  Organic exciton-photon polariton lasers have recently been shown to be
remarkable candidates for the realization of efficient sources of coherent
light operating at room temperature. While their thresholds are now comparable
with conventional organic photon lasers, tuning of molecular conformation and
orientation as a means to further enhance their performance remains largely
unexplored. Here, we first report a two-fold reduction in the threshold of a
polariton laser based on a high-Q microcavity filled with an active layer of
poly(9,9-dioctylfluorene) (PFO) when 15% {\beta}-phase conformation is
introduced. We then take advantage of the liquid crystalline properties of PFO
and use a thin transparent sulfuric dye 1 (SD1) photoalignment layer to induce
homogeneous nematic alignment of the polymer chains. The resulting transition
dipole moment orientation increases the Rabi energy, bringing the system into
the ultra-strong coupling regime where we observe anisotropic polariton lasing
with an eight-fold reduction in absorbed threshold, down to 1.14 pJ / 0.36
{\mu}Jcm-2 for the direction parallel to the orientation, with no emission
along the orthogonal direction. To our knowledge, this threshold is lower than
demonstrated with state-of-the art optically pumped organic vertical cavity
surface-emitting photon and polariton lasers. This demonstration opens new
opportunities for more efficient polaritonic devices and the observation of
fundamental effects at low polariton numbers.
