11 June 2002 Dynamics of stimulated emission and coherent backscattering of light from amplifying random medium
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Proceedings Volume 4643, Ultrafast Phenomena in Semiconductors VI; (2002) https://doi.org/10.1117/12.470419
Event: Symposium on Integrated Optoelectronic Devices, 2002, San Jose, California, United States
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.
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Kam Sing Wong, Tao Sun, George K.L. Wong, "Dynamics of stimulated emission and coherent backscattering of light from amplifying random medium", Proc. SPIE 4643, Ultrafast Phenomena in Semiconductors VI, (11 June 2002); doi: 10.1117/12.470419; https://doi.org/10.1117/12.470419
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