Nanoimprinted organic distributed feedback lasers under pulsed and quasi-CW optical pumping

We have previously demonstrated organic semiconductor lasers with low lasing thresholds (P/sub th/=0.2 /spl mu/J/cm/sup 2/). The devices consist of an organic double-heterostructure waveguide with a distributed optical feedback provided by a 1/sup st/ order optical grating (200 nm period) fabricated by nanoimprinting. In this paper we report induced absorption effects found in the study of single layer distributed feedback (DFB) organic lasers under pulsed and quasi-CW optical excitations. These results agree qualitatively with our study of electrically pumped structures and have direct implications on development of diode lasers based on thin films of organic semiconductors.