Enhanced and Polarization Dependent Coupling for Photoaligned Liquid Crystalline Conjugated Polymer Microcavities

Florian Le Roux, Robert Anthony Taylor, Donal Bradley

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Here we report the fabrication and optical characterization of organic microcavities containing liquid-crystalline conjugated polymers (LCCPs): poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), poly(9,9-dioctylfluorene) (PFO) and poly(2,7-(9,9-dihexyl \newline fluorene)-co-bithiophene) (F6T2) aligned on top of a thin transparent Sulfuric Dye 1 (SD1) photoalignment layer. We extract the optical constants of the aligned films using variable angle spectroscopic ellipsometry and fabricate metallic microcavities in which the ultrastrong coupling regime is manifest both for the aligned and non-aligned LCCPs. Transition dipole moment alignment enables a systematic increase in the interaction strength, with unprecedented solid-state Rabi splittings of up to 1.80 eV, the first to reach energies comparable to those in the visible spectrum. With an optical gap of 2.79 eV for F6T2 this gives the highest-to-date organic microcavity coupling ratio, 65%. We also demonstrate that the coupling strength is polarization-dependent with bright polariton photoluminescence for TE polarization parallel to the polymer chains and either no emission or weakly coupled emission from the corresponding TM polarization.
Original languageEnglish (US)
Pages (from-to)746-758
Number of pages13
JournalACS Photonics
Volume7
Issue number3
DOIs
StatePublished - Jan 31 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The authors thank Professor Moritz Riede for access to research facilities and Dr Richard Hamilton and Professor Ruidong Xia for fruitful discussions. They also acknowledge funding from the University of Oxford, from the UK Engineering and Physical Sciences Research
Council and the Jiangsu Industrial Technology Research Institute. F.L.R. further thanks Wolfson College and Dr Simon Harrison for the award of a Wolfson Harrison UK Research Council Physics Scholarship.

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