1. 1 Frekvenčni standard in merjenje z optičnim glavnikom

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3. 3 Nobel prize 2005 Nobel Prize in Physics was awarded to Roy J. Glauber, John L. Hall and Theodor W. Hänsch in 2005. The last two have made pioneering contributions to the development of the optical frequency comb technique.

4. 4 Exciting time for light control Continuous wave laser: < 1 Hz stability and accuracy Ultrafast pulse: < 1 fs generation and control

5. 5 Recipe for a Wavelength Standard Atomic or molecular absorption lines - Absolute frequency reference. - Very stable under changing environmental conditions

6. 6 Frequency Measurement Frequency = Cycles/second Definition of time Caesium 133 atom Optical frequency ----- In hundreds of THz Its easy to measure in THz ? Photo Detector ------ In 40-100 GHz What we need to do? Mode LockingFrequency Comb Duration of 9 192 631 770 period Of the radiation corresponding to the transition between two hyperfine Level of the ground state of Cs atom.

7. 7 Merjenje optične frekvence

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9. 9 Basics Optična ura povezuje mikrovalovne in optične frekvence  0  cosine-pulsesine-pulse - cosine-pulse  /2 I()I() 1 cc E(t)=A(t)e i  c t = ++ m=-m=-  A m e -im  r t-i  c t

10. 10 Frekvenčni offset

11. 11 Time-Frequency Correspondence   r  t = 1/f r t E(t)E(t)  0 f n = n f r + f o I(f)I(f) f frfr fofo f r Laser repetition rate f o Offset D. J. Jones, et al. Science 288, 635 (2000 ) Fourier transform of periodic signal discrete frequency components.

12. 12 Measurement of f r and f o f r can be measured with photo-detector in optical path Repetition Rate Offset 0 f 2n I(f)I(f) f fnfn frfr fofo 2f n -f 2n = 2(nf rep +f o ) - (2nf rep +f o ) = f 0 Octave Spanning - Microstructure fiber - Laser Cavity D. J. Jones, et al. Science 288, 635 (2000 )

13. 13 Frequency comb: state-of-the-art n = n f r  – f o Optical Synthesizer I( ) frfr f0f0 1/ f r =   o  +  oo Waveform control f r uniformity < 10 -18 Absolute inaccuracy < 10 -15 Short term instabilities ~ 10 -15 @ 1s Comb linewidth ~ 0.3 Hz  < 10 -2 rad, timing jitter < 1fs Ye & Cundiff, Eds., “ Comb ”, Springer (2005). Udem, Holzworth & Hänsch, Nature 416, 233 (2002). Visible Frequency (Hz) 10 10 11 10 12 10 13 10 14 10 15 Freq. comb 10 6 :1 Reduction Gear

14. 14 Comparison of Hz-linewidth lasers across the visible spectrum Laser 2 1064 nm Cavity 2 Laser 1 700 nm Cavity 1 Laser 1 Laser 2 Femto comb 30 m noise-cancelled fiber 35 m noise-cancelled fiber Ludlow et al., PRL 96, 033003(2006). Beat width: 3 Hz 20 Hz 5 Hz 4/11/ 2006

15. 15 Oscillator Counter  a Atoms New era for optical atomic clocks Diddams et al., Science 293, 825 (2001). Ye et al, Phys. Rev. Lett. 87, 270801 (2001). Feedback (accuracy) Ultrastable laser optical comb optical frequency synthesizer & counter RF or optical readout

16. 16 Spectroscopy with Combs 300 THz I(1)I(1) 1 300 THz band width and 100 MHz mode spacing. 3,000,000 modes with 0.3  W power 1 spectrosopy with a single mode hard but possible: V.Gerginov et al. Optics Letters, 30, 1734 (2005)

17. 17 Absolute Frequency of 87 Sr 1 S 0 – 3 P 0 March 2, 2006 FWHM 15 Hz Ludlow et al., Phys. Rev. Lett. 96, 033003 (2006). Accuracy soon reaching 1 x 10 -15 2005 2006 April, 2006 Q ~ 1 x 10 14 Projected stability < 1 x 10 -15 at 1 s

18. 18 Osnova vseh shem je fazno uklenjena zanka