Figure 4: The dual-focused two-photon.
From: On-chip steering of entangled photons in nonlinear photonic crystals
(a) The incident pump lies halfway between the two principal axes. Pj (j=0, ±1, ±2,...) are equivalent principal axes of the QPM two-photon lens. (b) Simulation of the coincidence count profile as a function of the propagation distance for the dual-focusing case. (c) Measured single (blue triangles) and coincidence (red dots) counts versus the transverse position of the fibre tip in the focal plane for the dual-focusing case. (d,e) Measured Fourier spectra of the multi-stripe parabolic PPLT for the single-focusing and dual-focusing case, respectively. The third-order reciprocal vectors used in the QPM are marked.
