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SUMMARY:Optical force and torque on a spheroid: Generalized Lorenz Mie The
 ory - Dr Feng Xu\, TU Darmstadt\, Germany
DTSTART:20080623T133000Z
DTEND:20080623T143000Z
UID:TALK12524@talks.cam.ac.uk
CONTACT:Jurij Kotar
DESCRIPTION:Radiation force induced by a laser beam has been widely utiliz
 ed to trap or to manipulate the particles of micrometer and nanometer scal
 e over the past 30 years. Various experimental instruments\, e.g. optical 
 tweezers and optical stretcher\, have been developed to meet the requireme
 nts of non-intrusive detection and control of the micro-objects\, e.g. dro
 plets\, cells\, and DNA strands. Regarding the theoretical aspect\, the Lo
 renz-Mie theory has been extended to deal with the case of non-plane wave 
 illumination and the force exerted on a sphere by a focused laser beam has
  been analytically predicted. Such a theory\, referred as generalized Lore
 nz-Mie theory (GLMT) has the potential to be further extended to some regu
 larly shaped particles when the incident beam is expanded in the coordinat
 es mirroring the geometry of these particles\, as exemplified by our previ
 ous work on scattering\, net force and torque prediction for a spheroid. R
 ecently\, our progress on predicting the stress profile on the surface of 
 a spheroid has been made. The results predicted by GLMT are verified by ge
 ometrical optics which has a more straightforward physical interpretation 
 of the mechanical effect of light. On the basis of GLMT\, influences of pa
 rticle’s non-sphericity and layer-structure\, as well as incident beam s
 hape on the stress profile can be known.
LOCATION:Edwards Room\, Bragg building\, Cavendish Laboratory
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