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A theoretical investigation is performed for the possibility and conditions of the stimulated induction of excitons in a thin layer of semiconductor quantum dots upon excitation by continuous-wave laser radiation.

We discuss the possibility of exciting a stimulated excitonic induction in a thin film of semiconductor quantum dots and analyze the possibility of writing and reading out the two-quantum excitonic transient holograms in such samples.

The possibility and conditions of an incoherent exciton echo excitation in a thin layer of the CdSe/CdS/ZnS semiconductor quantum dots spread on a glass substrate are discussed.

Entangled free induction decay (EFID) femtosecond signals are experimentally observed for the first time at a wavelength of 790 nm in a cadmium sulfide (CdS) crystal in the two-photon absorption (TPA) regime upon excitation by two crossed (angle, 60°) laser beams. The sample emitted two EFID signals simultaneously in opposite directions. The signals were diffracted by nonequilibrium electric polarization gratings induced by two laser beams in accordance with the laws of energy and momentum conservation. The possibility of exciting EFID signals in the three-photon absorption regime is discussed.

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 two-photon 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°.

The results of an experimental investigation of the incoherent photon echo in ruby (with Cr3+ concentration equal to 0.16 wt%) at T=1.7 K are presented. Optical fiber with length 3 m and diameter 100 μm was used for delivery of the first exciting pulse to a sample. The dependence of the IPE intensity on the excitation wavelength within the width of R1 absorption line was studied. The IPE decay curve was obtained and the phase relaxation time was found to be equal to 98 ns.

The possibility of an observation of correlated signals of the accumulated photon echo under a three-photon excitation of a sample, which is an ensemble of semiconductor nanoparticles of "core – shell" type, by a femtosecond radiation of Ti:Sa laser is discussed. The phase matching conditions of such signals are obtained.

The possibility and conditions for generation of the correlated signals of cluster superfluorescence (CSF) under two and three-quantum excitation of nanostructured samples CdSe/CdS by two crossed at the angle of 60° femtosecond beams of the Ti:Sapphire laser radiation are investigated. It is shown that intensity of the CSF signals is proportional to the cube of the number of clusters and that these collective signals are generated in mutually opposite directions k 1 – k 2 and k 2 – k 1 , where k 1 , k 2 are the wavevectors of the exciting pulses.

The possibility and conditions of the correlated signals of stimulated photon echo (SPE) generation under three-photon femtosecond excitation of a sample, which is an ensemble of N semiconductor nanoparticles, are investigated. Each of these nonoparticles consists of a CdSe core covered by a CdS shell. The phase matching conditions for correlated SPE signal formation in such a sample are obtained.

We consider the possibility of observing a femtosecond correlated photon echo (FCPE) under two-photon excitation of CdS crystal by two pairs of crossed laser beams. The peculiarities of FCPE signals and their possible applications are discussed.

Triggering optical superradiance, which allows a control of spontaneous emission with the use of an injection optical pulse, is considered. The multipulse regime of excitation of optical superradiance and the long-lived optical superradiance are analyzed as the generalizations of the triggering regime of superradiance excitation.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.