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The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs.

Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Spontaneous density grating formation in suspensions of dielectric nanoparticles

Wiggins, Mark and Robb, Gordon and McNeil, Brian and Jones, David and Jamison, Steven and Jaroszynski, Dino (2002) Spontaneous density grating formation in suspensions of dielectric nanoparticles. Journal of Modern Optics, 49 (5-6). pp. 997-1006.

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Abstract

Experimental evidence for nonlinear optical behaviour due to the spontaneous formation of wavelength-scale density modulations or gratings in suspensions of dielectric particles is presented. A collection of dielectric particles pumped by a coherent radiation field may simultaneously form a density grating on the scale of the radiation wavelength and a coherently backscattered radiation field. The particle density grating is generated as a result of a periodic ponderomotive potential formed by the interference of the pump and backscattered fields. The experiment used a water suspension of latex microspheres (radius ≈ 56nm) pumped by a green CW laser (532nm, power ≤ 5W). A theoretical model of collective scattering of light from dielectric particles has been extended to include the effects of viscous and Brownian forces on the particles. This model predicts a small degree of particle bunching from which coherent backscattering of the pump occurs. The results of the theoretical model compare favourably with the experimental evidence. The relation between the results presented here and the phenomenon of Collective Rayleigh Scattering (CRS) is discussed.