Measurement of the index of refraction of single microparticles.
The refractive index of single microparticles is derived from precise measurement and rigorous modeling of the stiffness of a laser trap. We demonstrate the method for particles of four different materials with diameters from 1.6 to 5.2 microm and achieve an accuracy of better than 1%. The method greatly contributes as a new characterization technique because it works best under conditions (small particle size, polydispersion) where other methods, such as absorption spectroscopy, start to fail. Particles need not be transferred to a particular fluid, which prevents particle degradation or alteration common in index matching techniques. Our results also show that advanced modeling of laser traps accurately reproduces experimental reality.
Knöner
Gregor
G
Centre for Biophotonics and Laser Science, School of Physical Sciences, The University of Queensland, Brisbane QLD 4072, Australia.
Parkin
Simon
S
Nieminen
Timo A
TA
Heckenberg
Norman R
NR
Rubinsztein-Dunlop
Halina
H
D008954:Models, Biological; D008956:Models, Chemical; D008962:Models, Theoretical; D010316:Particle Size; D012031:Refractometry