Characterisation of grating properties for MOTs at multiple wavelengths and laser cooling Rb on the 5S1/2 - 6P3/2 transition at 420nm

  • Wenbo Li

Student thesis: Master's Thesis


This thesis presents progress towards making a blue magnetic-optical trap (MOT) utilizing a reflective diffraction grating, a 780nm and a 420nm laser. Taking advantage of the narrower line width of the 6P3/2 state, 420nm lasers can theoretically make a factor of 10 colder MOT than those using 780nm ones based on the Doppler limit. However, considering the low capture rate caused by this narrower linewidth, 87Rb atoms are planned to be captured using a MOT on the 5S1/2 - 5P3/2 transition at 780nm for pre-cooling and then transferred to a MOT on the 5S1/2 - 6P3/2 transition at 420nm. As the very first group intending to make a 420nm grating-MOT, we studied the behaviour (diffraction efficiency, polarisation efficiency) of diffraction gratings with different etch depth, coating material, duty cycle to find suitable gratings which work for both 780nm and 420 nm. To investigate other potential laser sources, 423nm laser diode samples were tested to explore the possibility of reaching the desired wavelength (420.297 nm) for cooling.
Date of Award20 Apr 2018
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorAidan Arnold (Supervisor) & Paul Griffin (Supervisor)

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