Quantum Interferences and Lasing without inversion

Reuben Shuker

Quantum-interference-related phenomena have great interest in many aspects of physics. Quantum interference between two independent quantum channels in three-level systems gives rise to various coherent phenomena, such as electromagnetically induced transparency (EIT), coherent population trapping (CPT), lasing/gain without inversion (LWI/GWI), enhancement of refraction index, sub- and super-luminal light propagation etc. These quantum-interference-related phenomena open a wide-range perspective for new type of phase-sensitive spectroscopy. In particular, the movie in Fig.1 shows the absorption/dispersion properties of the atom controlled by various parameters. Another example is the possibility to get sub-natural line widths (see movie in Fig.2).
 

Figure 1: Phase-controlled absorption (red) and dispersion (blue).	Figure 2: Sub-natural-width peak.