``Entangled'' free-induction decay in CdS crystal under two-photon excitation by two crossed laser beams

Abstract

A new method of two-photon excitation of femtosecond signals of "entangled" free induction decay (EFID) by two crossed 790-nm laser beams in a CdS crystal at room temperature has been realized for the first time. This "entangled" (through the wave vectors) coherent response appears only in the case when the photons involved to the process of twophoton excitation of the sample belong to the different laser beams. This technique allows one to separate the EFID signal from the exciting femtosecond pulses and to vary the response wavelength by varying the angle between their wave vectors. The most optimal case occurs when the angle between the wave vectors of exciting pulses as well as the angle between each of these wave vectors and that of the response is equal to 60 • .

Femtosecond correlated photon echo in CdS crystal under two-photon excitation by two pairs of crossed laser beams

“…Where the notation 'CFID' stands for 'correlated free induction decay'. This expression coincides with final formula of [3]. Summing over the integrating over solid angle we obtain [10,11]…”

“…In Leontiev et al [3] the signals of the correlated free induction decay (CFID) generated in a CdS crystal under two-photon excitation by femtosecond 793 nm radiation of a Ti:sapphire laser at room temperature were predicted. Two laser beams propagating in the directions k 1 and k 2 at an angle of 60° to each other act on the same region of the CdS film inducing two gratings of nonequilibrium electric polarization − k k…”

Correlated stimulated photon echo signals under three-photon femtosecond excitation of CdSe–CdS colloidal quantum dots

“…In [5] we predicted the possibility of correlated free induction decay (CFID) signal generation under two-photon excitation of a CdS semiconductor crystal by femtosecond 800 nm radiation of a Ti:sapphire laser in the directions of wave vectors k 1 and k 2 oriented at an angle of 60° to each other. This optical transient phenomenon is formed in superposition states.…”

Correlated signals of cluster superfluorescence under two-and three-photon excitation of CdSe/CdS nanostructures

“…In our case, the situation is more complicated because of the two-and three-photon modes of the excitation by crossed femtosecond laser beams. The presence of the angle of 60° between the wavevectors of the first k1 and the second k2 exciting pulses leads, according to [7], to the emitting of the coherent CSF signals in the mutually opposite directions [8]. Earlier, in [9], it was experimentally shown that one needs the three-photon mode in order to excite the electrons of such structures by the radiation of this laser.…”