Using holography to measure extinction.

This work presents a new concept to measure the extinction cross section for a single particle in situ. The concept involves recording the hologram produced by the interference of a particle's forward-scattered light with the incident light. This interference pattern is fundamentally connected to the energy flow that gives rise to extinction, and, by integrating this measured pattern, one obtains an approximation for the cross section. Mie theory is used to show that this approximation can be as little as 1% in error of the true value for many cases of practical interest. Moreover, since an image of the particle can be computationally reconstructed from a measured hologram using the Fresnel-Kirchhoff diffraction theory, one can obtain the cross section simultaneously with the particle shape and size.