State Scientific Center of the Russian Federation

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

2. 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. GLONASS accuracy has significantly improved over last five years

3. Frequency standard’s evolution

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

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

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 electronic level diagram Sr isotopes: 88 (81%), 87 (7%), 86 (10%), 84 (2%) Clock transition: 1S0 3P0 Natural linewidth = 1 mHz(allowed by hyperfine coupling of 3P0 to 3P1 and 1P1) @ 698 nm Weak sensitivity to the magnetic field (J = 0 →J = 0 transition)

8. 3D scatch of the vacuum system

9. Vertical set method of the system

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

11. Firststagecooling ~106 Without repumpers ~4x107 With repumpers

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

13. Temperature and number of atoms in the 1st MOT 1 cm Number of atoms in the “blue” MOTN~4*107 Т ~ 3 мК (depends on the intensity)

14. Secondstagecooling Narrower transition 1S03P1 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

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

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

17. Laser stabilization

18. Beatnotes Linear drift ~300 mHz/s

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

20. Beatnote spectral linewidth

21. Second stage cooling features Doppler width of 1S0-3P1 transition @3 mK ~ 2 MHz

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

23. Broadband second stage cooling 1 mm ~106

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

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. Single mode second stage Atomic cloud in the end of the second stage cooling T=2 mK N=105 Df=100 g

28. Clock laser systems

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

30. Conclusions • First stage cooling of 88Sr and 87Sr • Two ULE stabilized lasers for second stage cooling are assembled and characterized • Second stage cooling of 88Sr • 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

31. Working group at VNIIFTRI

32. Спасибо за внимание!