Enhancement of pump efficiency for an organic distributed feedback laser based on a holographic polymer dispersed liquid crystal as an external light feedback layer
Abstract
We report a low threshold, high energy conversion organic distributed feedback (DFB) laser based on a holographic polymer dispersed liquid crystal (HPDLC) grating as an external light feedback layer, specifically, by adopting an acrylate-based monomer with low functionality and a rubbed polyimide (PI) alignment layer. In such configuration, the phase separated LCs were aligned along the preferred direction, which gave an increased refractive index difference between the LC and the polymer, so it can provide better light feedback in the HPDLC layer. The pump efficiency for the laser, such as lasing output threshold and conversion efficiency, can be enhanced. The light loss, diffraction efficiency and driving voltage were also investigated for the HPDLC structures to identify the effects of the rubbing layer and monomer functionality.