outline - kth.se/adopt_lecture... · 44! outline part ii ! femtosecond to attosecond precision...
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44!
Outline Part II
! Femtosecond to attosecond precision timing distribution for large scale facilities: Example X-ray FEL
! Synchronization system layout for a seeded X-ray FEL
! Advantages of a pulsed optical distribution system
! Timing jitter of femtosecond lasers
! Timing distribution over stabilized fiber links
! Optical-to-optical synchronization
! RF-Extraction and locking to microwave references
! Outlook: Photonic ADCs!
45!
Next Generation X-ray Source Schematic
Today long-term sub-10 fs synchronization over entire facility desired. 300 m - 3 km
Tomorrow sub-fs synchronization will be required.
fs x-ray pulses
Seeding with various schemes demonstrated: For lasers the challenge comes with high repetition rates
(Seeded, high repetition rate X-Ray FELs)
46!
Pulsed femtosecond timing distribution
J. Kim et al, FEL 2004.
fs x-ray pulses
Other approaches: R. Wilcox, LBNL, cw-distribution, or post stamping
47!
10 -6
Femtosecond Laser!
TR
time!
τ"
Δt Optical Cavity
Electronic Oscillator!
time!
ampl
itude! T0 Δt
Timing jitter of femtosecond lasers!
J. Kim et al., Laser & Phot. Rev., 1–25 (2009). H. A. Haus et al., IEEE JQE 29, 983 (1993).
10 -4
kTc 50~ω!
2 2 1 cML
pulse cav
d tdt W
ωτ
τ< Δ >≈ ⋅ ⋅
h
pulse width ~100fs
ħωc = photon energy
Dissipation-Fluctuation!Theorem!
2 20
mod
1RF
e cav
d kTt Tdt W τ< Δ >≈ ⋅ ⋅
cavity lifetime
period ~100ps
kT = thermal energy
48!
Why Optical Pulses (Mode-locked Lasers)?
! Real marker in time and RF domain, every harmonic can be extracted at the end station.
! Suppress Brillouin scattering and undesired reflections. ! Optical cross correlation can be used for link stabilization or for optical-
to-optical synchronization of other lasers. ! Pulses can be directly used to seed amplifiers, EO-sampling, …. ! Group delay is directly stabilized, not optical phase delay. ! After power failure system can auto-calibrate!
frequency
… ...
fR 2fR NfR
TR = 1/fR
time
Single-Crystal Balanced Cross-Correlator
49!
Reflect fundamental Transmit SHG Transmit fundamental
Reflect SHG
Type-II phase-matched PPKTP crystal
J. Kim et al., Opt. Lett. 32, 1044 (2007)
T. Schibli et al, OL 28, 947 (2003)
Single-Crystal Balanced Cross-Correlator
50!
Reflect fundamental Transmit SHG Transmit fundamental
Reflect SHG
Type-II phase-matched PPKTP crystal
Single-Crystal Balanced Cross-Correlator
51!
Reflect fundamental Transmit SHG Transmit fundamental
Reflect SHG
Type-II phase-matched PPKTP crystal
Single-Crystal Balanced Cross-Correlator
52!
In comparison: Typical microwave mixer Slope ~1 µV/fs @ 10 GHz Greatly reduced thermal drifts!
80 pJ, 200 fs 1550nm input pulses at 200 MHz rep. rate
J. Kim et al., Opt. Lett. 32, 1044 (2007)
200 MHz Soliton Er-fiber Laser
53!
• 167 fs pulses
• 200 pJ intracavity pulse energy
• 50% loss
ISO
PBS
λ/4
λ/2
λ/4
collimatorcollimator
WDM980 nm Pump
10 cmSMF
50 cmEr doped fiber 10 cm
SMF
10 cmSMF
10 cmSMF
ISO
PBS
λ/4
λ/2
λ/4
collimatorcollimator
WDM980 nm Pump
10 cmSMF
50 cmEr doped fiber 10 cm
SMF
10 cmSMF
10 cmSMF
J. Chen et al, Opt. Lett. 32, 1566 (2007).
Timing Jitter of Fiber Lasers
54!
Modelocked Laser 1
Modelocked Laser 2
HWP
PBS Single crystal balanced
cross- correlator
Oscilloscope
RF-pectrum analyzer
-1
0
1
-800 0 800
Time delay (fs)D
ete
cto
r outp
ut
(V)
Loop filter
J. Kim, et al. , Opt. Lett. 32, 3519 (2007).
Phase detector method ! Timing Detector method
103 104 105 106 107 108
10-12
10-10
10-8
10-6
10-4
10-2Ji
tter S
pect
ral D
ensi
ty (f
s2 /H
z)
103 104 105 106 107 1080
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Jitte
r (fs
rms)
Timing Jitter in Stretched Pulse Lasers
55!
! 3 fs rms [100 kHz, 40 MHz] ! Additional noise present at frep/2 and frep/4
80 MHz Er-fiber Stretched Pulse Laser
Frequency (Hz)
model
J. Cox et al. Opt. Lett., 35, 3522 (2010)
Attosecond Timing ?
56!
