Fabrication of volume scattering diffusers by spin-coating SiO2 microspheres and SU-8 photoresist for speckle reduction investigation

Volume scattering diffusers (VSDs) with different thicknesses were fabricated for speckle reduction investigation in a two-diffuser system. The VSDs were obtained by spin-coating the mixture of SiO2 microspheres and SU-8 photoresist, where the monodispersed SiO2 microspheres were synthesized by the Stöber method with an average diameter of 1.43 µm. The Mie scattering effect of the VSDs was observed owing to the refractive index difference between the SiO2 microspheres and the SU-8 photoresist. The speckle reduction effect of the two-diffuser system comprising cascaded stationary and moving VSDs was experimentally studied. The result can be used in designing more effective speckle reduction techniques in laser displays.