In one general aspect, a particle characterization instrument is disclosed that includes a first spatially coherent light source with a beam output aligned with an optical axis. A focusing optic is positioned along the optical axis after the coherent light source, and a sample cell is positioned along the optical axis after the focusing optic. The instrument also includes a diverging optic positioned along the optical axis after the sample cell, and a detector positioned outside of the optical axis to receive scattered light within a first range of scattering angles from the diverging optic. In another general aspect, an instrument can direct at least a portion of a first beam and at least a portion of a second beam along a same optical axis and a can receive scattered light from the sample cell resulting from interaction between the sample and either the first beam or the second beam.