1. High-resolution spectroscopy with a femtosecond laser frequency comb Vladislav Gerginov 1, Scott Diddams 2, Albrecht Bartels 2, Carol E. Tanner 1 and Leo Hollberg 2 1 Department of physics, University of Notre Dame, Notre Dame, IN 46556 2 National Institute of Standards and Technology, 325 Broadway M.S. 847, Boulder, CO 80305

2. Atomic number: 55 Atomic weight: 132.9 a.u. El. Configuration: [Xe] 6s 1 Nuclear angular momentum 7/2 T melt. = 28.4 o C T evap. = 669 o C Lifetime 6P 3/2 = 30.462(3) ns (1) Lifetime 6P 1/2 = 34.88(2) ns (1) Nucl. dipole moment:  I = 2.5827681(14)  N (2) Nucl. quadrupole moment: Q = - 3.431(1) mbarn (3) HFS 6S 1/2 (4) HFS 6P 1/2 (preliminary) HFS 6P 3/2 (5) 1 C.Amiot et al., Phys. Rev. A66, 052506 (2002) 2 P. Raghavan, At. Data Nucl. Data Tables, 42, 189 (1989) 3 J. Cederberg et al., J.Chem. Phys. 111 (18), 8396 (1999) 4 International Agreement 5 V. Gerginov et al., Phys. Rev. Lett. 91,072501 (2003)

3. Pulsed laser spectroscopy 1970s: Ideas of 2-photon spectroscopy with pulsed sources from T. W. Hänsch and V. P. Chebotaev; “Narrow resonances of two-photon absorption of super-narrow pulses in a gas” Y. V. Baklanov and V. P. Chebotaev, Appl. Phys. 12, 97 (1977). “Coherent Two-Photon Excitation by Multiple Light Pulses” R. Teets, J. Eckstein, and T. W. Hänsch Phys. Rev. Lett. 38, 760-764 (1977). “Two-photon spectroscopy of laser-cooled Rb using a mode-locked laser”, M. J. Snadden, A. S. Bell, E. Riis, A. I. Ferguson, Opt. Commun, 125, 70-76, (1996). “High sensitivity phase spectroscopy with picosecond resolution” J. –C. Diels, B. Atherton, S. Diddams; Proceedings of 5th European Quantum Electronics Conference, 29 195–195, (1994). “United Time-Frequency Spectroscopy for Dynamics and Global Structure”, A. Marian, M. C. Stowe, J. R. Lawall, D. Felinto, J. Ye, Science Express, 1105660, 2004.

4. Experimental setup

5. Femtosecond Laser Spectral Output

6. D 1 line spectrum @ 14nW CW power

7. D 2 line spectrum –CW excitation

8. D 2 line spectrum @ 1.5nW CW power

9. Overlapped spectral components

10. D 1 Line Measurements F-F’Previous 1 (kHz)This work (kHz)Difference (kHz)AC Stark shift (kHz) F3-F3335120562759.7(4.9)335120562753.7(85.0)-6.0 ( 0.1 sigma)Not meas. F3-F4335121730483.2(5.3)335121730500.8(16.4)17.6 (1 sigma)-36.0(31.4) F4-F3335111370130.2(4.6)335111370146.3(10.5)16.1 (1.4 sigma)-20.7(9.5) F4-F4335112537853.9(4.0)335112537861.7(28.0)7.8 ( 0.3 sigma)Not meas. 1 V. Gerginov, K. Calkins, C. E. Tanner, A. Bartels, J. McFerran, S. Diddams, L. Hollberg, to be submitted.

11. F-F’Previous 1 (kHz)This work (kHz)Difference (kHz) F3-F2351730549621.5(5.5)351730549616.3(9.7)-5.2 (0.5 sigma) F3-F3351730700845.9(5.5)351730700766.1(98.5)-79.8(0.8 sigma) F3-F4351730902133.2(5.6)351730902116.9(34.2)-16.3 (0.5 sigma) F4-F3351721508210.5(5.5)351721508195.1(21.7)-15.4 (0.7 sigma) F4-F4351721709496.9(5.5)351721709471.6(167.8)-25.3( 0.2 sigma) F4-F5351721960585.7(5.5)351721960563.5(4.5)-22.2( 3 sigma) D 2 Line Measurements 1 V. Gerginov, C. E. Tanner, S. Diddams, A. Bartels, L. Hollberg, PRA 70, 042505, 2004

12. Cs D 2 Line Optical Clock

13. Frequency reference Combining the optical frequencies of the D lines, the repetition rate and the offset frequency of the femtosecond laser can be referenced to an atomic transition.

14. Optical frequency 351730549621500Hz Repetition rate 998.6390777MHz Component number N=352210 Accuracy 60kHz (1.7x10 -10 ) Instability 3.5kHz (10 -11 ) @ 100s

15. Conclusions 1.One-photon spectroscopy using the output of a femtosecond laser; 2.Optical frequency measurements with accuracy better than 100kHz; 3.SubDoppler spectroscopy with 1nW laser power; 4.Potential femtosecond-laser based optical clocks.