Analysis of Diffracted Mode Outcoupling in the Context of Amplified Spontaneous Emission of Organic Thin Films

Abstract

The existence of amplified spontaneous emission (ASE) is a fundamental principle of laser dyes. ASE indicates the spectral variation of the optical gain of a laser dye. Analyzing the spectral distribution of ASE is important for designing lasers. We demonstrate ASE investigations on planar waveguides made of a (co-)polymer. Similar to organic DFB (distributed feedback) lasers, a line grating allows a partial decoupling of the guided radiation. This decoupled radiation is detected as an indicator of the guided radiation. The diffraction of the radiation is utilized to perform a spectrally selective investigation of the ASE by spatially splitting it. This analysis method reduces the influence of isotropic photoluminescence and allows ASE to be analyzed across its entire spectrum. We were able to observe ASE in F8BT over a range from λASE,min = 530 nm to λASE,max = 570 nm and determine ASE threshold power densities lower than EASE< 2.57 μJ/cm2. The study of the power density of the ASE threshold is performed spectrally selectively.