Analysing Gain for Organic Laser Applications

Abstract

This thesis presents the results of a study into the design and characterisation of optically pumped organic semiconductor lasers for hybrid organic/inorganic applications. The study involves a detailed investigation into a broad range of materials including conjugated polymers and monodisperse oligomer molecules with emissions spanning the visible spectrum. To make viable electrically pumped organic semiconductor lasers using a hybrid system, it is essential that their lasing thresholds are reduced as far as possible.

The optical properties of two main families of oligomer and one conjugated polymer are investigated and the effect of their conjugation on stimulated emission discussed. Gain measurements based on one oligomer and the polymer are performed to assess the reliability of current gain extraction techniques and a new variant of an existing gain extraction experiment introduced. A second oligomer was optically- pumped to illustrate the phenomenon of random lasers and explicitly show how modes can develop in different ways depending on how their optical pump source is varied.

Lasers based on the green-emitting polymer were optically-pumped and wavelength tuning of their emission was demonstrated by altering both the grating duty cycle and the polymer film thickness allowing us to tune the wavelength to a region with a lower lasing threshold.

Finally, first imaged optical pump experiments using micro-LED arrays were performed. Micro-LED emission was imaged to replicate optimum pump conditions.