Interference fringes in a nonlinear Michelson interferometer based on spontaneous parametric down-conversion

Quantum nonlinear interferometers (QNIs) can measure the infrared physical quantities of a sample by detecting visible photons. A QNI with Michelson geometry based on spontaneous parametric down-conversion in second-order crystal is studied systematically. simplified theoretical model presented. The interference visibility, coherence length, equal-inclination interference, and equal-thickness for are demonstrated theoretically experimentally. As an application example QNI, refractive index angle between two surfaces BBO measured using interference.