Abstract: A block of composite material includes a dielectric material with a dielectric constant of .epsilon..sub.d =4.66 and which is at least 4 .mu.m thick and has electrically conductive microparticles randomly distributed throughout. The composite material exhibits an optical bistability without cavity feedback. The microparticles must be nearly uniform in size and of spherical diameter much smaller than the wavelength of light in the particle. The composite, when illuminated by laser light in the range of 500 nm and of varying intensity, becomes opaque at a critical input intensity and stays opaque until the input intensity reaches a certain level both below and above the intensity at which it initially became opaque. Thus the material behaves as an optical switch and a limiter.