Extreme ultraviolet radiation with coherence time greater than 1 s

Many atomic and molecular systems of fundamental interest possess resonance frequencies in the extreme ultraviolet (XUV) where laser technology is limited and radiation sources have traditionally lacked long-term phase coherence. Recent breakthroughs in XUV frequency comb technology have demonstrated spectroscopy with unprecedented resolution at the megahertz level, but even higher resolutions are desired for future applications in precision measurement. By characterizing heterodyne beats between two XUV comb sources, we demonstrate the capability for sub-hertz spectral resolution. This corresponds to coherence times >1 s at photon energies up to 20 eV, more than six orders of magnitude longer than previously reported. This work establishes the ability of creating highly phase-stable radiation in the XUV with performance rivalling that of visible light. Furthermore, by direct sampling of the phase of the XUV light originating from high-harmonic generation, we demonstrate precise measurements of attosecond strong-field physics.

[1]  S. R. Huisman,et al.  Inhibited spontaneous emission of quantum dots observed in a 3D photonic band gap. , 2011, Physical review letters.

[2]  Joseph Nordgren,et al.  Novel instruments for ultra-soft X-ray emission spectroscopy , 2009 .

[3]  H. G. Muller,et al.  Attosecond Synchronization of High-Harmonic Soft X-rays , 2003, Science.

[4]  E. Eyler,et al.  Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy , 2007, 0704.3430.

[5]  Jun Ye,et al.  Output coupling methods for cavity-based high-harmonic generation. , 2006, Optics express.

[6]  Temporal Coherence of Ultrashort High-Order Harmonic Pulses , 1998 .

[7]  T. Eidam,et al.  Megawatt-scale average-power ultrashort pulses in an enhancement cavity. , 2014, Optics letters.

[8]  Ingmar Hartl,et al.  80 W, 120 fs Yb-fiber frequency comb. , 2010, Optics letters.

[9]  Kenneth J. Schafer,et al.  Semiclassical approaches to below-threshold harmonics , 2010 .

[10]  Lei Chen,et al.  A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity , 2011, Nature Photonics.

[11]  Hogervorst,et al.  xuv-laser spectroscopy of HD at 92-98 nm. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[12]  Jane Lee,et al.  Intracavity ionization and pulse formation in femtosecond enhancement cavities. , 2011, Optics letters.

[13]  Marco Bellini,et al.  Direct interferometric measurement of the atomic dipole phase in high-order harmonic generation. , 2006, Physical review letters.

[14]  R. Holzwarth,et al.  Femtosecond optical frequency combs , 2009 .

[15]  F. Krausz.  Attosecond Physics , 2007, 2007 Conference on Lasers and Electro-Optics - Pacific Rim.

[16]  R. Jones,et al.  Optimizing intracavity high harmonic generation for XUV fs frequency combs. , 2011, Optics express.

[17]  V. Dzuba,et al.  Single-ion nuclear clock for metrology at the 19th decimal place. , 2011, Physical review letters.

[18]  Jun Ye,et al.  Optical frequency comb with submillihertz linewidth and more than 10 W average power , 2008 .

[19]  Zenghu Chang,et al.  Fundamentals of Attosecond Optics , 2011 .

[20]  Fritz Keilmann,et al.  Time-domain mid-infrared frequency-comb spectrometer. , 2004, Optics letters.

[21]  M. Zhu,et al.  An introduction to phase-stable optical sources , 1993 .

[22]  Y. Mairesse,et al.  Resolving the time when an electron exits a tunnelling barrier , 2012, Nature.

[23]  A. Mills,et al.  XUV frequency combs via femtosecond enhancement cavities , 2012, 1206.0408.

[24]  Theodor W. Hänsch,et al.  Feasibility of Coherent xuv Spectroscopy on the 1S-2S Transition in Singly Ionized Helium , 2009 .

[25]  Motoichi Ohtsu,et al.  Frequency control of semiconductor lasers , 1993 .

[26]  J. Ye,et al.  Extreme nonlinear optics in a femtosecond enhancement cavity. , 2011, Physical review letters.

[27]  Jun Ye,et al.  Vacuum-ultraviolet frequency combs from below-threshold harmonics , 2009, 0901.3768.

[28]  S. Suckewer,et al.  Soft x-ray lasers and their applications. , 1990, Science.

[29]  Wei Zhang,et al.  An optical lattice clock with accuracy and stability at the 10−18 level , 2013, Nature.

[30]  J. Ye,et al.  Femtosecond Optical Frequency Comb: Principle, Operation and Applications , 2010 .

[31]  K. Eikema,et al.  Extreme ultraviolet frequency comb metrology. , 2010, Physical review letters.

[32]  U. Keller,et al.  Quantum-path interferences in high order harmonic generation , 2007, 2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference.

[33]  Jun Ye,et al.  Femtosecond pulse amplification by coherent addition in a passive optical cavity. , 2002, Optics letters.

[34]  A. Ruehl,et al.  Power optimization of XUV frequency combs for spectroscopy applications [Invited]. , 2011, Optics express.

[35]  D. Attwood.  Soft X-Rays and Extreme Ultraviolet Radiation , 1999 .

[36]  J. Larruquert,et al.  Electron-beam deposited boron coatings for the extreme ultraviolet. , 2008, Applied optics.

[37]  Jun Ye,et al.  Direct frequency comb spectroscopy in the extreme ultraviolet , 2011, Nature.

[38]  Thomas Udem,et al.  A frequency comb in the extreme ultraviolet , 2005, Nature.

[39]  Jun Ye,et al.  Phase-coherent frequency combs in the vacuum ultraviolet via high-harmonic generation inside a femtosecond enhancement cavity. , 2005, Physical review letters.

[40]  Ryszard S. Romaniuk,et al.  Operation of a free-electron laser from the extreme ultraviolet to the water window , 2007 .

[41]  Jun Ye,et al.  Optical spectrum analyzer with quantum-limited noise floor. , 2013, Physical review letters.

[42]  G. Aeppli,et al.  Proceedings of the International School of Physics Enrico Fermi , 1994 .

[43]  Fred L. Walls,et al.  RF Spectrum of a Signal after Frequency Multiplication; Measurement and Comparison with a Simple Calculation , 1975, IEEE Transactions on Instrumentation and Measurement.

[44]  L'Huillier,et al.  Phase of the atomic polarization in high-order harmonic generation. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[45]  T. Hänsch,et al.  Optical frequency metrology , 2002, Nature.

[46]  V. Dzuba,et al.  Electron-hole transitions in multiply charged ions for precision laser spectroscopy and searching for variations in α. , 2011, Physical review letters.

[47]  J. Levesque,et al.  Tomographic imaging of molecular orbitals , 2004, Nature.

[48]  P. Villoresi,et al.  Measurement of harmonic phase differences by interference of attosecond light pulses. , 2005, Physical review letters.

[49]  S. T. Pratt,et al.  Femtosecond electronic response of atoms to ultra-intense X-rays , 2010, Nature.

[50]  K. Eikema,et al.  Ramsey-comb spectroscopy with intense ultrashort laser pulses , 2013, Nature Physics.

[51]  Jun Ye,et al.  Efficient output coupling of intracavity high-harmonic generation. , 2008, Optics letters.

[52]  Tino Eidam,et al.  Compact high-repetition-rate source of coherent 100 eV radiation , 2013, Nature Photonics.

[53]  Jun Ye,et al.  Colloquium: Femtosecond optical frequency combs , 2003 .

[54]  D. Ratner,et al.  First lasing and operation of an ångstrom-wavelength free-electron laser , 2010 .