Low‐Loss Organic Hyperbolic Materials in the Visible Spectral Range: A Joint Experimental and First‐Principles Study

Abstract

Hyperbolic media strengthen numerous attractive applications in optics such as super‐resolution imaging, enhanced spontaneous emission, and nanoscale waveguiding. Natural hyperbolic materials exist at visible frequencies; however, implementations of these materials suffer substantial compromises resulting from the high loss in the currently available candidates. Here, the first experimental and theoretical investigation of regioregular poly(3‐alkylthiophenes) (rr‐P3ATs), a naturally low‐loss organic hyperbolic material (OHM) in the visible frequency range, is shown. These hyperbolic properties arise from a highly ordered structure of layered electron‐rich conjugated thiophene ring backbones separated by insulating alkyl side chains. The optical and electronic properties of the rr‐P3AT can be tuned by controlling the degree of crystallinity and alkyl side chain length. First‐principles calculations support the experimental observations, which result from the rr‐P3AT's structural and optical anisotropy. Conveniently, rr‐P3AT‐based OHMs are facile to fabricate, flexible, and biocompatible, which may lead to tremendous new opportunities in a wide range of applications.

Metamaterial assisted illumination nanoscopy via random super-resolution speckles

“…1a. The ideal HMM has an unlimited k-space, while a practical HMM, made by Ag-SiO 2 multilayer, has a k-space limitation from its periodicity [23][24][25][26] . A multilayer with a smaller period of alternating layers supports a higher spatial frequency.…”

Unprecedented Fluorophore Photostability Enabled by Low‐Loss Organic Hyperbolic Materials

“…Herein, we demonstrate an unprecedented fluorophore photostability enabled by a self‐assembled organic hyperbolic material (OHM) film [ 28 ] in the visible spectrum. Compared to traditional HMMs [ 22,29,30 ] made of noble metal structures and other natural hyperbolic materials, [ 31–33 ] the OHMs used in this work feature a Lorentz‐type dispersion [ 33,34 ] with low‐loss natural hyperbolic polariton modes, [ 28 ] and thus support an extremely large LDOS and a large Purcell factor. [ 35 ] Moreover, this low‐loss hyperbolic nature of the OHM films also makes an efficient fluorescence enhancement without any outcoupling structure possible.…”

“…An OHM of regioregular poly(3‐hexylthiophene‐2,5‐diyl) (rr‐P3HT) was self‐assembled as described in ref. [ 28 ] . Figure S1a in the Supporting Information shows the complex permittivity of the fabricated rr‐P3HT OHM film measured by variable angle spectroscopic ellipsometry (VASE).…”

“…Figure S1a in the Supporting Information shows the complex permittivity of the fabricated rr‐P3HT OHM film measured by variable angle spectroscopic ellipsometry (VASE). The film features low‐loss hyperbolic behavior in the visible spectral range of 420–560 nm with the material figure of merit (FoM) −Re(ε H )/Im(ε H ) > 10, where ε H is the horizontal component of the complex permittivity [ 28 ] (see Section S2, Supporting Information). With such a large FoM, the hyperbolic polariton modes supported by the OHM give rise to an exceptionally strong Purcell effect, originating from the excitations of the nonradiative high momentum (high‐ k ) hyperbolic polariton modes (see Section S3, Supporting Information) and the radiative modes (see Sections S4 and S5, Supporting Information).…”

“…The OHMs used in this work provide PFs two orders of magnitude larger than the values found in those plasmonic materials, and even comparable to the values attained by using plasmonic nanostructures such as nanoantennae, [ 11,41 ] nanocavities, [ 53 ] and nanogratings [ 21,48 ] in the spectral range of 480–560 nm. Note that by exploiting the OHM's dispersion tunability, [ 28 ] the PF and the corresponding operating wavelength can be further optimized.…”