Chiral organic photonics: self-assembled micro-resonators for an enhanced circular dichroism effect in the non-linear optical signal. Issue 47 (24th November 2017)

• Record Type: Journal Article
• Authors: Venkatakrishnarao, Dasari; Sahoo, Chakradhar; Mamonov, Evgeniy A.; Novikov, Vladimir B.; Mitetelo, Nikolai V.; Naraharisetty, Sri Ram G.; Murzina, Tatiana V.; Chandrasekar, Rajadurai
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 47(2017)
• Page Start: 12349
• Page End: 12353
• Publication Date: 2017-11-24
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc04621a
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Enantiomeric R and S type organic whispering-gallery-mode (WGM) optical micro-cavities display an enhanced CD-NLO effect due to increased light–matter interaction. Abstract : Chiro-optical signals from chiral molecules/structures are inherently weak. In particular, enhancing the circular-dichroism (CD) effect (different absorption of left or right circularly polarized light) in the non-linear optical (NLO) signal from chiral molecular materials is challenging and imperative since it is advantageous in various areas, from biomedical sciences to miniaturized photonic devices. Here we suggest and realize for the first time an approach to enhance the CD effect taking advantage of the NLO effects resonantly enhanced in the nonlinear chiral organic micro-resonators. These R - and S -type resonators in the form of micro-spheres are prepared by the self-assembly technique from the corresponding axially chiral enantiomeric molecules, namely R - and S -4-[2, 2′-diethoxy-6′-(4-formylphenyl)-[1, 1′-binaphthalen]-6-yl]benzaldehyde in CHCl3 /MeOH mixtures. Each enantiomeric micro-sphere, upon optical pumping, acts as a whispering gallery mode (WGM) resonator as the photo-luminescence (PL) is excited in a single- or in a two-photon regime. We show that the NLO-CD effect and the two-photon absorption (TPA) in the case of micro-spheres are at least twice as high as compared to a continuous film of the same effective thickness. This is due to pronounced field localization effects in micro-spheres with high Q -factor, which increases the photon residence time ( τ P ) in a chiral medium and thus strengthens the light–matter interaction. Finite-difference time-domain (FDTD) numerical calculations confirm a strong light localization near the boundary of the micro-spheres.