Electromagnetically induced transparency and dark fluorescence in a Y-type four-level diatomic sodium system
Li-Ren Liu1*, Yen-Cheng Lai1, Chin-Chun Tsai1
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
* presenting author:Li-Ren Liu, email:cilvaarne@hotmail.com
Two channels could affect the fluorescence signal of the upper level in a Y-type four-level diatomic sodium system: electromagnetically induced transparency (EIT) and population competition between two upper states. In this study, the excited state of sodium dimer was generated by using optical-optical double resonance (OODR) and the state-selected fluorescence of the excited state was measured by using a monochromator. When a strong coupling field couples the intermediate level Β¹Πu(v=13,J=74) to the upper level 3¹Πg(v=8,J=75) of sodium dimer, a sharp dip appears in the middle of the state-selected signal due to EIT effect under a weak resonance probe field with transition of the ground state Χ¹Σg(v=15,J=73) to the intermediate state Β¹Πu(v=13,J=74). In a Y-type four-level diatomic sodium system, another upper state 3¹Πg(v=9,J=73) was employed by using all-optical triple resonance (AOTR), the competition between population enhancement and quantum interference in this system was demonstrated. The occurrences of EIT or dark fluorescence were analyzed in the basis of three-level cascade system under different Rabi frequency of the coupling fields using density matrix method.

Keywords: electromagnetically induced transparency, dark fluorescence, diatomic sodium