Abstract:
The signals of the free-induction decay (FID) are detected in a $\mathrm{CdS}$ crystal at a wavelength of 790 nm under the condition of two-photon absorption of light quanta from different crossed femtosecond laser beams, with one photon being absorbed from a beam of wavevector $\mathbf k_1$, and the other photon from another beam of wavevector $\mathbf k_2$. FID-photons with wavelengths of 790 nm are emitted in two opposite directions and are correlated by frequencies, places and times of birth.