How do we get to Attosecond Jitter Lasers?
Intracavity losses down (Factor of 50)
Intracavity energy up (Factor of 50)
10-fs pulses (Factor of 100)
2 2 1 cML
pulse cav
d tdt W
ωτ
τ< Δ >≈ ⋅ ⋅
h
~ 106 Is it true?
Solid-state lasers
Two 10-fs Ti:Sapphire Lasers Synchronized within 13 as
57!
13 as
Ref @ 10 GHz
A. Benedick, et al. Nat. Photonics 6, 97-100, 2012
Timing jitter of OneFive:Origami Laser
58!
1k 10k 100k 1MFrequency (Hz)
Jitte
r Spe
ctra
l Den
sity
(fs2 /H
z)
10-9
Pha
se N
oise
@ 1
0GH
z (d
Bc/
Hz)
-180
10-7
10-5
10-3
-160
-140
-120
Inte
grat
ed J
itter
at [
f,1M
Hz]
(fs)
0
0.1
0.2
0.3
f > 15 kHz
K. Safak et al., Struct. Dyn. 2, 041715 (2015)
59!
Timing - Stabilized
Fiber Links
60!
Timing-stabilized fiber links
PZT-based fiber stretcher
Mode-locked laser
Fiber link ~ several hundreds meters
to a few kilometers SMF/DCF
isolator
Timing Comparison
Faraday rotating mirror
Cancel fiber length fluctuations slower than the pulse travel time (2nL/c).
1 km fiber: travel time = 10 µs ! ~100 kHz BW
1-week operation with SMF/DCF
61!
0 50 100 150-5
0
5
10
15
20
25
Tim
ing
Link
Drif
t (fs
)
Time (hours)0 50 100 150
-15
-10
-5
0
5
10
15
Fibe
r Flu
ctua
tions
(ps)
Timing Link System Performance
5 fs (rms) drifts over one week of operation
FLASH, FERMI, and tests at PAL and LCLS (2008-2014)
62!
Clocking the European XFEL
3.5 km
Injector laser�Probe laser�
M. Y. Peng et al. Opt. Exp. 21, 19982 (2013).
High precision PM-link developed jointly with OFS
Dispersion-compensating PM Fiber D = -102.5 ps/nm·km @1550nm, slow axis D’ = -0.33 ps/nm2·km, slow axis
Splice
Fiber 1 Std. PM 1550 Length: 4m
Fiber 2 Std. PM 1550
Length: 2946m
Fiber 3 Bridge Fiber Length: 2m
Fiber 4 PM DCF
Length: 511m
Fiber 5 Bridge Fiber Length: 2m
Fiber 6 Bridge Fiber Length: 19m
Fiber 7 Std. PM 1550 Length: 3m
63!
High precision PM-link results (OFS)
3.5 km
Injector laser�Probe laser�
0 4 8 12 16 20 24 28 32-1
-0.5
0
0.5
1
Out
loop
Drif
t (fs
)
36 40 44
0 4 8 12 16 20 24 28 32Time (hours)
36 40 4444454647
50
Rel
.Tem
pera
ture
(K)
-0.6-0.4-0.2
0
0.6
Rel
. Hum
idity
(%)
0.20.4
4849
Laser-to-Laser Remote Synch.: 100 as RMS & 0.6 fs Pk-Pk drift (< 1Hz) over 44 h
M. Xi et al. Opt. Exp. 22, 14904 (2014) M. Y. Peng et al. Opt. Exp. 21, 19982 (2013)
64!
Optical-to-Optical Synchronization
65!
Ti:sapphire Laser + Cr:Forsterite Laser
Ti:sapphire Cr:forsterite
Spanning over 1.5 octaves
5fs 30 fs
65!
66!
Sub-femtosecond Residual Timing Jitter
J. Kim et al, EPAC 2006.
Long-term drift-free sub-fs timing synchronization over 12 hours
Balanced optical cross-correlator based on GDD (T. Schibli et al, OL 28, 947 (2003))
67!
Optical-to-RF Conversion or
Optical-to-RF Locking
Excess Phase Noise in Photo Detection
68!
RF frequency
… ...
fR 2fR nfR
TR = 1/fR
time Photodetector
t
TR/n (E. N. Ivanov et al, IEEE JQE 2003, IEEE UFFC 2005 and 2007)
It is difficult to stabilize the phase of microwave signals To better than 10 fs precision over many hours or days of operation.
Thermal phase drift (~350 fs/K), B. Lorbeer et al, PAC 2007 Amplitude-to-phase conversion (~ ps/mW)
Balanced Optical-Microwave Phase Detector
69!
Microwave Signal
Electro-optic sampling of microwave signal with optical pulse train
Passive Lasergyro for Navigation Systems
Convert Phase /Timing information in optical domain into intensity modulation
(BOM-PD)
Optical Pulse Train
DC current
J. Kim et al., Opt. Lett. 29, 2076 (2004), 31, 3659 (2006).
Optoelectronic Phase-Locked Loop (PLL)
70!
Regeneration of a high-power, low-jitter and drift-free microwave signal whose phase is locked to the optical pulse train.
