The Inversionless Amplification in a Tripod System of ⁸⁷Rb Atoms in a Magneto-optical Trap

The probe transmission spectra around the atomic transition 5²S_1/2,F=2→5²P_3/2,F'=2 of ⁸⁷Rb are measured in a magneto-optical trap by adding a coupling field around the atomic transition 5²S_1/2,F=2→5²P_3/2,F'=2. The inversionless amplification is observed in the spectrum over the atomic transition 5²S_1/2,F=2→5²P_3/2,F'=2. The tripod electromagnetically induced transparency is proposed to account for the amplification feature, in which population distributions among these related atomic levels play an important role.