1. MIT Optics & Quantum Electronics Group Seeding with High Harmonics Franz X. Kaertner Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, USA

2. MIT Optics & Quantum Electronics Group Outline I. Advantages of Seeding II. High-Harmonic Generation III. Optimization of High-Harmonic Generation IV. Carrier-Envelope Phase Control V. Conclusion

3. MIT Optics & Quantum Electronics Group SASE properties GINGER simulation of SASE FEL at 0.3 nm. Time profileTime profile (log plot)Spectrum Electron beam parameters Energy4.0 GeV Peak current (amp)2000 A RMS emittance 0.8  m RMS energy spread.01 % Charge80 pC Beam power8.0 TW Bunch FWHM40 fs Laser beam parameters Pulse FWHM35 fs (~ebeam length) Saturation power~3.0 GW Energy0.2 mJ FWHM linewidth7.0E-4 Saturation length59 m For simulation speed. True bunch length will be longer. W.S. Graves, MIT Bates Laboratory

4. MIT Optics & Quantum Electronics Group Seeding for narrow linewidth Output time profileTime profile (log plot) Spectrum Seed laser parameters FWHM50 fs Power0.1 MW Pulse energy 5 nJ FEL output parameters Saturation FWHM 30 fs Saturation power~2.0 GW Saturation energy 0.1 mJ FWHM linewidth 1.0E-5 Saturation length28 m GINGER simulation of seeded FEL at 0.3 nm. Same ebeam parameters as SASE case. W.S. Graves, MIT Bates Laboratory

5. MIT Optics & Quantum Electronics Group Seeding for short pulse Output time profileTime profile (log plot)Spectrum Seed laser parameters FWHM0.5 fs Power10.0 MW Pulse energy 5 nJ FEL output parameters Saturation FWHM 0.75 fs Saturation power~2.0 GW Saturation energy 1.5  J FWHM linewidth 6.0E-4 Undulator length20 m GINGER simulation of seeded FEL at 0.3 nm. Same ebeam parameters as SASE case. W.S. Graves, MIT Bates Laboratory

6. MIT Optics & Quantum Electronics Group High-Harmonic Generation Noble Gas Jet (He, Ne, Ar, Kr) 100  J - 1 mJ @ 800 nm XUV @ 3 – 30 nm  = 10 -8 - 10 -5 Recombination Propagation -W b  XUV Energy  x bb 0 Laser electric field Ionization Cut-off Harmonic:

7. MIT Optics & Quantum Electronics Group Sub-fs High-Harmonic Generation M. Hentschel, et al., Nature, 414, 509 (2001) A. Baltuska, et al., Nature, 421, 612 (2003) Highest wavelength emitted depends on carrier-envelope phase Single-Attosecond pulse (650 as) -> Stable seed energy is only possible with phase controlled laser source Time Electric Field  = 0  =  /2

8. MIT Optics & Quantum Electronics Group Dependence of HHG on carrier-envelope phase Atomic dipole moment depends on electric field HHG depends on carrier-envelope phase, particularly near cutoff Experiment: Laser intensity.7x10 15 W/cm 2, pulsewidth 5 fs, propagation of 2mm neon, for various carrier-envelope phases Clear dependence of HHG near the cutoff harmonic on CEP Discussion with H. C. Kapteyn: Also 20 fs driver pulses need carrier-envelope stababilization Ref. Brabec et al. … A. Baltuska, et al., Nature, 421, 612 (2003)

9. MIT Optics & Quantum Electronics Group Published Results: Early pioneers: McPherson et al., J. Opt. Soc Am B4, 595 (1987) Ferry et al., J. Phys. B 21, 131 (1987) New results: Takahashi et al.: 16 mJ, 35 fs, @800nm 300 nJ @ ~30nm), Postdeadline Paper CLEO 2002 Schnürer et al.: Few-cycle pulse: 1mJ, 5 fs  =10 -6, 1 nJ@ ~30nm Phys. Rev. Lett. 83, 722-725 (1999) Bartels et al.: Shaped pulses: Nature 406, 164 (2000) improvement by a factor of 10 @ 30 th harmonic H. C. Kapteyn  =10 -4 - 10 -5 @ 30 th harmonic Quasi-Phase-Matching: Nature 421, 51 (2002) improvement by a factor of 7 @ 30 th harmonic -> 1 0 nJ improvement by a factor of 100 @ 100 th harmonic

10. MIT Optics & Quantum Electronics Group High Harmonic Generation in Hollow Fibers Courtesy of M. Murnane and H. Kapteyn, JILA

11. MIT Optics & Quantum Electronics Group Pulse shaping of drive laser can enhance a single harmonic Courtesy of M. Murnane and H. Kapteyn, JILA Quasi-phase matching in modulated hollow-core waveguide. Optimization of HHG How much improvement can we get with additional phase control for the very high harmonics in the water window < 4 nm ?

