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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:32 |
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Conference: Bucharest University Faculty of Physics 2016 Meeting
Section: Solid State Physics and Materials Science
Title:
Exciton-Phonon Interaction as a Nonlinear Optical Process in Different Morphological Forms and Mixtures of Semiconductors
Authors:
Andreea NILA(1,2), M. BAIBARAC(2), I. BALTOG(2)
Affiliation:
1)University of Bucharest, Faculty of Physics, 077125 Magurele-Ilfov
2)National Institute of Material Physics, R-77125 Magurele-Ilfov
E-mail
andreea.nila@gmail.com
Keywords:
Exciton-phonon interaction, Stimulated Raman scattering, Wave mixing
Abstract:
Resonant Raman scattering performed on PbI2 and CdS as powder and single crystal morphological forms reveals a strong exciton-phonon interaction at low temperatures which is conditioned on the coexistence of two coherent optical fields that mix together, the incident laser light and the excitonic photoluminescence (PL) light, which in turn behaves as a coherent light source following the Poisson distribution. The key condition to achieve a higher efficiency of the mixing lights is to ensure a longer path of lights inside the matter, from which results higher geometrical mixing of the involved lights in powder sample than in the single crystal morphological form. Therefore, the exciton-phonon interaction manifests itself as a Stimulated Raman Scattering (SRS) process revealed by a strong enhancement of the Raman intensity with a stronger wave mixing in the powder, where each particle is simultaneously subjected to the mixing optical fields. In the context of exciton-phonon interaction, the following question arises: if the transfer of the energy from the excitonic PL towards the phonon Raman spectrum can be located in the same material or it could operate also in composites of two powders materials, as heterojunctions, in which the excitonic PL is associated to one component and the enhancement of Raman spectrum takes place in the other component? The answer is given by considering two mixtures of PbI2:Si and CdS:Si, being demonstrated that the exciton-phonon interaction can exist also in heterostructures, where the excitonic PL is generated only in PbI2 and CdS.
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