Complex refractive index from scattering measurements for an acoustically levitated single particle

Sample properties such as shape and size can be studied via light scattering, if the material complex refractive index is known. A numerical method which utilizes laboratory measurements for deriving the complex refractive index of a mm-sized single particle is introduced. The laboratory measurements are carried out using a $4\pi$ scatterometer that measures the intensity of polarized light scattered from an acoustically levitated sample in a fixed orientation as a function of scattering angle. To obtain the complex refractive index of the particle, measurements were compared to simulations done using a newly modified SIRIS4 Fixed Orientation geometric optics code. The real and imaginary part of the complex refractive index were varied in the simulations to find the best match between measurements and simulations. The complex refractive index of a levitated single particle was successfully derived in a specific wavelength using two different methods of translating sample orientation from measurements to simulations. For the first time, scattering matrix results from a measurement of a levitated mm-sized single particle in a fixed orientation were compared to light scattering simulations. The complex refractive index of a glass particle was derived successfully, verifying our method of refractive index retrieval from such measurements.