Toward Chiral Sensing and Spectroscopy Enabled by All‐Dielectric Integrated Photonic Waveguides

• Published in: Laser & photonics reviews 2020-09, Vol.14 (9), p.n/a
• Main Authors: Vázquez‐Lozano, J. Enrique, Martínez, Alejandro
• Format: Article
• Language: English
• Subjects: chiral sensing; Chirality; chiroptical spectroscopy; circular dichroism; Circular polarization; Dielectrics; Integrated optics; integrated photonics; Miniaturization; Nanostructure; optical chirality; Photonics; Polarized light; Spectroscopy; Spectrum analysis; Waveguides
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.201900422

Chiral spectroscopy is a powerful technique enabling to identify optically the chirality of matter. So far, most experiments to check the chirality of matter or nanostructures have been performed through arrangements wherein both the optical excitation and detection are realized via circularly polarized light propagating in free space. However, for the sake of miniaturization, it would be desirable to perform chiral spectroscopy in photonic integrated platforms, with the additional benefit of massive parallel detection, low‐cost production, repeatability, and portability. Here it is shown that all‐dielectric photonic waveguides can support chiral modes under proper combination of fundamental eigenmodes. Two mainstream configurations are investigated: a dielectric wire with square cross section and a slotted waveguide. Three different scenarios in which such waveguides could be used for chiral detection are numerically analyzed: waveguides as near‐field probes, evanescent‐induced chiral fields, and chiroptical interaction in void slots. In all the cases, a metallic nanohelix is considered as a chiral probe, though all the approaches can be extended to other kinds of chiral nanostructures as well as matter. These results establish that chiral applications such as sensing and spectroscopy could be realized in standard integrated optics, in particular, with silicon‐based technology. So far, prevailing chiroptical applications have been performed upon free‐space excitation and detection schemes. Following the current trend toward miniaturization and integration of photonic devices, this work addresses the existence of chiral modes supported by lithographically defined photonic waveguides, and its potential for chiroptical applications such as sensing and spectroscopy, further expanding the portfolio of spectroscopic techniques in integrated platforms.