have been presented in the last few years to achieve single-photon blockade in solid-state systems with *resonant* Kerr-type nonlinearities, such as fully confined polariton boxes below the diffraction limit [@ciuti06prb; @gerace_josephson; @carusot2010epl; @ferretti2010; @savona10prl; @bamba]. In the latter, the Coulomb interaction of electron-hole pairs in a semiconductor or insulating resonant medium is responsible for a Kerr-type nonlinear coefficient, potentially able to produce photon blockade. Owing to experimental difficulties in reaching diffraction-limited polariton confinement with sufficiently large cavity lifetime, no evidence of quantum nonlinear behavior from these systems has been reported, yet. Besides this, applications of such devices as SPS in integrated quantum photonics technologies might be limited in the long term by lack of suitable active media in the telecom-band, necessary to be interfaced with long-distance communication networks, and the commonly cryogenic working temperatures [@focus_sps].

The possibility to engineer a SPS based on single-photon blockade from *non resonant* Kerr-type nonlinearities in passive devices (such as nano-structured silicon or GaAs platforms in the near infrared) could represent a breakthrough from quantum photonics perspectives. First, it would allow large flexibility on the operational wavelengths, to be engineered in the telecom band by the photonic confinement in the materials transparency window. Second, it 