Polarized measurements of spectrally narrowed emissions from a single crystal of a thiophene/phenylene co-oligomer

The spectrally narrowed emissions (SNE) from a flat single crystal of a thiophene/phenylene co-oligomer were investigated in a series of polarized measurements. The SNE spectra comprise of two major lines occurring at 507 and 514 nm. Of these, the former line effectively causes the emission gain narrowing by the pulse laser excitation polarized along the c axis. The intensity of the SNE is nearly isotropic with the radial directions along the flat crystal plane paralleling the bc plane. The SNE is strongly polarized along the a axis with its emission polarization ratio of the a axis to the b axis being 16.7. These polarized SNEs can be understood by the upright configuration of the molecular long axis paralleling the a axis. (c) 2007 American Institute of Physics.