1. State Scientific Center of the Russian Federation National Research Institute for Physical-Technical and Radio Engineering Measurements Progress in deep laser cooling of Strontium at VNIIFTRI S. Strelkin, A. Galyshev, O. Berdasov, A. Gribov, S. Slyusarev P.N. Lebedev Physical Institute of the Russian Academy of Science K. Khabarova, N. Kolachevsky

2. GLONASS accuracy has significantly improved over last five years GLONASS Accuracy 8 years ago GLONASS allowed one to choose the appropriate street from the list… 3 years ago one knew exactly what the street it was.

3. Frequency standard’s evolution

4. M. Takamoto et al., PRL 102, 063002 (2009) 1D optical lattice and magic wave lengths

5. “An optical lattice clock with accuracy and stability at the 10 -18 level”, B.J.Bloom etc., Nature, vol 506, 6 Feb. 2014 Sr-87 optical lattice clock instability

6. Sr-87 optical lattice clock in Russia 2010 – Sr lattice clock project within GLONASS program has been started at VNIIFTRI 2011 – collaboration with P.N. Lebedev Physical Institute

7. Sr isotopes: 88 (81%), 87 (7%), 86 (10%), 84 (2%) Natural linewidth = 1 mHz (allowed by hyperfine coupling of 3 P 0 to 3 P 1 and 1 P 1 ) @ 698 nm Weak sensitivity to the magnetic field (J = 0 →J = 0 transition) Clock transition: 1 S 0 3 P 0 Sr electronic level diagram

8. 3D scatch of the vacuum system

9. Vertical set method of the system

10. Optical scheme detection beam Silver mirror Zeeman slower beam MOT beams oven PMT Zeeman slower camera

11. Without repumpers With repumpers ~10 6 ~4x10 7 First stage cooling

12. x10 more atoms with repumpers Repumping effect on trapped atoms number

13. Number of atoms in the “blue” MOT N~4*10 7 Т ~ 3 мК (depends on the intensity) 1 cm Temperature and number of atoms in the 1 st MOT

14. Narrower transition 1 S 0 3 P 1 is well-suited to Doppler cooling (@689 nm, natural linewidth 7,5 kHz, Doppler limit 200 nK) Narrower transition 1 S 0 3 P 1 is well-suited to Doppler cooling (@689 nm, natural linewidth 7,5 kHz, Doppler limit 200 nK) Narrow line requires narrow laser spectrum and high frequency stability Second stage cooling

15. Toptica DL pro laser system @689 nm Narrowing of the red MOT cooling laser

16. The distance covered during transportation - 60 km ULE systems manufacturing and transportation

17. Laser stabilization

18. Linear drift ~300 mHz/s Beatnotes

19. ULE-1 spacer: ATF films Finesse 60 000 ULE-2 spacer: Lebedev Physics Institute Finesse 45 000 ULE-1 and ULE-2 Critical Temperatures

20. Beatnote spectral linewidth

21. Doppler width of 1 S 0 - 3 P 1 transition @3 mK ~ 2 MHz Second stage cooling features

22. FM of cooling radiation allows to deal with different velocity groups within Doppler profile Broadband second stage cooling

23. 1 mm Broadband second stage cooling ~10 6

24. Retrapping efficiency: 8-10% Temperature in the end of broadband cooling: T~35  K Broadband second stage cooling

25. Retrapping efficiency High intensity in the first stage cooling leads to low retrapping efficiency BUT

26. Retrapping efficiency The number of atoms in the first MOT depends on the cooling light intensity

27. Atomic cloud in the end of the second stage cooling T=2  K N=10 5 Atomic cloud in the end of the second stage cooling T=2  K N=10 5 Single mode second stage  f=100 

28. g≈eg≈e 1D MOT standard configuration Atomic population in any ground state favors absorption of light from the appropriate direction for trapping. Red MOT Second stage cooling of 87 Sr

29.  g <<  e Absorption of light from a given direction depends on m F, and some m F states are thus not suited to provide spatial confinement in a MOT The need for stirring and randomizing the population among m F levels Trapping +Stirring Second stage cooling of 87 Sr

30. Clock laser systems

31. Target instability 1*10 -15 Finesse: 260 000 Achievable laser linewidth: ~1 Hz Clock laser systems

32. First stage cooling of 88 Sr and 87 Sr Two ULE stabilized lasers for second stage cooling are assembled and characterized Second stage cooling of 88 Sr Two ULE stabilized laser systems for clock transition spectroscopy are assembled Outlook Loading cooled atoms in the optical lattice at 813 nm and at 390 nm OPTICAL LATTICE CLOCK Conclusions

33. Working group at VNIIFTRI

34. Спасибо за внимание!