| Summary: | 碩士 === 國立清華大學 === 物理學系 === 93 === Laser cooling has been developed rapidly in rent years. Then, laser cooling has became an important tool in research. Since laser cooling was proposed in 1975, techniques of cooling such as magneto-optical trap, polarization gradient cooling and evaporative cooling were developed. The trapped atoms can be cooled below 500 pK. Bose-Einstein condensation was achieved because of laser cooling. Besides atomic and molecular physics, laser cooling is applied to condensed matter physics, plasma physics and quantum computing.
A system of magneto-optical trap has been set up in our laboratory. The system can be switched to as a 39K or 87Rb MOT. The system is mainly composed of a home-made Ti:sapphire laser and a diode laser(DL100). The Ti:sapphire laser has an output power of 430 mW pumped by a 5W DPSS green laser. The gradient of magnetic field of MOT is about 20 g/cm.
We trapped potassium and rubidium with this system by slowly scanning the frequency of the trapping laser. Saturation spectroscopy and FM spectroscopy of D1 transition of 39K , D2 transition of 39K and D2 transition of 87Rb were observed. Our MOT system could be improved to trap rubidium and potassium simultaneously by adding another Ti: sapphire laser. Ultracold mixture of atomic rubidium and potassium will be studied with such an improved system.
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