University of Zagreb. Faculty of Science. Department of Physics.
Abstract
U ovom diplomskom radu proučavano je istovremeno hlađenje dva izotopa rubidija, 85^Rb i 87^Rb, pomoću optičkog frekventnog češlja. U tu svrhu, razvila se magnetooptička stupica za atome 85^Rb te se dobiveni oblak preklopio s oblakom 87^Rb pripremljenim u prije razvijenoj magnetooptičkoj stupici za taj izotop. Ovako pripremljen sustav, predhlađen oblak atoma 85^Rb i 87^Rb, početna je točka za pokazivanje hlađenja frekventnim češljem. Određene su spektralne linije češlja koje u frekvencijama odgovaraju prijelazima korištenim za hlađenje atoma 85Rb i 87Rb te su tehnikom vremena proleta izmjerene temperature oba izotopa istovremeno. Pri tome je dobiveno da oba izotopa prate iste temperaturne trendove, odnosno da je na ovaj način moguće istovremeno hladiti dvije vrste atoma. Također, ispitano je kako vrijeme trajanja međudjelovanja frekventnog češlja sa atomima 85^Rb i 87^Rb utječe na postizanje konačnih temperatura. Zaključeno je da se nakon hlađenja frekventnim češljem u trajanju od nekoliko milisekundi postiže konačna temperatura atoma te da je ona iznosom bliska Dopplerovoj temperaturi.In this thesis, simultaneous cooling of two rubidium isotopes, 85^Rb and 87^Rb, using an optical frequency comb was studied. For that purpose, a magneto-optical trap for 85^Rb atoms was developed. The obtained cloud was overlapped with a 87^Rb cloud which was beforehand developed in a magneto-optical trap for that isotope. A precooled cloud of 85^Rb and 87^Rb atoms prepared in this way serves as a starting point for cooling with a frequency comb. Comb lines which, in terms of frequency, correspond to transitions used for cooling of 85^Rb and 87^Rb atoms, were determined. Temperatures of both isotopes were measured simultaneously using a time of flight method. Obtained temperatures showed same behaviour for both isotopes which led to the conclusion that it is indeed possible to simultaneously cool two atomic species using an optical frequency comb. In addition, temperature dependence of 85^Rb and 87^Rb atoms on the interaction time with the frequency comb was measured. Results showed that temperatures close to the Doppler limit are obtained on a time scale of few milliseconds, and do not change with further increasing the interaction time
