r - a  [nm] (a) (b) (c) N cav P e g cav (2) FIG. 3: Mean photon number N$_{cav}$ , second-order photon correlation function g (2) $_{cav}$, and atomic excited-state population P$_{e}$ as functions of the atom-to-surface distance r − a . The input probe power is P$_{in}$ = 10 pW. The FBG cavity length is L = 10 cm. The frequencies of the probe field, the cavity, and the atom in free space are equal, i.e. ω$_{p}$ = ω$_{c}$ = ω$_{0}$ . The axial position z of the atom corresponds to an antinode of the cavity standing-wave field. Other parameters are as in Fig. 2. second-order photon correlation function g (2) cav increases with decreasing r − a . However, in the region of small r − a , where the van der Waals potential is significant, g (2) cav decreases with decreasing r − a . Thus, the r dependence of g (2) cav is basically opposite to that of N$_{cav}$ . Note that in the vicinity around the distance r − a = 70 nm, the correlation function g (2) cav can become larger than 2, that is, the photon distribution of the guided cavity field can become broader than the Boltzmann distribution for thermal states. We plot in Fig. 4 the mean photon number N$_{cav}$ , the second-order photon correlation function g (2) $_{cav}$, and the atomic excited-state population P$_{e}$ as functions of the axial position z of the atom along the fiber. Figure 4(a) shows that N$_{cav}$ has minima and maxima at the antinodes and the nodes of the cavity standing-wave field, respectively. It is clear that, in the fiber axial direction, N$_{cav}$ follows the spatial oscillations of the coupling coefficient G [see Eq. (33)]. Figure 4(b) shows that g (2) cav has maxima at the antinodes of the guided cavity field. The figure also shows that g (2) cav > 1, that is, the photon statistics is super-Poissonian, in a broad region around each antinode, and that g (2) cav ∼ = 1, that is, the photon statistics is almost Poissonian, in a smaller region around each node. A careful look at the data reveals that g (2) cav < 1, that is, the photon statistics is sub-Poissonian, when the position of the atom is slightly deviated from a node. The appearance of such a nonclassical state is related 15