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Proceedings Paper

Dynamics of stimulated emission and coherent backscattering of light from amplifying random medium
Author(s): Kam Sing Wong; Tao Sun; George K.L. Wong
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Paper Abstract

We investigated random scattering of light in a disorder gain medium of ZnO powder using the pump-probe technique. Using a probe beam at (lambda) =390nm, the width ((theta) ) of the coherent backscattering peak from the ZnO powder is measured to be ~7.5 degree(s), thus the coherent scattering length l is approximately 1.2(lambda) ((theta) =(lambda) /2(pi) l) which is close to the strong scattering regime. When a pump beam ((lambda) =267nm) exceeds a certain excitation threshold, supernarrow emission peaks (bandwidth less than 1nm) emerged from the ZnO broad photoluminescence background. Concurrently, we also observed enhancement and sharpening of the coherent backscattering cone. Since light from the center of the backscatter cone experience the largest number of scatterings (i.e. longest gain length), this result is thus consistent with the random laser model that the supernarrow peak is due to amplification and stimulated emission of photon in the random gain medium. The time-resolved pump-probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which is consistent with the interpretation that the supernarrow peaks are due to stimulated emission.

Paper Details

Date Published: 11 June 2002
PDF: 8 pages
Proc. SPIE 4643, Ultrafast Phenomena in Semiconductors VI, (11 June 2002); doi: 10.1117/12.470419
Show Author Affiliations
Kam Sing Wong, Hong Kong Univ. of Science and Technology (Hong Kong)
Tao Sun, Hong Kong Univ. of Science and Technology (Hong Kong)
George K.L. Wong, Hong Kong Univ. of Science and Technology (Hong Kong)

Published in SPIE Proceedings Vol. 4643:
Ultrafast Phenomena in Semiconductors VI
Kong-Thon F. Tsen; Jin-Joo Song; Hongxing Jiang, Editor(s)

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