Abstract: Optical modulators and switches for use in telecommunications systems are disclosed having solid-state crystalline optical material comprised of III-V, II-VI, and IV semiconductor nanocrystals embedded in a polymer matrix. In a preferred embodiment, the crystalline material comprises CdSe crystals sized at less than 5.8 nm in diameter and more preferably at less than about 4 nm in diameter and advantageously embedded in poly(vinyl pyridine). The crystalline material sandwiched between two electrodes defines an optical modulator. In one preferred embodiment, the crystalline material with ten-percent crystal embedded in a polymer will exhibit with an applied voltage of 100V, a differential absorbance spectra (.DELTA.A) of about 50 cm.sup.-1 at wavelengths of about 610 nm and a differential refractive index (.DELTA.n) of about 10.sup.-4 at wavelengths of about 625 nm.