-GHz cavity
p e a k p o w e r ( k W )
repetition rate (GHz)
0.34 kW
First self-referenced frequency comb based on SCG in Si3N4 Chip
Moreover:
• First CEO-Stabilization with extra-
cavity SCG requiring < 1kW
• 304 mrad: Lowest RPN of any
stabilized gigahertz diode-
pumped solid state laser to date
Towards stabilized multi-GHz DPSSLs and
Semiconductor Disk Laser
23.5 kW
.
.
.
.
.
fCEO
= 73.9 MHz
.
span = 2 MHz
RBW = 3 kHz
100 averages
−0.8 −0.4 0 0.4 0.8
−60
−50
−40
−30
−20
−10
0
frequency offset (MHz)
s p e c t r a l p o w e r ( d B c )
− −
−
−
−
−
−
−
−
−
l
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Si3N4 waveguide instead of PCFs
D. J. Moss, R. Morandotti, A. L. Gaeta, and M.Lipson, Nature Photon. 7, 597-607 (2013)
Silicon Nitride (Si3N4)
• VIS to 6 !m, negligible two-
photon absorption at 1 !m
• 10 times higher nonlinear index n2than silica
• CMOS-compatible
Vision: Full integration
p e a k p o w e r ( k W )
repetition rate (GHz)
0.34 kW
Moreover:
• First CEO-Stabilization with extra-
cavity SCG requiring < 1kW
• 304 mrad: Lowest RPN of any
stabilized gigahertz diode-
pumped solid state laser to date
Towards stabilized multi-GHz DPSSLs and
Semiconductor Disk Laser
23.5 kW
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Outline
1) Requirements for stabilized frequency combs
based on modelocked lasers
2) New gigahertz frequency comb sources
1) Diode-pumped Yb-doped solid-state lasers
2)
Frequency comb stabilization with PCFs3) Frequency comb stabilization with Si3N4
3) New gigahertz frequency comb sources
1) Semiconductor thin disk lasers: VECSELs, MIXSELs2) Dual comb modelocked lasers
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OPSLs = OP-VECSELs
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GHz oscillators w/o amplification or compression
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Overview and Highlight Laser Development
1 mW
10 mW
100 mW
1 W
10 W
Averageoutputp
ower
100 fs 1 p
Pulse duration
'VECSEls Keller'
'MIXSELs'
'VECSELs others'
100 mW
1 W
10 W
100 W
1 kW
10 kW
Peakpower
100 fs 1 ps 10 ps
Pulse duration
'Peak Power VECSELs Keller'
'Peak Power MIXSELs '
'Peak Power VECSELs others'
shorter pulses
higher peak power
Laser development
world leading andsignificant progress:
First
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1 mW
10 mW
100 mW
1 W
10 W
Averageoutputpower
100 fs 1 pPulse duration
'VECSEls Keller'
'MIXSELs'
'VECSELs others'
Highlight: First sub-100-fs VECSEL
Start
shortest pulse duration from any
fundamentally modelocked SDL
pulse duration: 96 fs
average output power: 100 mW
repetition rate: 1.64 GHz
peak power: 560 W
Todaydone
1.0
0.8
0.6
0.4
0.2
0.0norm.intensity
-400 -200 0 200 400time [fs]
4
3
2
1
0
ph a s e [ r a d ]
!p = 96.1 fs
1.0
0.8
0.6
0.4
0.2
0.0
norm.spec.intensity
1060104010201000wavelength [nm]
4
3
2
1
0
s p e c t r al ph a s e [ r a d ]
FWHM:17.5 nm
FROG OSA
-80
-60
-40
-20
0
intensity
[dBc]
6420-2-4-6offset frequency [MHz]
f rep = 1.64 GHz span: 15 MHzRBW: 100 Hz
-60
-40
-20
0
intensity
[dBc]
2015105
frequency [GHz]
RBW: 300 kHz
VECSEL:
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1 mW
10 mW
100 mW
1 W
10 W
Averageoutputpower
100 fs 1 pPulse duration
'VECSEls Keller'
'MIXSELs'
'VECSELs others'
Highlight: First sub-300-fs MIXSEL
Sub 300 fs MIXSEL any power
End of year 3 milestone already done!
pulse duration: 184 fs
average output power: 115 mW
repetition rate: 4.33 GHz
center wavelength: 1048 nm
Todaydone
1.0
0.8
0.6
0.4
0.2
0.0
autocorrelation
[arb.u.]
