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
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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
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.)