cooling Laurent Hilico Be energy levels 31313 nm Raman sideband cooling 2 counter propagating phase coherent beams 1 resonant beam 1 Raman laser AOM system ID: 1006587
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1. Cooling lasers and ion coolingLaurent Hilico
2. Be+ energy levels313.13 nmRaman sideband cooling2 counter-propagating phase-coherent beams1 resonant beam1 « Raman » laser + AOM systemDoppler laserDoppler cooling2 frequencies separated by 1.25 GHz1 laser and sidebands produced by an EOM
3. Fiber lasers for 626 nmRidge waveguide PPLN converterLaser n° 2714 mm560 mm600 mm1549 nm1050 nm626 nm2 systemsRaman1550 (4.5 W) + 1050 (4.5 W) → 626 nm (2 W)Doppler1549 (2 W) + 1050 (2 W) -> 626 (400 mW ?)13 U 19’’ rack5-10 m fiber
4. 626 nm DBR laser diode sourceF. Braun Institute Berlin, DBR laser diodes, ~50 mW at 626 nm, awfull modeInjection locking of a Fabry-Perot diode, ~100 mW at 626 nm, nice modeComparisonFiber laser narrow linewidth (< 50 kHz in the UV), easy to frequency control, remote control, expensiveDBR diode laser cheaper, broader linewidth (1,4 MHz in the UV), to be tightly locked
5. SHG cavities626 nm313 nm
6. Doppler and Raman beamsDopplerRamanSHG cavityEOMAOMON/OFFIntensity controlSHG cavityBeam splitterDouble pass AOM 312,5 MHzDouble pass AOM 312,5 MHzPhase coherent Raman beams separated by 1,25 GHzCapture trapPrecision trapPrecision trap
7. On the to do listBuild a new SHG cavity for the second laserImplement the double pass AOM systemsFind money for a second fiber laser systemBuy UV optical fibers to couple to the vacuum chamberWe have the optical componentsWe have the AOM’s and drivers
8. UV optical fibers, the recipesPurchase NKT fibers or Xblue fibers, photonic band gap fibersLoad with H2 (1-2 weeks under 100-200 Bar)Collapse the endsPut in the fridge (-20°… -80°C)Take the length you needCut, polish, collapse the endsConnectorizeExpose to UV (313 nm)That’s doneBuy a patch cord with the desired length (with connectors)Load with H2Put in the fridgeExpose to UVThat’s doneH2 chemically cure the defects that could become colored-center under UV irradiation and make the fiber absorbingSimple diffusion process of H2 into SiO2.10 µmNKT LMA-10UVAlphanov in BordeauxSeveral companiesAOS DresdenLab in Bordeaux…
9. Optical fibers Transmission > 70%, losses dominated by insertion lossesStable in time other months at 313 nmMethod also tested at 280 nm, 235 nmCollimators to be purged by clean N2, teflon tubes recommanded On the to do listContact Alphanov (Bordeaux) or Glophotonics (Limoges)Get few fibersCure them with our 313 nm and test the result~130 dB/km or 0.13 dB/m
10. Ion cooling status Paris LKB Be+ Doppler Cooling Paris LKB Be+/H2+ sympathetic Doppler cooling (9/2) Paris MPQ Sr+/Be+ sympathetic Doppler cooling (87/9) Mainz Ca+ Doppler Cooling Mainz single Ca+ ground state Raman sideband cooling Mainz Ca+/Be+ ion pair ground state Raman sideband coolingPulse sequence management using FPGA based electronics
11. ConclusionCooling almost doneWe go for optical fibers at 313 nm
12. 1 pixel = 2 µm