-400 0 400delay [fs]
4
3
2
1
0
ph a s e [ r a d ]
!p= 184 fs
1.0
0.8
0.6
0.4
0.2
0.0
spectralintensity
[arb.
u.]
1060105010401030wavelength [nm]
4
3
2
1
0
ph a s e [ r a d ]
FWHM:7.4 nm
!c=
1048.2 nm
FROG OSA
-80
-60
-40
-200
intensity
[dBc]
-4 0 4offset frequency [GHz]
span: 15 MHzRBW: 100 Hz
f rep= 4.33 GHz
-60
-40
-20
0
intensity
[dBc]
2520151050frequency [GHz]
RBW 30kHz
shortest pulse duration from a
MIXSEL
MIXSEL:
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Highlight: Invention of dual comb modelocked lasers
Patent Application:
Swiss Patent filed 2. Oct. 2014
International Patent:WO 2016/049787 A1
published 7. April 2016filed 30. Sept. 2015
First journal publication:
S. M. Link, A. Klenner, M. Mangold, C. A. Zaugg,M. Golling, B. W. Tilma, U. Keller
Optics Express 23, 5521, 2015
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OC
MIXSEL chipheatsink
etalon
OC
MIXSEL chipheatsink
etalon
birefringent
crystal
Dual-comb MIXSEL
S. M. Link, A. Klenner, M. Mangold, C. A. Zaugg, M. Golling, B. W. Tilma, U. Keller,
Optics Express, vol. 23, No. 5, pp. 5521-5531, 2015
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Dual comb MIXSEL
MIXSEL chip
heatsink
etalon
birefringent
crystal
1 Hz, 100 MHz[ ]
!16 ns
! 4 ps
??
• cavity length adjustment hasno effect on other beam
•
phase noise of two beams
sharing the same cavity is
uncorrelated
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Pulse shift on saturable absorber
time
leading edgeexperiences
absorption
pulse shifts in time each round-trip
s a t u r a b l e a b s o
r b e r
S. M. Link, A. Klenner, U. Keller“Dual-comb modelocked lasers: semiconductor saturable absorber mirror decouples noise stabilization”Optics Express, vol. 24, No. 3, pp. 1889-1902, 2016
spatial overlap temporal overlap
1 feedback loop
time706050 706050403020
time70605040 605040
spatial overlap NO temporal overlap
2 feedback loops
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Stabilization of both pulse repetition rates
Photodetector
electronic reference
phase-lockedloop circuit
f rep,1
Photodetector
#f rep-20
-10
0
amplitude[dBc]
20151050frequency [MHz]
span 20 MHzRBW 10 kHz
2!f rep
!f repDC
stabilization of f rep,1 stabilization of #f rep
electronic reference
phase-lockedloop circuit multimode
pump
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Stabilization of both pulse repetition rates
-120
-100
-80
-60-40
-20
0
20
40
phase
noise
[dBc/Hz]
10
0
10
2
10
4
10
6
10
8
offset frequency [Hz]
s-pol free-running
s-pol lock !f rep with pump
and lock p-pol f rep with piezo p-pol free-running
p-pol s-pol lock !f rep with pump
and lock p-pol f rep with piezo
phase noise MIXSEL
s-polarized beam stabilized
p-polarized beam stabilized
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MIXSEL chip
heatsink
etalon
birefringent
crystal
Conclusion
MIXSELModelocked Integrated
External-Cavity Surface
Emitting Laser
robust & reliable
cost-efficient
broadband & high power
high repetition rates
A new class of
frequency combs is evolving
MIXSEL: towards semiconductor basedfrequency combs and dual comb lasers
D. J. H. C. Maas, et al., APB 88, 493 (2007)
S. M. Link, et al.,Optics Express 23, 5521 (2015)
p e a k p o w e r ( k W )
repetition rate (GHz)
0.34 kW
Silicon Nitride (Si3N4)