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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:30 |
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Conference: Bucharest University Faculty of Physics 2015 Meeting
Section: Solid State Physics and Materials Science
Title:
Exciton-phonon interaction in PbI2 layered structure as a stimulated Raman scattering
Authors:
Andreea-Alexandra NILA (1), M. BAIBARAC (1), I. BALTOG (1)
Affiliation:
1) National Institute of Material Physics, Laboratory of Optical Processes in Nanostructured Materials, PO Box MG-7, RO-77125, Bucharest, Romania
E-mail
andreea.nila@gmail.com
Keywords:
Resonant Raman scattering, photoluminescence, exciton-phonon interaction, layered crystals.
Abstract:
The enhancement of the Raman-scattered intensities of the vibrational modes predicted at 96 cm-1 and 220 cm-1, respectively, is experimentally investigated in different morphologies of PbI2 layered structures at low temperature under an excitation frequency which is close to the edge of the fundamental absorption band. The phenomenon that underlies Raman enhancement is based on exciton-phonon interaction and is a feature of stimulating Raman process that results from the coexistence of two coherent optical fields, the pumping laser light and the excitonic photoluminescence (PL), which behave as a super-radiant monochromatic emission light following the Poisson distribution. Relative to the electric vector of the excitation light, one observes that the different crystalline orientations show variation of the excitonic emission band, being more intense when optical vector is perpendicular with respect to the c-crystallographic axis. Depending on how excitation laser light superposes over the PL profile of the excitonic band, the energy transfer from exciton state towards the Raman lines reveals an enhancement which can occurs differently in the Stokes and anti-Stokes Raman branches and with different magnitudes for all Raman lines. According to the sample morphology, it is found that the Raman efficiency increases more in micrometric powders than in single crystal, being conditioned by the high light diffusion power of the material under the mixing of two optical fields which leads to a nonlinear optical effect with a strong enhancement of the Stokes and anti-Stokes Raman emissions.
References:
1. R. Zheng, M. Matsuura, Phys. Rev. B 56, 2058-2061 (1997);
2. M. Lange et all., Phys. Rev. B 86, 045318 (2012);
3. L. Pedesseau et all., Thin Solid Films 541, 9-11 (2013);
4. T. Baikie et all., J. Mater. Chem. A 1, 5628 (2013);
5. Y. R. Shen, The Principle of Nonlinear Optics, Hoboken, NJ: Wiley, pp.141 (2003).
Acknowledgement:
This work was supported by the Romanian research project PN09-45
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