QUANTUM INTERFERENCE PHENOMENON IN THE COLD ATOMIC CASCADE SYSTEM

Author Institution: Department of Physics, National Cheng-Kung University, Tainan 70101,Taiwan(R.O.C.); Department of Physics, National Cheng-Kung University, Tainan 70101, Taiwan(R.O.C.); Department of Physics, National Cheng-Kung University, Tainan 70101, Taiwan(R.O.C.); Department of Physics, National Cheng-Kung University, Tainan 70101, Taiwan(R.O.C.)By using the technique of electromagnetically induced transparency(EIT), we have observed the quantum interference phenomenon in the lower-lying atomic Rydberg states of cold Cs atom in a magneto-optical trap (MOT) with typical atom numbers up to $1\times 10^{7}$, and cloud temperature about 100$\mu$K. In our experiments, a grating feedback diode laser is frequency stabilized on the Cs atom via Doppler-free saturation absorption transition $\ 6s ^{2}S_{1/2}, F=4> \rightarrow 6p ^{2}P_{3/2} , F^{\prime }=5>$, and a tunable Ti:Sapphire laser scans across the $\ 6p ^{2}P_{3/2}, F^{\prime }=5> \rightarrow 8s ^{2}S_{1/2}, F^{\prime\prime }=4>$ transition frequency. Both spontaneous emission fluorescence from MOT and transmission intensity of the diode laser are monitored. A subnatural linewidth signal is obtained for probing the transition of Cs $\ 6p ^{2}P_{3/2}, F^{\prime }=5> \rightarrow 8s ^{2}S_{1/2}, F^{\prime\prime }=4>$. These signals correspond to the cascade EIT among the$\ 6s ^{2}S_{1/2}, F=4> \leftrightarrow 6p ^{2}P_{3/2}, F^{\prime }=5>\leftrightarrow 8s ^{2}S_{1/2}, F^{\prime\prime }=4 >$. \vspace{1em} This project is financially sponsored by National Science Council (grand no. NSC-95-2112-M-012-MY3). \vspace{5em