Circularly polarised lasing from all-solid organic semiconductor activated external distributed feedback based on polarisation grating

An all-solid organic semiconducting conjugated polymer poly(2-methoxy-5-(2MODIFIER LETTER PRIME-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV) activated polarisation grating (PG) laser was demonstrated for the first time. The PG structure was fabricated based on photoalignment and stacking of multiple reactive mesogen sublayers to provide distributed feedback, and the thin MEH-PPV layer on top acts as the gain medium covered by a protecting layer. Light generates in waveguide mode from the active layer and spreads into the PG structure by an evanescent wave to get stimulated amplification. Using MEH-PPV as the gain medium with high photoluminescence quantum yield and large cross-section for stimulated emission, low threshold PG lasing was obtained. The momentum conservation in the plane of waveguide allows lasing coupled into the free space at certain angle instead of from the sample edge. Therefore, the intrinsic polarisation of the laser emission can be preserved and the circularly polarised lasing property was demonstrated by the PG laser.