Disclosed is a method for producing deposition particles or intermediate particles, characterized in that the method comprises: forming a solution comprising a solvent and one or more deposit sources, aerosolizing the formed solution to produce an aerosol of precursor particles comprising the deposit source, conditioning the precursor particles to produce deposition particles or intermediate particles from the deposit source and collecting said particles. The particles may be collected as a deposit or precursor deposit on a substrate. The particles may include a matrix material and a dopant. The conditioning may be quenched to produce a desired substructure. The matrix material may be essentially optically clear. The substrate may comprise an optical fiber or an optical fiber preform or