In recent years,there has been a significant surge of research activities on wave propagation in highly resonant media.Taking advantage of the conventional electromagnetically induced transparency technique,people have succeeded in enhancing Kerr nonlinearity of materials and realized a lot of nonlinear optical processes under weak driving conditions.On the other hand,wave propagations in such a highly resonant optical medium display many striking features.One of the most noticible cases is the effect of significant reduction of the group velocity of a wave packet due to the modification of medium dispersion properties.Such ultraslow propagation of optical fields has been shown to lead to several new physical effects that are important from both fundamental physics and technology view point.Particularly,well-characterized and distortion free ultraslow optical waves may lead to important implication such as high fidelity optical buffers,phase shifters,transmission lines,switches,routers and wavelength converters.This is the reason why ultraslow propagation of optical waves have been vigorously pursued in both field of fundamental research and technological development.