## 1 Introduction  
Coherent manipulation of the optical fields and material properties via the quantum interference effect is an important issue in both fundamental physics and applied physics. The electromagnetically-induced transparency (EIT) effect [1; 2; 3] is the result of destructive quantum interference among different atomic transitions and is an effective way of modifying the material properties and manipulating the light fields. The absorption of EIT media, even when the light field is resonantly applied on the atomic transition, will be significantly reduced or even eliminated under the two-photon resonant condition. Yet, the EIT effect is different from the Autler-Townes splitting which originates from energy level splitting due to strong field-driven interactions [4; 5; 6; 7]. The EIT effect is accompanied by a strong spectral dispersion of materials, which leads to slow light [8]. There are various ways to generate slow light, for instance, through the EIT effect [8; 9; 10; 11], the atomic frequency comb [12; 13; 14], the photorefractive wave-mixing [15; 16], coherent population oscillations [17; 18], stimulated Raman scattering [19] and stimulated Brillouin scattering [20], and so on. Nevertheless, the EIT effect is also capable of storing light pluses or quantum states of photons by simply halting the light pulses; therefore, it has various potential applications in both classical optics and quantum optics [9; 10]. [PERSON] et al. [21] demonstrated the storage and retrieval of light pulses in a cold cloud of sodium atoms, and [PERSON] et al. [22] reported the light pulse storage in Pr\({}^{3+}\)-doped\(\mathrm{Y_{2}SiO_{5}}\) (Pr:YSO) crystal. The storage and retrieval of transverse multimode images was achieved in hot atomic rubidium vapor by [PERSON] et al. [23], and the multiplexing storage of light pules was also demonstrated in Pr:YSO crystal by [PERSON] et al. [24]. In addition, storage of the quantum state of light, such as a single photon and entangled photon pairs, was demonstrated [25; 26; 27; 28]. More recently, highly efficient coherent optical memory with a storage efficiency of 92% and a time-bandwidth product of 1200 was reported by [PERSON] et al. in Cs atomic vapor [29]. In addition, the influences from the environment of the atomic ensemble, such as the buffer gas in the atomic vapor, the substrates in EIT solids and the cavity confinement, on the EIT effect and EIT-based photon propagation and storage were studied intensively [30; 31]. EIT analogies in artificial systems other than the atomic ensemble, such as superconducting quantum circuits and whispering-gallery microcavities, were explored in detail, which was motivated by potential applications in quantum information processing [5; 32; 33; 34]. The EIT effect can also be used to manipulate the light fields and to generate new optical fields with novel spatial structures or properties. [PERSON] et al. [35] generated nonclassical photon pairs through collective emission from a cloud of cold Cs atoms. [PERSON] et al. [25] generated a single photon with tunable frequency, timing and bandwidth in Rb atomic vapors based on the EIT effect. The intensity dependence of the EIT effect was used to suppress the light diffraction to achieve a super-resolved image [36; 37; 38], optical diffraction in the momentum space and atomic diffusion caused by the thermal atomic motion of atomic vapors [39; 40]. In addition, special phase structures, such as optical vortexes, could be stored and manipulated in EIT media [41; 42; 43], even at the single photon level [28], which has great practical application in optical communications and quantum information processing. It was realized, even in the early stages, that the EIT effect can enhance nonlinear optical effects. [PERSON] et al. [1] showed theoretically that third-order susceptibility can be resonantly enhanced in EIT media, which was soon experimentally verified in both atomic vapors and solids, such as Pr:YSO crystal [44; 45; 46; 47; 48].