Fig. 1. (a) Reflected field and (b) spectrum of a pulse with A=2π, τp=5  fs incident on a periodic structure with δ=λ0/2, L=45  μm and ωc=0.05  fs−1. The dashed and dotted lines correspond to the leading and tail parts of the reflected fields, respectively.

Fig. 2. (a) Time evolution of Ω(t) and u(t) in a resonance medium with ωp=ω0. (b) The changing curves of χ′, χ′′, and n versus Δ in the case of (a). (c) Same as that for (b), but for a detuning medium with ωp=2ω0. (d) The reflected spectrum under the same parameters as (c). The other parameters are same as those in Fig. 1.

Fig. 3. A=2π, τp=5  fs, L=45  μm, ωc=0.05  fs−1. The reflected spectra of the periodic structures with δ=kλ0(k=2,1,1/4).

Fig. 4. (a)–(e) The reflected spectra of the periodic structures with δ=kλ0(k=2,1,1/2,1/4,1/8). A=4π, ωc=0.2  fs−1, L=150  μm. The other parameters are same as Fig. 3. The dashed line in (a) indicates the reflected spectrum of a bulk medium. (f) The scaling law of the frequency intervals of the spectral spikes against k.

Fig. 5. Comparison of the reflected spectra of ωc=0.01  fs−1 (solid line) and ωc=0.05  fs−1 (dashed line).