Fig. 1: The design of the PPLN waveguide module and the measured spectra of created photons in the module.
From: High-performance quantum entanglement generation via cascaded second-order nonlinear processes
a The design of the PPLN waveguide module. The input pump photons at λp pass through the filter (F1), with the input noise photons removed. The SpRS process takes place in the two fiber pigtails, while the cascaded SHG/SPDC processes occur in the PPLN waveguide. After filter (F2), the residual pump light is smaller than the input one by about ~ 20 dB, which could reduce the SpRS noise photons by ~ 100 times in per unit length of the fiber. b Measured spectra of correlated photon-pairs with phase matching. c and d are the measured co- and cross-polarized Raman spectra in the PPLN waveguide module under the phase mismatching condition.
