Atomic coherence in laser spectroscopy and atom optics

In order to investigate effects of coherent population trapping (CPT) on electromagnetically induced transparency (EIT), we added an external weak magnetic field to identify a quantization axis. The laser beam whose polarization is parallel to the direction of the external magnetic field and the perpendicular laser are coupled to different transitions. CPT generated by two circular polarization components of the strong coupling beam when the polarization was perpendicular to the quantization axis, was competed with (EIT) so that absorption reduction could be larger than the case without CPT. We investigated the mechanism of steady-state light amplification without inversion using an incoherent pumping laser.