Jv. Ford et al., Refractive index dispersion functions of solid-phase polymers by multicolor optical diffraction, APPL PHYS L, 77(16), 2000, pp. 2515-2517
We show that fourth-order dispersion functions of solid-phase polymers can
be determined by multicolor optical diffraction. Electrodynamically trapped
microparticles of polyethylene glycol with different molecular weights wer
e probed by two-dimensional optical diffraction with four different laser w
avelengths (632.8, 514.5, 488.0, and 457.9 nm); subsequent Mie analysis of
one-dimensional scattering patterns yielded size and refractive index (both
real and imaginary parts). Using a single wavelength as a size reference,
the nonlinear dependence of the refractive index of solid (nonevaporating)
polymer microparticles was determined by finding the refractive index for a
given wavelength that best matched a Mie calculation subject to the refere
nce size constraint. The experimentally determined refractive index values
were fit to a standard fourth-order Cauchy function to obtain values for n(
0), n(1), and n(2). (C) 2000 American Institute of Physics. [S0003-6951(00)
04142-5].