Azobenzene based surface relief gratings for thin film distributed feedback lasers

Holographic surface relief gratings written in azobenzene containing films were studied for the use as masters for polymeric thin film distributed feedback (DFB) lasers. Light induced mass transport driven by E-Z isomerization in azobenzene containing materials have shown to be attractive for all optical and one-step fabrication of periodic surface structures with varying parameters for different optical applications. Based on new azobenzene materials and their holographic processing deep surface relief gratings were generated with grating pitches in the range of 400 nm as resonant structures for second order DFB lasers emitting in the VIS range. Nanoimprint techniques enabled multiple duplications of azobenzene master gratings in UV adhesives. The replicas were coated via spin casting with thin films of red light emitting polymer layers to form DFB thin film lasers. These active layers are guest-host-systems consisting of an UV-light absorbing conjugated polymer as host transferring its excitation via Forster resonant energy transfer to a red emitting conjugated polymer. Simple adjustment of grating depth via controlling of illumination time allowed it to investigate the influence of the corrugation depth and thereby the coupling of laser light and grating on the lasing behavior of second order DFB lasers in the red region. For this purpose multiple surface structures with different corrugation depths of up to 130 nm were generated holographically, duplicated and coated.