Open AccessApplication of the discrete dipole approximation to optical trapping calculations of inhomogeneous and anisotropic particles
Author(s) -
Stephen H. Simpson,
Simon Hanna
Publication year - 2011
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.016526
Subject(s) - optical tweezers , discrete dipole approximation , spheres , birefringence , physics , trapping , dipole , anisotropy , optics , symmetry (geometry) , context (archaeology) , optical force , particle (ecology) , materials science , molecular physics , quantum mechanics , geometry , ecology , paleontology , oceanography , mathematics , astronomy , biology , geology
The accuracy of the discrete dipole approximation (DDA) for computing forces and torques in optical trapping experiments is discussed in the context of dielectric spheres and a range of low symmetry particles, including particles with geometric anisotropy (spheroids), optical anisotropy (birefringent spheres) and structural inhomogeneity (core-shell spheres). DDA calculations are compared with the results of exact T-matrix theory. In each case excellent agreement is found between the two methods for predictions of optical forces, torques, trap stiffnesses and trapping positions. Since the DDA lends itself to calculations on particles of arbitrary shape, the study is augmented by considering more general systems which have received recent experimental interest. In particular, optical forces and torques on low symmetry letter-shaped colloidal particles, birefringent quartz cylinders and biphasic Janus particles are computed and the trapping behaviour of the particles is discussed. Very good agreement is found with the available experimental data. The efficiency of the DDA algorithm and methods of accelerating the calculations are also discussed.