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

Abstract

Here we report the fabrication and optical characterization of organic microcavities containing liquid-crystalline conjugated polymers (LCCPs): poly(9,9-dioctylfluoreneco-benzothiadiazole) (F8BT), poly(9,9-dioctylfluorene) (PFO) and poly(2,7-(9,9-dihexyl 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

Guest-responsive polaritons in a porous framework: chromophoric sponges in optical QED cavities

“…Higher values were only reported for nonplanar, more complex compounds, e.g. conjugated polymers ($65%) 10 and photoswitches ($32%). 43,44 The presence of strong coupling in the SURMOF-based microcavity is further supported by the outcome of experiments where absorption spectra were recorded for different angles of incidence (Fig.…”

“…The size of the Rabi splitting energy, D ¼ P+ À PÀ depends on the energy of the optical transition energy, absorption coefficient, and orientation of the transition dipole relative to the cavity. Recent progress in the eld of organic semiconductor (OSC) materials 10 suggest that subtle tuning of the transition dipole moment orientation can signicantly enhance Rabi splitting energies. 10,11 Whereas adjusting the optical transition energies of an individual organic chromophoric moiety is rather straight forward (e.g.…”

“…Recent progress in the eld of organic semiconductor (OSC) materials 10 suggest that subtle tuning of the transition dipole moment orientation can signicantly enhance Rabi splitting energies. 10,11 Whereas adjusting the optical transition energies of an individual organic chromophoric moiety is rather straight forward (e.g. by attaching appropriate side groups), the optical properties of the corresponding condensed molecular solid are difficult to predict because of cooperative effects and since even slight modication of the molecular structure can result in a completely different packing.…”

Transmissivity and Reflectivity of a Transverse‐Electric Polarized Wave Incident on a Microcavity Containing Strongly Coupled Excitons with In‐plane Uniaxially Oriented Transition Dipole Moments

“…Maxima 4 and 5 are not clearly resolved as the oscillator strength along e x is not intense enough following orientations of the PFO chains, as it was demonstrated in ref. [22] that the broad and unstructured emission from this structure confirmed weak coupling along e x . For ϕ ∈ 0 , 90 ½, the second lowest maximum in energy is the superposition of peaks 2 and 4, 0.05 eV apart in energy, whose respective broadenings allow for their mixing, with the overall maximum seemingly shifting to lower energies as ϕ is increased.…”

“…a) Schematic of the microcavity structure fabricated. The PFO chains A were oriented using the protocol presented in ref [22]…”