Inorganic Chiral Optical Materials

Recent advances in birefringent thin-film technology have led to vacuum-deposited inorganic chiral materials of significance for optics. The new materials have a double-start-screw nanostructure and exhibit large optical activity. At the circular Bragg resonance, which can be engineered for visible or near infrared wavelengths, the materials tend to transmit circularly polarized light of one handedness and reflect the other. A large range of standard thin-film materials can be used, but best results are achieved with evaporants that yield large form birefringence, such as tantalum oxide, titanium oxide, and zirconium oxide for visible wavelengths and silicon for the near infrared. Multilayered fabrication has been demonstrated, and potential applications include solid-state sources, reflectors, filters, and detectors for circularly polarized light.