Abstract
Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth. Chiral molecules exhibit chiroptical responses, i.e., they have different electromagnetic responses to light of different circular polarizations. However, chiroptical responses in natural materials, such as circular dichroism and optical rotation dispersion, are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave. Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures, which however only leads to a limited performance. Herein, we show a new approach towards enhancement of chiroptical effects through a Fabry–Pérot (FP) cavity formed by two handedness-preserving metamirrors operating in the GHz region. We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude. Our approach may pave the way towards state-of-the-art chiral sensing applications.
Highlights
Chirality plays a significant role in chemistry and biology, and it dictates how pharmaceuticals, additives, pesticides, or agrochemicals, just name a few, are combined [1, 2]
Our simulations and measurements show that the FP cavity constructed by a pair of metasurface mirrors can improve the optical activity of the chiral molecule placing inside the FP cavity
The FP cavity has provided a wide range of applications such as laser resonators, optical wavemeters, dichroic filters, and add-drop multiplexers
Summary
Chirality plays a significant role in chemistry and biology, and it dictates how pharmaceuticals, additives, pesticides, or agrochemicals, just name a few, are combined [1, 2]. The chiroptical response of natural materials, is inherently low since the chiral molecule’s size is much smaller than the wavelength of electromagnetic (EM) wave [3] It shows that locally varying the distribution of the EM field may enhance the chiroptical effect of the weak chirality [4, 5]. The development of optical cavity made of microtoroid whispering-gallery resonators was proposed to increase the sensitivity of the biodetector [22] Our work extends this strategy by introducing a chiral Purcell effect through which the optical cavity can enhance chiroptical signals emitted from the biomolecules [3, 23]. The chiral response can be increased by the cavity possessing chiral-symmetric geometry, leading to a unidirectional lasing radiation in the far field [3] These methods rely on the precise positioning of chiral molecules to these nanoscale particles
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