1. Lasers and RF-Timing Franz X. Kaertner
Department of Electrical Engineering and Computer Science and
Research Laboratory of Electronics,
Massachusetts Institute of Technology, Cambridge, USA
First I like to thank the organizers for inviting me to give a seminar talk on our work on short pulse generation. Approaching the single-cycle regime. This works was suppoerted by

2. Outline I. System Overview II. Timing Distribution
III. RF-Synchronization
IV. Some Experimental Results
V. Photo-Injector
VI. Long Seed Pulse Generation
VII. Conclusion

3. Facility concept W.S. Graves, MIT Bates Laboratory Master oscillator
Fiber link synchronization
UV Hall
X-ray Hall
Seed laser
Pump laser
Seed laser
Pump laser
Undulators
100 nm
Undulators
30 nm
1 nm
Injector laser
10 nm
0.3 nm
SC Linac
0.3 nm
SC Linac
0.1 nm
1 GeV
2 GeV
4 GeV
10 nm
Future upgrade to 0.1 nm at 8 GeV
3 nm
1 nm
Undulators
Seed laser
Pump laser
Nanometer Hall
W.S. Graves, MIT Bates Laboratory

4. Timing Distribution Optical Master Oscillator Mode-locked Laser
RF-Clock
100 MHz
Timing Stabilized Fiber Links
HHG-Seed
Dt = 10 fs
Probe Laser
Dt = 10 fs
Photo-Inj.
Dt = 100 fs
SC-Accel.
1.3 GHz
Dt=200 fs
Linearizer
3.9 GHz
Dt=10 fs
RF-Switch
0.65 GHz
Dt=200 fs
10kHz
5ms
Pulsed
Klystron
Undu-
lator
Gun
Linac
Dt: Required Timing Jitter in Each Section
10 fs ~ 3mm

5. Timing Stabilized Fiber Links (<1km)
PZT
Cross
Correlator
Fiber
Fixed Length L
ML - Laser
Assuming no fiber length fluctuations faster than 2L/c.

6. Cooperation on Frequency Metrology and Timing Distribution
Both at MIT and JILA-NIST: MURI-Projects funded by ONR
Frequency Metrology
and
Femtosecond Technology for Optical Clocks
MIT:
E. P. Ippen (PI)
Y. Fink
F. Kaertner
D. Kleppner
L. Kolodziejski
J. Shapiro
F. Wong
JILA-NIST:
J. Ye (PI)
S. Diddams
L. Holberg
…..
J. Ye, JOSA B 20, 1459 – 1469 (2003)

7. Experimental Results on Transmission of Optical Frequency Standards
By active fiber induced phase noise cancelation

8. Sub-10 fs RF-Synchronization
(Mike Perrott, MTL, MIT-Proprietary Information)
Repetition
Rate: fR l 4
PBS
Phase
Modulator
RF: f = m fR
Recovered from optical pulse train
VCO
Loop
Filter

9. Experimental Results on Synchronization
Synchronization of a 5fs Ti:Sapphire 800 nm
and a 30 fs Cr:Forsterite 1300 nm
with 0.3 fs timing jitter measured
from 1mHz to 2.3 MHz.

10. 5fs Ti:sapphire Laser 1mm BaF2 f = 10o OC 1 PUMP OC 2 BaF2 - wedges
Laser crystal:
2mm Ti:Al2O3
f = 10o
OC 1
PUMP
L = 20 cm
OC 2
BaF2 - wedges
Base Length = 30cm for 82 MHz Laser

11. Laser Spectra
Ti:sapphire
Cr:forsterite
5 fs fs

12. Balanced Cross-Correlator
Output
( nm) Δt
Ti:sa
Cr:fo
3mm
Fused Silica
SFG
Rep.-Rate
Control
(1/496nm = 1/833nm+1/1225nm). 0V

13. Balanced Cross-Correlator
Output
( nm) Δt 0V - Δt Δt
Ti:sa
Cr:fo
3mm
Fused Silica
SFG
Rep.-Rate
Control
(1/496nm = 1/833nm+1/1225nm). 0V + GD
-GD/2 + -

14. Balanced Cross-Correlator

15. Measuring the residual timing jitter
Output
( nm)
Jitter
Analysis
SFG
Ti:sa
Cr:fo
3mm
Fused Silica
Rep.-Rate
Control
(1/496nm = 1/833nm+1/1225nm). GD
-GD/2

16. Experimental result: Residual timing-jitter
The residual out-of-loop timing-jitter measured from 10mHz to 2.3 MHz is 0.3 fs (a tenth of an optical cycle)
Long Term Drift Free

18. 1 Laser System & Synchronization
Fiberlink + Synchronization
Photo-Injector:
10-20 ps Pulses
1-10 mJ
1-10 kHz
@ 266 nm
(conv. NLO)
High Harmonic
Generation
> 10 nJ
Sub fs – 10 fs, 2ps
1-10 kHz
@ 8,30,200 nm
X00 m
10 fs
Timing Jitter
E-beam
LINAC
FEL

19. Directly Diode-pumped Photo-Injector
To achieve a homogeneous e-beam bunch
Temporal: Flat-top shaped
Yb:fiber amplifier
IPG-Photonics
20ps, 10mJ, 1-10 kHz
@ 1064 nm
4th-Harmonic
20ps, 1mJ, 1-10 kHz
@266 nm
Acusto-Optic
Programable
Pulse Shaper
(Dazzler,
Fastlight)
Yb:YAG,
1ps
rep. Rate
100 MHz
Pulse
Selector

20. Long Pulse Seed Generation
2ps, 200 (266) nm
Yb: YAG
CPA
2ps, 20mJ, 1-10 kHz
@1064 nm
4th-Harmonic
2ps, 1mJ, 1-10 kHz
@ 200 (266) nm
Acusto-Optic
Programable
Pulse Shaper
(Dazzler,
Fastlight)
Yb:YAG,
2ps
rep. Rate
100 MHz
Pulse
Selector

21. Conclusions
Seeding needs 10 fs timing distribution over 300m distances (rel. precision 10-8). Can be accomplished by length stabilized fiber links.
Fiber noise eliminated by active feedback.
Scheme for phase stable RF-regeneration has been outlined
Less than 0.3 fs between independent lasers has been demonstrated,  Optical Clock distribution.
Photo-Injection Laser: Mode-locked Yb:YAG laser and amplifier
Long wavelength seed: Mode-locked Yb:YAG laser and CPA