Embed Size (px)
Citation preview
UCLA WorkshopMay 19th, 2009
Large Scale Femtosecond Timing Distribution for X-ray Free Electron Lasersfor X-ray Free Electron Lasers
Franz X Kärtner Jungwon Kim Jonathan Cox Jeff ChenFranz X. Kärtner, Jungwon Kim, Jonathan Cox, Jeff Chen, William Graves and David Moncton
Department of Electrical Engineering and Computer ScienceDepartment of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology
Cambridge MA USA
Cambridge, MA, USA
OutlineSynchronization System Layout for Seeded FEL
Ad t f P l d O ti l Di t ib ti S tAdvantages of a Pulsed Optical Distribution System
Low Noise Optical Master Oscillators
Timing Distribution Over Stabilized Fiber Links
Optical-to-Optical Synchronization
RF-Extraction and Locking to Microwave References
Long Term Stable Sub-10 fs System Performance
2
Long Term Stable Sub-10 fs System Performance
Seeded X-ray Free Electron Laser
Long-term sub-10 fs synchronization over entire facility is required.
3
Seeded X-ray Free Electron Laser
4
J. Kim et al, FEL 2004.
Why Optical Pulses (Mode-locked Lasers)?TR = 1/fRTR 1/fR
frequency
… ...
fR 2.fR N.fRtime
Real marker in time and RF domain, every harmonic can be extracted at the end station
frequencytime
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 lasersoptical synchronization of other lasers.Pulses can be directly used to seed amplifiers, EO-sampling, ….Group delay is directly stabilized, not optical phase delay.
5
After power failure system can auto-calibrate.
200 MHz Soliton Er-fiber Laser
ISO λ/4λ/4
lli t
10 cmSMF
10 cmSMF
ISO λ/4λ/4
lli t
10 cmSMF
10 cmSMF
PBS λ/2 collimatorcollimator
M980 nm Pump
PBS λ/2 collimatorcollimator
M980 nm Pump
WDMPump
50 cmEr doped fiber 10 cm
SMF
10 cmSMF
WDMPump
50 cmEr doped fiber 10 cm
SMF
10 cmSMF
• 200 MHz fundamentally modelocked soliton fiber laser
SMFSMF
J. Chen et al, Opt. Lett. 32, 1566 (2007).K. Tamura et al. Opt. Lett. 18, 1080 (1993).
• 167 fs pulses
• 40mW output power
, p , ( )
6
Similar lasers are now commercially available!
200 MHz, 100fs MenloSystems GmbH Laser
7
200 MHz soliton laser: J. Chen et al., Opt. Lett. 32, 1566 (2007)
Sensitive Time Delay Measurements by
Balanced Optical Cross CorrelationBalanced Optical Cross Correlation
8
Single-Crystal Balanced Cross-Correlator
T II h t h dType-II phase-matchedPPKTP crystal
Reflect fundamentalT it SHGTransmit fundamental Transmit SHGTransmit fundamental
Reflect SHG
9
J. Kim et al., Opt. Lett. 32, 1044 (2007)
Single-Crystal Balanced Cross-Correlator
In comparison:Typical microwave mixer
80 pJ, 200 fs 1550nm input pulses
10
Typical microwave mixerSlope ~1 μV/fs @ 10GHz
p pat 200 MHz rep. rate
Sub-fs Timing Jitter Performance
11
Ultralow timing jitter (<1 fs) in the high frequency range [100 kHz, 10 MHz]
Timing - StabilizedFiber Links
12
Timing-Stabilized Fiber Links
PZT-based fiberFiber link ~ several hundreds metersPZT based fiber
stretcher
Mode-locked laser
to a few kilometers
isolator
TimingComparison
Faradayrotatingmirror
Cancel fiber length fluctuations slower than the pulse travel time (2nL/c)
