摘要： The reduction in the group velocity of a light pulse due to a resonance is termed slow light. A velocity reduction to 17 m/s was demonstrated using electromagnetically induced transparency (EIT) [1]. It was later demonstrated that light could be stopped completely [2-3]. Whilst slow light EIT experiments have been ground breaking, they require a vapour cloud cooled close to 0 K. Here we present a possible alternative using gratings and a time-dependent refractive index. Slow light can be induced by a Bragg grating by propagating a pulse with a carrier frequency close to the rejection band created by the Bragg resonance. This is accompanied by a substantial increase in group velocity dispersion (GVD) causing significant pulse broadening and limiting practical uses. A Moiré grating, which is a superposition of two grating periods has been suggested as a potential solution to reduce GVD [4]. The two grating periods produce two rejection bands separated by a transmission band. Propagating a pulse through the transmission band induces slow light, but the GVD generated by one rejection band is compensated by the other. We have developed a parametrisation for the Moiré grating periods such that they produce a transmission band centred on a given carrier frequency. Further using the parametrisation, we have derived a set of modified coupled mode equations, describing the coupling of the amplitudes A and B of the forward and backward propagating light for gratings of strength (cid:78) and with (cid:47)s the Moiré period and (cid:39)b the detuning. Our numerical simulations of a frequency-resolved version of Eq. (1) confirm that Moiré gratings produce slow light with minimal pulse broadening. The bandwidth of the rejection bands is dependent on the strength of the grating which is controlled by the grating modulation ?n. As the grating strength is increased, the rejection bands broaden reducing the transmission gap. If the grating strength is increased sufficiently the transmission band will close. Figures 1(a) and (b) show simulations of pulse propagation through a Moiré grating using finite difference time domain (FDTD) methods. The group velocity is given by the gradient of propagation distance versus time. Figure 1(a) shows propagation for a time-independent ?n. In Figure 1(b), ?n is increased by a time-dependent refractive index [5]; at 190 ps ?n is increased so that the transmission gap closes and is decreased to its original value at 440 ps, reopening the transmission gap. Closing the transmission band whilst a pulse is propagating through the grating induces stopped light. The pulse becomes trapped and remains stationary within the grating until the grating strength is reduced and the pulse can continue to propagate, analogous to results achieved in EIT [2-3]. Figure 1(c) shows how the transmission band closes as a function of the grating modulation. While the realisation of a time-dependent Moiré grating remains challenging, it presents a versatile alternative to the storage and release of light pulses in a solid-state platform, which would provide an essential element for, e.g., quantum information processing.