Low gain threshold of the cavity mode close to the cutoff wavelength in a three-slab asymmetric conjugated polymer-based waveguide structure

The emission mode close to the cutoff wavelength in a three-slab asymmetric (glass/polymer/air) conjugated polymer-based waveguide structure is characterized and found to be largely affected by microcavity effects. The spectral profiles of the emission as a function of viewing angle suggest that the peak emission is due to a cavity effect between the fully reflecting polymer-air interface and the highly reflecting polymer-glass interface. A low gain threshold (< 190 W cm(-2)) is found using conjugated benzothiadiazole-arylamine copolymer as the gain medium. The exceptionally low threshold is attributed to cavity enhancement effects. (c) 2006 American Institute of Physics.