band shown in Fig. 4(e) and contributing in the expansion (5) have such a behavior. This effect is in fact more pronounced along directions oriented with polar angles θ = φ$_{s}$ ± π/ 2 being the stationary point φ$_{s}$ = ± 41 deg ( θ = ± 49 deg) associated with the self-collimation effect. Although superresolution along the x -axis is modest in comparison with that obtained in the y -axis, we wonder if beamwidths might surpass the diffraction limit in all directions. As resolved in Sec. III, for our examples where β$_{max}$ = 19 . 42 µ m − 1 and λ$_{0}$ = 550 nm this diffraction limit reads Δ$_{min}$ = 116 nm. In Fig. 9 we represent the intensity distribution | h$_{x}$ | 2 of a nondiffracting beam excited with a transverse spatial frequency γ = 17 . 20 µ m − 1 giving a propagation constant β = 9 . 00 µ m − $^{1}$. In this case the central peak is anamorphic and characterized by FWHMs Δ$_{x}$ = 109 nm and Δ$_{y}$ = 46 nm all below the diffraction limit. The bandgap-induced filtering also leads to intense sidelobes along the interface y = 0, however they decay as going beyond the focus. Moreover, the peak intensity of these secondary foci cannot exceed that intensity of the main focus. We have demonstrated that diffraction-free beams propagating in structured media com- posed of alternating layers of positive and negative ϵ may reach beamsizes surpassing the diffraction limit. For an excitation of the form given in (26), we recall that this limit is attained when the transverse spatial frequency is maximum, γ$_{max}$ = √$_{¯}$ ϵ$_{d}$ω/c , leading to stationary ( β = 0) Bessel waves with a central spot of FWHM Δ$_{min}$ = 2 . 253 /γ$_{max}$ . In the layered system, two different mechanisms lead to the superresolving effect. A bandpass filtering due to the existence of gaps in the spatial spectrum of k$_{x}$ modifies the response of the system transversally providing a narrow peak along the x -axis with moderate gain (Δ$_{x}$ < ∼ Δ$_{min}$) and high sidelobes (secondary foci). In the direction of the periodicity, however, superresolution is carried out by the formation of surface resonances in the metal-dielectric interfaces leading to fast decays out of these planes. In our numerical simulations, Δ$_{y}$ can be as low as a third of Δ$_{min}$. Additionally, dephase of Bloch constituents belonging to different bands contributes to the growth control of secondary foci in nearby surfaces. In principle, subwavelength beamwidths along an infinitely long distance might poten- tially be obtained. However practical limitations in the geometry of the system leads to the 16 VI. CONCLUDING REMARKS