dichroische

Dichroische is the German term corresponding to the English word dichroic, describing materials that exhibit dichroism. Dichroism is the differential absorption of light depending on its polarization or the direction in which it travels through a material. As a result, a dichroic sample can appear to change color or brightness when viewed from different angles or under polarized light. The effect arises from anisotropy in a material’s electronic structure or from aligned microstructure that interacts differently with light along different axes.

There are two broad manifestations: linear dichroism, where absorption depends on the polarization state of light, and circular dichroism, where absorption differs for left- versus right-handed circular polarization. In solids, linear dichroism often appears in crystals with distinct optical axes or in oriented polymers and liquid-crystal systems. Circular dichroism is commonly associated with chiral structures in molecules or assemblies. Dichroism should be distinguished from birefringence, which involves differences in refractive (phase) velocity rather than absorption.

Dichroische materials are widely used in optics and instrumentation. Dichroic coatings and filters use thin-film interference to selectively transmit or reflect wavelengths, frequently with polarization dependence, enabling specialized photography, astronomy, and laboratory work. Polarizers and certain sunglasses rely on linear dichroic elements to control light. In nature, minerals such as tourmaline exhibit intrinsic dichroism.

See also: dichroism, polarizer, birefringence, thin-film interference.