Thin ferroelectric interferometers (TFI's) for use as light-modulating devices were fabricated entirely with thin-film techniques on sapphire substrates. The ferroelectric layer in the TFI devices was a lead lanthanum zirconated titanate thin-film material, which can be formed from a chemical solution on highly reflective dielectric mirror surfaces. Light intensity modulation in both transmission and reflection modes was demonstrated with the fabricated devices. Experimental data and simulations show that TFI devices possess tremendous potential in spatial light modulators because of their fast-switching, low-driving voltage and readiness for integration with a variety of substrates, including silicon.