N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine Based Distributed Feedback Lasers with Holographically Fabricated Polymeric Resonators

The molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD) has been widely used in optoelectronic applications, mainly for its hole-transporting properties, but also for its capability to emit blue light and amplified spontaneous emission, which is important for the development of organic lasers. Here, we report deep-blue-emitting distributed feedback (DFB) lasers based on TPD dispersed in polystyrene (PS), as active media, and dichromated gelatin layers with holographically engraved relief gratings, as laser resonators. The effect of the device architecture (with the resonator located below or on top of the active layer) is investigated with a dye (TPD) that can be doped into PS at higher rates (up to 60 wt%), than with previously used dyes (<5 wt%). This has enabled changing the index contrast between film and resonator, which has an important effect on the laser performance. With regards to thresholds, both architectures behave similarly for TPD concentrations above 20 wt%, while for lower concentrations, top-layer resonator devices show lower values (around half). Remarkably, the operational durability of top-layer resonator devices is larger (in a factor of around 2), independently of the TPD concentration. This is a consequence of the protection offered by the resonator against dye photo-oxidation when the device is illuminated with pulsed UV light.

Применение термообработки при формировании рельефно-фазовых голографических структур на бихромированном желатине

A new method is proposed for the formation of a relief phase holographic structure on layers of dichromated gelatin (DCG). The method is based on the application of two types of alternative effects on gelatin: structuring using selective light tanning with coherent radiation from a He-Cd laser and destruction by irradiating the layers with short-wave UV radiation. To obtain highly effective holographic relief structures in the region of high spatial frequencies, up to 1500 mm–1, a time-shortened water treatment of samples, interrupted by an isopropanol bath, was previously proposed. In this paper, it is proposed to abandon the water treatment of DCG layers and replace it with heating the sample during irradiation with short-wave UV radiation. In the course of experiments, a steady increase in the diffraction efficiency was obtained regardless of the spatial frequency and thickness of the DCG layer, which is explained by the formation of a relief holographic structure due to evaporation and shrinkage of gelatin areas destroyed by UV radiation under the influence of high temperature.

Holographic Structure Transfer from Dichromated Gelatin Layers to a Polymethylmethacrylate Substrate

.