Control of the frequency spectrum of a biphoton field due to the electro-optical effect

A method for controlling the spectrum of spontaneous parametric down-conversion has been implemented. This method is based on the application of the gradient of an electrostatic field to a nonlinear crystal where down-conversion occurs. Due to the electro-optical effect, i.e., the dependence of the refractive indices on the applied field, the phase-matching conditions are different along the length of the crystal and, as a result, the spectrum of the emitted biphoton field is modified.