Effective regime of electromagnetically induced transparency in a Pr$^{3+}$:LaF$_3$ crystal

The results of experimental and numerical investigations of electromagnetically induced transparency in a Pr$^{3+}$:LaF$_3$ crystal have been presented. A spectrally isolated $\Lambda$ system has been made of a specially prepared medium of an ensemble of particles with an inhomogeneous width less than the hyperfine splitting of both upper and lower operating levels. A considerable increase in the transmittance with respect to an unprepared medium has been demonstrated. It has been shown that, under the experimental conditions, the transmittance is limited by the apparatus (spread of the transmission peak by the instrumental linewidth specified by the probe pulse length).