  The polarized fluorescence emission of organic fluorophores has been
extensively studied in photonics and is increasingly exploited in single
molecule scale bio-imaging. Expanding the polarization properties of compact
molecular assemblies is, however, extremely challenging due to depolarization
and quenching effects associated with the self-aggregation of molecules into
the sub-nanometer scale. Here we demonstrate that Boron Nitride Nanotubes
(BNNTs) can act as a 1D host-template for the alignment of encapsulated
a-sexithiophene (6T) inside BNNTs, leading to an optically active 6T@BNNT
nanohybrid. We show that the fluorescence from the nanohybrid is strongly
polarized with extinction ratios as high as 700 at room temperature. A
statistical analysis of the 6T orientation inside BNNTs with inner diameter up
to 1.5 nm shows that at least 80% of the encapsulated 6Ts exhibit a maximum
deviation angle of less than 10{\deg} with respect to the BNNT axis. Despite a
competition between molecule-molecule and molecule-BNNT adsorption in larger
BNNTs, our results also show that more than 80% of the molecules display a
preferential orientation along the BNNT axis with a deviation angle below
45{\deg}.