Balanced Optical-Microwave Phase Detector (BOM-PD) Regenerated
Microwave Signal Output
Tight locking of modelocked laser to microwave reference
Balanced Optical-Microwave Phase Detector (BOM-PD) Stable Pulse
Train Output
Modelocked Laser
71!
BOM-PD 1: timing synchronization BOM-PD 2: out-of-loop timing characterization
Stability of BOM-PDs
J. Kim et al., Optics Express 15, 8951 (2007).
72!
RMS timing jitter integrated in 27 µHz – 1 MHz: 6.8 fs
J. Kim et al., Nature Photonics 2, 733 (2008).
Long-term stability: 6.8 fs drift over 10 hours
~ rf-stability 2 10-19 .
CONFiDENTiAL+ 73)
< 1 fs synchronization of Laser and RF-Networks
Timing Distribution Systems Ultrashort Pulse Synchronization
DESY Spin-Off Company Products: Timing & Synchronization
• Accelerators and X-ray Free-Electron Lasers • Ultrafast Laser Labs • Radio Telescopes • Jitter Characterization • Low Noise Microwave Generation
Laser-Microwave Synchronization
< 1 fs Synchronisation of two femtosecond lasers
< 1 fs Synchronisation of microwave sources
to lasers
00 TΔt2π
VΔV
=N23
1⋅
=
Voltage!
time!
T!o!
Δt!V!o!
ΔV!
Challenge in High-Speed ADCs
Targeted resolution
10 GHz
50 GHz 14-bit 0.5 fs 0.1 fs 12-bit 2 fs 0.4 fs 10-bit 9 fs 1.8 fs 8-bit 36 fs 7.2 fs 6-bit 144 fs 30 fs
Required sampling jitter
0TΔt2π 3 2N
=⋅
74!
Photonic ADCs
104 105 106 107 108 109 1010 101102468
101214161820
this
0.1 fs
work
1 fs10 fs
100 fs (2007)
EN
OB
Analog input frequency, Hz
1 ps (1999)
Photon
ic
ADCs
104 105 106 107 108 109 1010 101102468
101214161820
this
0.1 fs
work
1 fs10 fs
100 fs (2007)
EN
OB
Analog input frequency, Hz
1 ps (1999)
Photon
ic
ADCs
Voltage!
t!T!o!
Δt!V!o!ΔV!
75!G. C. Valley, Opt. Express 15, 1955 (2007) R. H. Walden, ADC in the early 21st century, IMS 2007.
„Walden Plot“
State of the Art Electronic ADC and Beyond
Nortel Inc.: 40 GSa/s CMOS Y. M. Greshishchev, et al. ISSCC, paper 21.7 (2010). Fujitsu Inc.: 65 GSa/s CMOS http://www.fujitsu.com RPI: 40 GSa/s SiGe ADC M. Chu, et al. IEEE J. Solid State Circuits 45, 380 (2010).
Wavelength Multiplexed Optical Sampling
76!
! Effective sampling rate = laser rep rate (1/T) x number of multiplexed channels (N)
! Sampling jitter is set by MLL timing jitter ! Digitization is performed in electronic domain ! Down counting by WDM
Eliminate aperture jitter, demultiplex to lower rate channels T. Clark, Time and wavelength interleaved phot. Sampler , PTL 99.
Integrated Silicon Photonic ADC
77!
Modulator input Photodetector outputs (8 total)
Ring and bias heater controls
ADC chip (7×3.25
mm) input coupler
12 microring heater contact pads
metal layer
8 photodetector contact pads
MZ modulator with RF and bias heater pads
photodetectors
ring filters with heaters
1 mm
silicon structures
ch1
ch2
ch3
ch1
ch2
ch3
ch2, bottom
ch3, bottom
through, bottom
through, top
ch3, top
ch2, top
ch1, top
ch1, bottom
Si metal
Grein et al., CLEO 2011, paper CThI1 Khilo et al., Opt. Exp. (20) 4454 (2012)
Acknowledgement!Students: M. Peng (JPL) and P. Callahan, K. Safak, A. Kalaydzyan J. Kim (Prof. KAIST); A. Benedick and C. Sorace-Agaskar (MIT Lincoln Laboratory) A. Khilo and M. Dahlem (both Prof. MASDAR Institute of Technology) J. Cox (Sandia National Laboratory), M. Sander (Prof. Boston University) A. Motamedi (INTEL) Postdocs: M. Xi, Q. Zhang, T. Schibli and M. Popovic (both Prof. University of Colorado, Boulder) F. O. Ilday (Prof. Bilkent University) Research Scientists: O.D. Mücke, N. Chang, A. Nejadmalayeri (Samsung) Collaborators: Holger Schlarb and Ingmar Hartl (DESY) E. Ippen, F. Wong, M. Watts, R. Ram, J. Orcutt (MIT) E. Monberg, M. Yan, L. Grüner-Nielsen, J. Fini (OFS) S. Spector, T. Lyscczarz, M. Geis, M. Grein, J. Wang, J. Yoon (MIT – Lincoln Lab.)
78!