12. MIT Optics & Quantum Electronics Group HHG spectra for 3 different periodicities of modulated waveguides. Courtesy of M. Murnane and H. Kapteyn, JILA HHG has produced wavelengths from 50 nm to few nanometers, but power is very low for wavelengths shorter than ~10 nm. Best power at 30 nm. Improvements likely to yield 10 nJ at 8 nm. Rapidly developing technology.

13. MIT Optics & Quantum Electronics Group Few-Cycle Pulse and HHG Generation In Photonic Bandgap Fiber (Y. Fink, RLE@MIT) Truly guided modes (assuming infinite coating thickness, strong differentiation between different modes, large core fibers effectively in single mode Modal Dispersion can be engineered for optimum pulse compression and/or phase and group velocity matching in HHG. Temelkuran et al., Wavelength-scalable hollow optical fibers with large photonic bandgaps …, Nature, 2002. 420: p. 1885-1886. Chalcogenide Glass Poly-Ether Sulfone (PES)

14. MIT Optics & Quantum Electronics Group Modification of Dispersion in PBG-Fibers Matching of group and phase velocities is possible

15. MIT Optics & Quantum Electronics Group Phase Controlled Laser Pulses Carrier-Envelope Phase  CE Envelope Field Maximum field depends on  CE L. Xu, et al., Opt. Lett. 21, 2008, (1996) Electric field of a 1.5-cycle optical pulse

16. MIT Optics & Quantum Electronics Group Carrier-Envelope Phase and Frequency Metrology Periodic Pulse Train with T R = 1 ff T. Udem, et al., PRL 82, 3568 (1999) D. Jones, et al., Science 288, 635-639 (2000) SHG Frequency f o ff f o + ff f o -... 0 f CEO Spectrum Optical Clocks Provides an ultrastable modelocked pulse train! The clock of the Facility

17. MIT Optics & Quantum Electronics Group Octave, Prismless Ti:sapphire Laser Laser crystal: 2mm Ti:Al 2 O 3   PUMP OC 1 OC 2 Base Length = 30cm for 82 MHz Laser L = 20 cm BaF2 - wedges 1mm BaF2

18. MIT Optics & Quantum Electronics Group DCM-Pairs Covering One Octave Pump Window

19. MIT Optics & Quantum Electronics Group Spectra from 80 MHz and 150 MHz Laser

20. MIT Optics & Quantum Electronics Group Broadband, Prismless Ti:sapphire Laser and Carrier-Envelope Detection

21. MIT Optics & Quantum Electronics Group Carrier-Envelope Beat Frequency Comb for Optical Metrology on Ultracold Hydrogen by Prof. Kleppner

22. MIT Optics & Quantum Electronics Group High-Harmonic Seed Generation (CPA) A. Baltuska, et al., Nature, 421, 611 (2003) 0.5 mJ

23. MIT Optics & Quantum Electronics Group High-Harmonic Seed Generation (P-CPA) Yb:YAG Amplifier 1ns, 20mJ, 1-10 kHz @1064 nm Q-switched Yb:YAG, 1ns, 1  J 1-10 kHz 2 nd -Harmonic 1ns, 10mJ, 1-10 kHz @ 532 nm Carrier-Envelope Stabilized Ti:Sapphire, 4 fs, 100MHz GV-matched P-CPA with BBO 5fs, 5mJ 1-10 kHz Stret- cher Com- pressor Phase Control

24. MIT Optics & Quantum Electronics Group Stable HHG needs phase controlled high energy pulses (It has been shown to be possible) Optimization of HHG results already to 10 -5 efficiency at 30 nm -> 10 nJ seed energies. Photonic Band Gap fibers lead to novel opportunities for HHG generation because of novel opportunities for phase and group velocity matching Laser technology is rapidly developing from CPA  P-CPA Conclusions