1 km fiber: travel time = 10 μs ~100 kHz BW
13
1 km fiber: travel time = 10 μs ~100 kHz BW
2 Link Test System
J. Cox et al. CLEO 2008.
Experimental Apparatus300 ti l fib~300 m optical fiber
Piezo stretcher
200 MHz Laser EDFA
In-LoopPPKTP Out-of-Loop
PPKTP
Invar BoardBoard
Motor
Balanced Cross-Correlation Signals
2000
Link 1 In Loop S-Curve, slope = 21 mV/fs
V)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
-2000
0
2000
Sign
al (m
V
time (ms)
Link 1
time (ms)
2000
0
2000
Link 2 In Loop S-Curve, slope = 18 mV/fs
gnal
(mV)
Link 2
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
-2000Sig
time (ms)
2000
Out of Loop S-Curve, slope = 20 mV/fs
V)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
-2000
0
Sign
al (m
V
time (ms)
Out ofLoop
time (ms)
4000
6000
8000100 Hz PZT Modulation
se S
hift
(fs)
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
2000
Phas
time (ms)
Results – Timing Jitter
104
/Hz)
2 5
3
s)
100
102
Den
sity
(fs2 /
2
2.5
Jitte
r (fs
rms
10-4
10-2
ter S
pect
ral
1
1.5
Inte
grat
ed J
10-4
10-3
10-2
10-1
100
101
102
103
104
105
10-6Ji
tt
10-4
10-3
10-2
10-1
100
101
102
103
104
1050
0.5
360 as (rms) timing jitter from 1 Hz to 100 kHz3 3 f ( ) i i ji f 3 H 100 kH
Frequency (Hz)
3.3 fs (rms) timing jitter from 35 μHz to 100 kHz
O i l O i l S h i iOptical-to-Optical Synchronization
18
Optical-to-Optical Synchronization
19
Ti:sapphire Laser + Cr:Forsterite Laser
Spanning over 1.5 octaves
Ti:sapphire Cr:forsterite
5fs 30 fs
20
Sub-femtosecond Residual Timing JitterBalanced optical cross correlator based on GDD (T Schibli et al OL 28 947 (2003))Balanced optical cross-correlator based on GDD (T. Schibli et al, OL 28, 947 (2003))
Long-term drift-free sub-fs timing synchronization over 12 hours
21
J. Kim et al, EPAC 2006.
Long-term drift-free sub-fs timing synchronization over 12 hours
Optical to RF ConversionOptical-to-RF Conversion or
Optical-to-RF Lockingfnecessary for
Locking OMO to RMOg
22
Direct Extraction of RF from Pulse Train
AM to PM conversion
E. Ivanov et al, IEEE UFFC 52, 1068 (2005). IEEE UFFC 54, 736 (2007).
AM-to-PM conversion,Temperature driftof photodetectors and mixers
TR/n…
TR = 1/fR t
… ...
t
RF frequency
… ...
fR 2fR nfRtime Photodetector
23
RF frequencyPhotodetector
Direct Extraction of RF from Pulse Train
55 fs driftin 100 sec
T /
T 1/f
TR/n
A. Bartels et al, OL 30, 667 (2005).TR = 1/fR t
( )
… ...
fR 2fR nfRtime
24
RF frequencytime Photodetector
More in: B. Lorbeer et al, PAC 2007.
Balanced Optical-Microwave Phase Detector(BOM-PD)
Microwave
(BOM PD)
Signal
Electro-optic sampling of microwave signal with optical pulse train
25
J. Kim et al., Opt. Lett. 31, 3659 (2006).
Electro-optic sampling of microwave signal with optical pulse train
Optoelectronic Phase-Locked Loop (PLL)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) RegeneratedDetector (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
26
Testing Stability of BOM-PDs
BOM-PD 1: timing synchronizationBOM-PD 2: out-of-loop timing characterization
27
BOM PD 2: out of loop timing characterization
Long-Term Stability: 6.8 fs drift over 10 hours
RMS timing jitter integrated in 27 μHz – 1 MHz: 6.8 fs
28
J. Kim et al, Nature Photonics 2, 733 (2008).
ConclusionsLong term stable (10h) sub-10 fs timing distribution systemLong term stable (10h) sub 10 fs timing distribution system is completed.
True long term stability (forever): Polarization Control (in progress)
Master Oscillators commercially available + amplifier >400mW of
10 li k )
SBR1cm
output power > 10 links)
500 MHz, 400 fs Cyoptics
300 m Fiber Links, over 10h < 5 fs ( < 1fs possible)
Optical-to-Optical Synchronization, over 12h < 1fsOptical to Optical Synchronization, over 12h < 1fs
Optical-to- Microwave Synch., over 10h < 7fs ( < 1fs possible)
C i li ti b M l t I d G bH
29
Commercialization by Menlosystems Inc. and GmbH
