Stimulated resonance Raman scattering from epitaxially oriented crystals of biphenyl-capped thiophene

Spectrally narrowed light emission based on stimulated resonance Raman scattering has been observed for epitaxially grown needle crystals of a biphenyl-capped thiophene oligomer. Under optical pumping with a wavelength-tuned pulse laser, the crystals emitted a couple of sharp lines (full width at half maximum ∼0.3 nm) along the direction of the needle axis. In particular, the intense line with a Raman shift of 1435 cm−1 appeared at low excitation energy of a few μJ/pulse. This Raman line was assigned as the symmetric in-plane stretching mode of the molecule. The observed Raman-associated lasing suggests the presence of polaritonic interaction between the uniaxially ordered molecular excitons and emitted photons.