Separating the Material and Geometry Contribution to the Circular Dichroism of Chiral Objects Made from Chiral Media

Abstract

The chirality of an object can be studied by measuring the circular dichroism, that is, the difference in absorption of light with different helicity. The chiral optical response of an object, however, can have two different origins. On the one hand, it can be linked to the chiral geometry of the object. On the other hand, it can be linked to the chiral material from which the object is made. Whereas previously no distinction between the two contributions could be made, we report here a computational approach that allows us to separate these two contributions to the circular dichroism of an object. We consider separately the case where geometry-related resonances affect the optical response and the case where they are absent. In both cases, we find the circular dichroism to be easily decomposable if a geometrically achiral object has an absorption spectrum similar to that of the chiral object under investigation. Furthermore, in the nonresonant case, the contribution attributed to the material can be obtained without taking any geometry into account. Besides being of fundamental importance, the possibility of disentangling both contributions will be important for guiding the future design of chiral objects and devices.