Development of a laser cooling and magneto-optical trapping experiment for Rubidium 87 atoms

Rigby, Charles Ian (Stellenbosch : University of Stellenbosch, 2011-03)

Thesis (MSc)--University of Stellenbosch, 2011.

Thesis

ENGLISH ABSTRACT: A magneto optical trap (MOT) is capable of trapping a vapor cloud consisting of atoms cooled down to the micro Kelvin range. Three orthogonal pairs of counter-propagating laser beams of the correct circular polarisation form an optical molasses which facilitates the cooling of neutral atoms. Additionally a spatially non-uniform magnetic field produced by two current carrying coils in a Maxwell gradient configuration is used to trap the cooled atoms. In this report the effects of the trap parameters, including the laser beam intensity and frequency detuning, beam diameter and magnetic field gradient, on the number of trapped atoms are discussed. Secondly the development of an experimental setup for laser cooling and trapping of 87Rb atoms in vacuum with the aid of a MOT is presented. All trap components were implemented and characterised. The vacuum system and trapping chamber in which the cooling takes place were designed and constructed. A rubidium getter to act as a source of atoms was integrated into the vacuum system. The two external cavity diode lasers used for trapping and optical re-pumping were characterised. The optical setup required for the optical molasses was designed, constructed and characterised. Saturated absorption spectroscopy was performed to investigate the hyperfine structure of 87Rb and to frequency lock the lasers. We report on the current status of the project with regards to progress, results and future work.

AFRIKAANSE OPSOMMING: 'n Magneto-optiese val (magneto optical trap, MOT) kan 'n dampwolk van atome vang en afkoel tot in die mikro Kelvin bereik. Drie ortogonale pare laserbundels, elke paar voortplantend in teenoorgestelde rigtings, met die korrekte sirkelvormige polarisasie vorm 'n sogenaamde optiese molasse wat die afkoeling van neutrale atome moontlik maak. Bykomend word 'n ruimtelik nie-uniforme magneetveld geproduseer deur twee stroomdraende spoele in 'n Maxwell gradient-opstelling gebruik om die afgekoelde atome te vang. In hierdie verslag word die invloed van die val parameters, insluitend die laserbundel intensiteit en frekwensie afstemming, die laserbundel deursnit en magneetveld gradiënt, op die aantal atome in die val bespreek. Tweedens word die ontwikkeling van 'n eksperimentele opstelling vir laser afkoeling en vang van 87Rb atome in vakuum met die hulp van 'n MOT voorgelê. Alle komponente van die val is geïmplementeer en gekarakteriseer. Die vakuumsisteem en val-kamer waarin die afkoeling plaasvind is ontwerp en gebou. 'n Rubidium gasbinder is in die vakuumsisteem ingebou om as 'n bron van atome te dien. Die twee eksterne resonator diodelasers wat gebruik is vir die val en die optiese terugpomp is gekarakteriseer. Die optiese opstelling wat nodig is vir die optiese molasse is ontwerp, gebou en gekarakteriseer. Versadigde absorpsiespektroskopie is uitgevoer om die hiperfynstruktuur van 87Rb te ondersoek en om die lasers se frekwensies te stabiliseer. Verslag word gedoen oor die huidige stand van die projek wat betref vordering, resultate en toekomstige werk.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/6492
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