We use intensity modulated laser sources throughout the visible and near infrared spectral range with modulation frequencies from 10 MHz well beyond 1 GHz to generate Photon Density Waves in strongly light scattering materials.

Detection and analysis of PDWs in terms of amplitude and phase with respect to modulation frequency and source-detector distance allow for the precise determination of fundamental optical properties of the material under investigation, namely the absorption and reduced scatttering coefficients. Whereas the first provides access to chemical concentrations, the latter allows for the determination of concentrations or particle and droplet sizes of the dispersed phase without any dilution or calibration.

The analysis is based on radiation transport theory, Mie theorie and several approaches concerning dependent scattering. Don't worry - we know about the details!